Texas Tech University

 Overview and Introduction to Texas Mammals

This book is devoted to mammals, which are the class of vertebrate animals possessing diagnostic characteristics such as hair, females that have milk-secreting glands, and specialized teeth. One group of mammals, the cetaceans (whales and dolphins), possess a layer of blubber instead of hair. Mammals, having among their representative genera certain species that fly and others that glide, swim, climb, burrow, leap, or run, are perhaps the most versatile and adaptable of the vertebrate animal groups in Texas.

The importance of Texas in relation to geography and wildlife is no accident. Within the state is such a wide variation of soils, climate, and topography that the resultant vegetation and animal life are unusually rich. This diverse environment supports a resident fauna of 145 species of native terrestrial mammals, a number exceeded in the United States only by California and New Mexico. Since the publication of the last edition of this book in 2004, one new native species, Hall's pocket gopher (Geomys jugossicularis) has been added to the Texas fauna. Also, the two small foxes in western Texas (Vulpes velox and Vulpes macrotis), which were treated as subspecies of a single species in the last edition, have now been split apart again and are treated as different species.

In addition to the native species that occur in the state, there are also roughly 18 nonnative species (exotics and feral species) that have been introduced accidentally (Japanese macaque, Macaca fuscata; house mouse, Mus musculus; black rat, Rattus rattus; and Norway rat, Rattus norvegicus) or intentionally (nutria, Myocastor coypus; red fox, Vulpes vulpes; feral pig, Sus scrofa; axis deer, Axis axis; fallow deer, Dama dama; sika deer, Cervus nippon; nilgai, Boselaphus tragocamelus; greater kudu, Tragelaphus strepsiceros; Eastern Thomson's gazelle, Eudorcas thomsonii; sable antelope, Hippotragus niger; scimitar-horned oryx, Oryx dama; common eland, Taurotragus oryx; aoudad, Ammotragus lervia; and blackbuck, Antilope cervicapra) by humans and have become established as a part of the free-living fauna. Two domesticated species (feral dogs, Canis familiaris, and cats, Felis catus) have taken up life in the wild state in many places and have significant effects on other mammals living in those areas. Finally, there are the five common livestock species (cattle, Bos taurus; goats, Capra hircus; sheep, Ovis aries; horses, Equus caballus; burros, Equus asinus; and the mule, Equus caballus × Equus asinus) that occupy rangelands across the state and impact conditions for all Texas mammals. An asterisk (*) beside the common name in species lists and species accounts indicates a nonnative species. In addition, two enigmatic species (woodchuck, Marmota monax, and California sea lion, Zalophus californianus) have been reported.

Of the native species, at least eight (gray wolf, Canis lupus; red wolf, Canis rufus; jaguar, Panthera onca; jaguarundi, Puma yagouaroundi; margay, Leopardus wiedii; black-footed ferret, Mustela nigripes; Caribbean monk seal, Monachus tropicalis; and grizzly bear, Ursus arctos) are now extinct and are no longer present in the state; another (the bighorn sheep, Ovis canadensis) became extinct but was subsequently reintroduced into the wild, although the reintroduced animals were not of the type that originally occurred in the state. Another five species (hairy-legged vampire bat, Diphylla ecaudata; southwestern little brown myotis, Myotis occultus; northern long-eared myotis, Myotis septentrionalis; North Atlantic right whale, Eubalaena glacialis; and the blue whale, Balaenoptera musculus) have been recorded in the state on only a single occasion and should be regarded as accidental (or extralimital) in occurrence. Three species (sei whale, Balaenoptera borealis; humpback whale, Megaptera novaeangliae; and tawny-bellied cotton rat, Sigmodon ochrognathus) may be regarded as enigmatic, and their status is not easily determined. Records of these species are few, and in many cases they have not been observed for several decades.

Terrestrial mammals in Texas belong to the orders Didelphimorphia (opossums), Cingulata (armadillos), Primates (primates), Lagomorpha (hares and rabbits), Soricomorpha (shrews and moles), Chiroptera (bats), Carnivora (carnivores), Perrisodactyla (odd-toed ungulates), Artiodactyla (even-toed ungulates), and Rodentia (rodents). In addition, Texas is bounded by the waters of the Gulf of Mexico, and 30 marine mammals of the orders Cetacea (whales and dolphins), Carnivora (suborder Caniformia, seals), and Sirenia (manatees) enter the coastal waters and have either been sighted in the bays and ocean or stranded on the beaches of the state. One of the seals, the Caribbean monk seal (Monachus tropicalis), is now extinct throughout its range. The number of families, genera, and species of Texas mammals in each of these groups is given in table 1.

Texas is a keystone in understanding the distributional patterns of recent mammals in the United States. Several species reach distributional limits within the state. The mammalian fauna includes many species that occur throughout the central United States, especially species associated with the central grasslands; other species are associated with the southeastern deciduous forests, many are characteristic of the desert regions of the Mexican Plateau and the southwestern United States, and a few are associated with the mountain regions of the western United States and the tropical regions of northeastern Mexico.

TABLE 1. The number of families, genera, and species of mammals in Texas. Table includes 26 introduced and feral domestic species for which accounts are provided in this book (1 primate, 5 rodents, 2 carnivores, 16 even-toed ungulates, and 2 odd-toed ungulates).

ORDER FAMILIES GENERA SPECIES
Didelphimorphia (Opossums) 1 1 1
Sirenia (Manatees) 1 1 1
Cingulata (Armadillos) 1 1 1
Primates (Primates) 1 1 1
Lagomorpha (Hares and Rabbits) 1 2 5
Soricomorpha (Shrews and Moles) 2 4 5
Chiroptera (Bats) 4 19 33
Carnivora (Carnivores)1 8 21 32
Perissodactyla (Odd-toed Ungulates) 1 1 2
Artiodactyla (Even-toed Ungulates) 5 18 23
Cetacea (Whales and Dolphins) 6 17 27
Rodentia (Rodents) 8 31 71
TOTALS 38 117 202

 

1Includes eight species that are now extinct in Texas.

Other notable features of the terrestrial mammalian fauna of Texas are the number of endemic species and the variability within species as reflected by the number of described subspecies. Six species are virtually confined in their distribution to Texas. There are currently 226 described subspecies of native terrestrial mammals in the state; 56 species are represented by more than one subspecies; 41 species are monotypic and subspecies are not recognized.

Diversity of Land Mammals

There is considerable change in the diversity of Texas mammals relative to geography. This is not surprising given the large size and configuration of the state, which results in pronounced gradients in temperature, precipitation, and other environmental conditions. Texas sits at the crossroads of five major North American biomes (Eastern Deciduous Forests, Great Plains, Coastal Prairies, Rocky Mountains, and Southwest Deserts), each of which comprises many different ecological regions and habitats (fig. 1).

Distribution patterns for mammalian species appear to differentiate along two major gradients: a dominant east-to-west gradient of decreasing precipitation and productivity and a south-to-north gradient of decreasing mean annual temperature, increasing winter cold, and increasing seasonal variation of temperature (figs. 1 and 2). Species richness of mammals increases consistently in the state from east to west. Major shifts in the diversity pattern are evident on either side of the Balcones Escarpment and between the western portion of the Edwards Plateau and the Mountains and Basins of the Trans-Pecos region. The pattern is much more irregular, without any general trend, along the north–south transect. Diversity is highest in the Escarpment Breaks of the High Plains, the Balcones Canyonlands of the Edwards Plateau, and the subtropical brushlands of the South Texas Plains but lowest in the coastal regions of the South Texas Plains.

Overall there are more species of mammals in the western, southern, and northwestern regions of Texas than elsewhere. There are fewer species in the eastern, coastal, and central parts of the state. The highest diversity of mammals exists in the Mountains and Basins, or Big Bend region, in the western reaches of the Trans-Pecos, and the lowest is in the eastern Gulf Prairies and Marshes along the coast and the central Texas woodlands. Other areas with high mammal diversity include the northern Panhandle and the Stockton Plateau, the eastern edge of the High Plains, and the Rio Grande Plains. Mammal species richness also is positively related to the number of vegetation types, the range of elevation, and the types and textures of soils.

Vegetational Areas of Texas 

Figure 1. The 10 vegetational areas of Texas and the location of two transects along which species diversity was analyzed. Gray shading indicates mammal diversity, with species richness increasing from light to dark. Inset represents the composite range extent for all Texas mammals. Sources: Vegetational regions from F. W. Gould, Texas Plants: A Checklist and Ecological Summary (Texas Agricultural Experiment Station, MP-585, 1962). Mammal diversity and inset map from E. A. Holt, K. E. Allen, N. C. Parker, and R. J. Baker, "Ecotourism and Conservation: Richness of Terrestrial Vertebrates across Texas" (Occasional Papers, Museum of Texas Tech University 201 [2000]:1–16).

Species Diversity Plots

Figure 2. Species diversity plots for the quadrants along the two transects illustrated in fig. 1. Solid line (A) is east–west transect; dashed line (B), north–south transect.

Two important generalizations are evident about the diversity of Texas mammals. First, there is no strong correlation between land area of the vegetation regions and species diversity (fig. 3). For example, the High Plains region is slightly larger in area than the Trans-Pecos region, yet it supports only half as many species of mammals. Second, those natural regions of Texas where vegetative and topographic heterogeneity are the greatest provide a broader spectrum of potential mammalian habitats and thus support a greater number of mammalian species.

Overall, an analysis of mammalian species ranges indicates constantly changing spatial configurations of species numbers and degree of sympatry. James Owen, a former doctoral student of DJS, has authored a series of papers about the spatial distribution patterns of Texas mammals. His analyses suggest that changes in mammalian community structure in Texas are the result of species-specific responses to environmental conditions rather than broadscale community responses. Moreover, Owen found that species turnover patterns are relatively even in both north–south and east–west directions. Owen's data also reveal some interesting patterns of species richness among different taxonomic groups of mammals. For example, variation in elevation is a strong positive predictor for species richness of all mammals, rodents, and bats, but a weaker predictor for carnivores. This can be attributed to an increase in the number of habitats present in areas with high levels of topographic relief. Surprisingly, productivity is negatively correlated with species richness for all groups except carnivores, which show a positive relationship. Texas carnivores show an initial increase in species richness with increased productivity, a peak at intermediate levels of productivity, and a decline at higher levels of productivity. Carnivores also displayed two other patterns not observed in other taxa. High levels of species richness are distributed over a greater area for carnivores, and carnivore communities are generally richer in species than those of other taxa. Both patterns can be explained by the larger geographic ranges of carnivores.

Species Logarithmic Plot

Figure 3. Plot of the number of species versus the area for each of the vegetative regions of Texas shown in fig. 1.

Geographic Distribution of Land Mammals

Texas may be conveniently arranged into four regions based on the ecological distribution of mammals. The regions are the Trans-Pecos, the Plains Country, East Texas, and the Rio Grande Plains (fig. 4). The Trans-Pecos region includes the Mountains and Basins country west of the Pecos River. The Plains Country includes the High Plains, Rolling Plains, Cross Timbers area, and the Edwards Plateau. Included within the East Texas region are the Pineywoods, Post Oak Savannah, Blackland Prairies, and Gulf Prairies and Marshes. The Rio Grande Plains encompasses the South Texas brushlands. The Balcones Escarpment serves as the major physiographic barrier separating the Plains Country from East Texas and the Rio Grande Plains. The boundary between East Texas and the Rio Grande Plains is positioned between the Guadalupe and San Antonio Rivers where pedocal and pedalfer soils meet.

Four Regions of Texas

Figure 4. Four regions of Texas based on the ecological distribution of mammals.

The distributional patterns of land mammals in Texas conform to five general patterns: (1) ubiquitous species that range throughout most, or all, of the state (included in this group are several species that are now extinct or whose distributions have shrunk markedly in the past 150 years; two species, the pygmy mouse and the armadillo, whose ranges have expanded in the last 100 years; and an introduced species, the red fox, which has spread over most of the state); (2) species that are distributed primarily in one of the four divisions of the state; (3) western species distributed in the Trans-Pecos and Plains Country; (4) western species distributed in the Trans-Pecos and Plains Country but that also occur on the Rio Grande Plains; and (5) eastern species distributed principally east of the 100th meridian. Mammals assigned to each of these categories are listed below. It should be noted that certain species occur slightly outside the boundaries of the category to which they have been assigned, as indicated by the comments in the various species lists.

The greatest number of unique elements in the mammal fauna of Texas occurs in the Trans-Pecos region. Approximately one-third, or 30, of the mammals that occur in the Trans-Pecos are primarily restricted in distribution to that region. Most of them are species characteristic of the arid Mexican Plateau and southwestern United States or the montane woodlands of the western United States. The fewest number of unique elements is from the Rio Grande region, with nine unique elements, most of which are characteristic of the tropical lowlands of northeastern Mexico and reach their northern distributional limits in South Texas. The next fewest number of unique elements (10) is found in the Plains Country and, with the exception of the black-footed ferret, all of these species are rodents. The 14 mammals unique to East Texas are species characteristic of the deciduous forests and coastal prairies of the southeastern United States, which reach their western distributional limits in Texas.

Mammals Generally Distributed throughout the State

• Virginia Opossum, Didelphis virginiana (absent from driest portions of the Trans- Pecos)

• Nine-banded Armadillo, Dasypus novemcinctus (absent from far West Texas)

• Black-tailed Jackrabbit, Lepus californicus (not in the Big Thicket of East Texas)

• Eastern Cottontail, Sylvilagus floridanus

• Brazilian Free-tailed Bat, Tadarida brasiliensis

• Hoary Bat, Aeorestes cinereus

• Big Brown Bat, Eptesicus fuscus (absent from a belt extending throughout

the center of the state)

• Silver-haired Bat, Lasionycteris noctivagans

• Eastern Red Bat, Lasiurus borealis

• Coyote, Canis latrans

• Common Gray Fox, Urocyon cinereoargenteus

• Red Fox*, Vulpes vulpes (absent from far western and southern Texas)

• Bobcat, Lynx rufus

• Jaguar, Panthera onca (now extinct in Texas)

• Mountain Lion, Puma concolor (absent from much of the former range except South Texas and the Trans-Pecos; recently expanding into central Texas and some coastal regions)

• Striped Skunk, Mephitis mephitis

• Long-tailed Weasel, Mustela frenata (absent from northern Panhandle)

• American Badger, Taxidea taxus (absent from extreme eastern Texas)

• Ringtail, Bassariscusastutus

• Northern Raccoon, Procyon lotor

• American Black Bear, Ursus americanus (once limited in distribution, currently expanding into East Texas, central Texas, and the Big Bend region)

• American Bison, Bos bison (now extinct in the state except for a remnant population in north–central Texas)

• White-tailed Deer, Odocoileus virginianus

• Feral Hog*, Sus scrofa

• American Beaver, Castor canadensis (absent from the High Plains and the Trans-Pecos except along the Rio Grande)

• Northern Pygmy Mouse, Baiomys taylori (absent from extreme northeastern Texas and the Trans-Pecos)

• White-footed Deermouse, Peromyscus leucopus

• North American Deermouse, Peromyscus maniculatus

• Fulvous Harvest Mouse, Reithrodontomys fulvescens (absent from the High Plains and Concho Valley)

• Hispid Cotton Rat, Sigmodon hispidus

• Hispid Pocket Mouse, Chaetodipus hispidus (not in the Big Thicket of East Texas)

Mammals Occurring Principally in the Trans-Pecos

• Davis Mountains Cottontail, Sylvilagus robustus

• Western Bonneted Bat, Eumops perotis

• Pocketed Free-tailed Bat, Nyctinomops femorosaccus

• Mexican Long-nosed Bat, Leptonycteris nivalis

• Western Yellow Bat, Dasypterus xanthinus

• Spotted Bat, Euderma maculatum

• Western Red Bat, Lasiurus blossevillii

• California Myotis, Myotis californicus (disjunct record from Rolling Plains)

• Fringed Myotis, Myotis thysanodes (disjunct record from Rolling Plains)

• Long-legged Myotis, Myotis volans (disjunct record from Rolling Plains)

• Yuma Myotis, Myotis yumanensis (disjunct record from Rio Grande Plains)

• Hooded Skunk, Mephitis macroura

• Bighorn Sheep, Ovis canadensis (native population extinct; nonnative subspecies reintroduced into several mountain ranges)

• Elk or Wapiti, Cervus canadensis (remnant populations occur in the Guadalupe and Davis Mountains as well as on private ranches in many parts of the state)

• Mogollon Vole, Microtus mogollonensis

• Mexican Woodrat, Neotoma mexicana

• Chihuahuan or Mearns's Grasshopper Mouse, Onychomys arenicola (a few records just east of the Pecos River)

• Brush Deermouse, Peromyscus boylii

• Cactus Deermouse, Peromyscus eremicus (also in extreme western part of Rio Grande Plains)

• Northern Rock Deermouse, Peromyscus nasutus

• Tawny-bellied Cotton Rat, Sigmodon fulviventer

• Yellow-nosed Cotton Rat, Sigmodon ochrognathus

• Desert Pocket Gopher, Geomys arenarius

• Chihuahuan Desert Pocket Mouse, Chaetodipus eremicus (a few records east of the Pecos River)

• Rock Pocket Mouse, Chaetodipus intermedius (one record north of the Pecos River)

• Nelson's Pocket Mouse, Chaetodipus nelsoni (one record from Webb County in South Texas)

• Merriam's Kangaroo Rat, Dipodomys merriami (a few records east of the Pecos River and one record from DeWitt County in South Texas)

• Banner-tailed Kangaroo Rat, Dipodomys spectabilis (also in southern part of High Plains)

• Texas Antelope Squirrel, Ammospermophilus interpres (range extends into the broken country just east of the Pecos River, and there is a record from Gaines County on the edge of the Llano Estacado)

• Gray-footed Chipmunk, Tamias canipes

Mammals Occurring Principally in the Plains Country

• Black-footed Ferret, Mustela nigripes (now extinct in Texas)

• Prairie Vole, Microtus ochrogaster (subspecies taylori)

• Texas Deermouse, Peromyscus attwateri

• Plains Pocket Gopher, Geomys bursarius

• Hall's Pocket Gopher, Geomys jugossicularis

• Jones's Pocket Gopher, Geomys knoxjonesi

• Llano Pocket Gopher, Geomys texensis

• Texas Kangaroo Rat, Dipodomys elator

• Plains Pocket Mouse, Perognathus flavescens (also in El Paso County)

• Thirteen-lined Ground Squirrel, Ictidomys tridecemlineatus (also in a narrow strip through central Texas from the Red River and Dallas region south to Corpus Christi and east to Atascosa County in South Texas)

Mammals Occurring Principally in the Rio Grande Plains

• Southern Yellow Bat, Dasypterus ega

• Ocelot, Leopardus pardalis (formerly more widely distributed)

• Margay, Leopardus wiedii (now extinct in Texas)

• Jaguarundi, Puma yagouaroundi (possibly extinct in Texas)

• Coues's Rice Rat, Oryzomys couesi

• Texas Pocket Gopher, Geomys personatus

• Strecker's Pocket Gopher, Geomys streckeri

• Gulf Coast Kangaroo Rat, Dipodomys compactus

• Mexican Spiny Pocket Mouse, Liomys irroratus

Mammals Occurring Principally in East Texas

• Swamp Rabbit, Sylvilagus aquaticus (a few records from the Edwards Plateau)

• Southern Short-tailed Shrew, Blarina carolinensis

• Rafinesque's Big-eared Bat, Corynorhinus rafinesquii

• Seminole Bat, Lasiurus seminolus (disjunct record from Val Verde County)

• Southeastern Myotis, Myotis austroriparius (disjunct record from central Texas)

• Prairie Vole, Microtus ochrogaster (subspecies ludovicianus, now extinct in Texas)

• Golden Mouse, Ochrotomys nuttalli

• Texas Marsh Rice Rat, Oryzomys texensis (also in coastal region of Rio Grande Plains)

• Cotton Deermouse, Peromyscus gossypinus

• Eastern Harvest Mouse, Reithrodontomys humulis

• Attwater's Pocket Gopher, Geomys attwateri (barely extends into the northern part of the Rio Grande Plains)

• Baird's Pocket Gopher, Geomys breviceps

• Southern Flying Squirrel, Glaucomys volans (barely enters the Cross Timbers area of the Plains Country)

• Eastern Gray Squirrel, Sciurus carolinensis (introduced population in Lubbock County on the High Plains)

Mammals Occurring Principally in West Texas

(Plains Region and Trans-Pecos)

• Pallid Bat, Antrozous pallidus (disjunct record from lower Rio Grande Valley)

• Townsend's Big-eared Bat, Corynorhinus townsendii

• Western Small-footed Myotis, Myotis ciliolabrum

• American Parastrelle, Parastrellus hesperus

• Kit Fox, Vulpes macrotis

• Swift Fox, Vulpes velox

• Grizzly or Brown Bear, Ursus arctos (now extinct in Texas)

• Mule Deer, Odocoileus hemionus

• White-toothed Woodrat, Neotoma leucodon

• Lacey's White-ankled Deermouse, Peromyscus laceianus (a record from Webb County in South Texas)

• Piñon Deermouse, Peromyscus truei (known only from the Guadalupe Mountains in the Trans-Pecos and Palo Duro Canyon in the Panhandle)

• Western Harvest Mouse, Reithrodontomys megalotis

• Plains Harvest Mouse, Reithrodontomys montanus (also in the Blackland Prairies of East Texas)

• Yellow-faced Pocket Gopher, Cratogeomys castanops (disjunct record from Cameron County in lower Rio Grande Valley)

• Botta's Pocket Gopher, Thomomys bottae

• Silky Pocket Mouse, Perognathus flavus

• Black-tailed Prairie Dog, Cynomys ludovicianus

• Rock Squirrel, Otospermophilus variegatus

Mammals Occurring Principally in Western Texas

(Trans-Pecos or Plains Region) and Rio Grande Plains

• Desert Cottontail, Sylvilagus audubonii

• Crawford's Desert Shrew, Notiosorex crawfordi

• Big Free-tailed Bat, Nyctinomops macrotis (two records from East Texas)

• Ghost-faced Bat, Mormoops megalophylla

• Mexican Long-tongued Bat, Choeronycteris mexicana

• Cave Myotis, Myotis velifer

• Gray Wolf, Canis lupus (now extinct in Texas)

• Hog-nosed Skunk, Conepatus leuconotus (Big Thicket population now extinct)

• Western Spotted Skunk, Spilogale gracilis

• White-nosed Coati, Nasua narica (also in Big Bend region of the Trans-Pecos and Padre Island)

• Pronghorn, Antilocapra americana (now extinct in Rio Grande Plains)

• Collared Peccary, Pecari tajacu

• Southern Plains Woodrat, Neotoma micropus

• Northern Grasshopper Mouse, Onychomys leucogaster

• North American Porcupine, Erethizon dorsatum

• Ord's Kangaroo Rat, Dipodomys ordii

• Merriam's Pocket Mouse, Perognathus merriami

• Rio Grande Ground Squirrel, Ictidomys parvidens

• Spotted Ground Squirrel, Xerospermophilus spilosoma

Mammals Occurring Principally East of the 100th Meridian

• Elliot's Short-tailed Shrew, Blarina hylophaga

• Least Shrew, Cryptotis parva (also occurs in the Plains Country)

• Eastern Mole, Scalopus aquaticus (also occurs in the northern Plains Country, and there is an old record from Presidio County)

• Northern Yellow Bat, Dasypterus intermedius

• Evening Bat, Nycticeius humeralis (disjunct records from Midland and Presidio counties)

• American Perimyotis, Perimyotis subflavus (a few records from the Plains Country and a recent record from the Trans-Pecos)

• Red Wolf, Canis rufus (now extinct in Texas)

• Eastern Spotted Skunk, Spilogale putorius (records from northern High Plains and Panhandle)

• Northern River Otter, Lontra canadensis (one record from the Panhandle)

• American Mink, Vison vison (one record from the northern Panhandle)

• Woodland Vole, Microtus pinetorum

• Eastern Woodrat, Neotoma floridana

• Common Muskrat, Ondatra zibethicus (also in Canadian, Pecos, and Rio Grande drainages)

• Nutria*, Myocastor coypus (still spreading westward)

• Eastern Fox Squirrel, Sciurus niger (extends westward into the Plains Country)

Mammals Endemic to the State

Six species of mammals are unique to Texas in the sense that most or all of their known geographic range is confined to the mainland and barrier islands of the state. They are

• Attwater's pocket gopher (Geomys attwateri)—known from East Texas (between the Brazos and San Antonio Rivers);

• Texas pocket gopher (Geomys personatus)—known from the barrier islands of Texas and Tamaulipas, Mexico, and the Rio Grande Plains;

• Strecker's pocket gopher (Geomys streckeri)—known from Zavala and Dimmit counties in South Texas;

• Llano pocket gopher (Geomys texensis)—known from 11 counties in the Texas Hill Country;

• Gulf Coast kangaroo rat (Dipodomys compactus)—known from the barrier islands of Texas and Tamaulipas, Mexico, and the South Texas Plains; and

• Texas kangaroo rat (Dipodomys elator)—known from 10 counties in the mesquite plains of north-central Texas and formerly 1 county in Oklahoma.

There are three species of mammals (hairy-legged vampire bat, Diphylla ecaudata; southwestern little brown myotis, Myotis occultus; and northern long-eared myotis, Myotis septentrionalis) whose occurrence in Texas is most likely accidental. Resident breeding populations of these species have never been discovered within the state. The Texas records for all three are far outside their main range, and only a single record exists for each in the state. Furthermore, all three are bats, which are well known for their wandering movements.

Mammals of the Barrier Islands of Texas

More than two-thirds of the 591 km (367 mi.) of Texas Gulf shoreline is composed of six major barrier islands (from north to south): Galveston, Matagorda, San Jose, Mustang, Padre, and South Padre Islands (fig. 5). The islands can be divided into three geographic groups based on the physical characteristics of the coastline. The first group includes Galveston Island, which is separated from the next island group by approximately 145 km (90 mi.). The second group includes Matagorda and San Jose Islands, which are occasionally joined at very low tide. They are separated from the third group by Aransas Pass, one of the most durable passes along the Texas coast. The third group includes Mustang, Padre, and South Padre Islands. Padre and South Padre were one island until 1957, when Mansfield Channel was dredged, and Mustang Island has had frequent connections with Padre Island during its history.

From the Gulf to the bay side, the habitat types of each barrier island grade from open, sandy beach to the dune ridges, then to coastal prairie dotted with freshwater to brackish ponds and marshes, and finally to salt marsh. The plant species within these habitats are similar from island to island, which is not surprising because the plants must be adapted to a lack of freshwater and have a tolerance of highly saline conditions. The barrier islands of Texas have a depauperate mammal fauna compared with that of the mainland Texas coast. Chris Hice (University of New Mexico) and DJS studied the mammal fauna of the barrier islands in comparison with the adjacent mainland areas. In total, 28 species have been sighted on one or more of the islands. On Galveston Island, only 8 of 42 (19%) potential species have colonized the island; in the Matagorda complex, the number is 10 of 46 (22%) on Matagorda Island and 9 of 46 (20%) on San Jose Island; and for the Padre complex the number ranges from 22 (49%) on Mustang Island to 23 of 45 (51%) of potential mainland species on Padre and South Padre Islands. Only four species of mammals (eastern cottontail, Sylvilagus floridanus; Texas marsh rice rat, Oryzomys texensis; hispid cotton rat, Sigmodon hispidus; and the northern raccoon, Procyon lotor) occur on all of the barrier islands. Three other species (fulvous harvest mouse, Reithrodontomys fulvescens; black-tailed jackrabbit, Lepus californicus; and coyote, Canis latrans) have invaded all of the islands except Galveston Island. The Virginia opossum (Didelphis virginiana) is present on all of the islands except the Matagorda complex. Most of the discrepancy between the numbers of species that occur on each island complex results from the absence of ground squirrels, heteromyid rodents, and pocket gophers on the northern two complexes of islands.

Texas Barrier Islands

Figure 5. The barrier islands of Texas.

In 2013 Jennifer Frey and her student Gerrad Jones from New Mexico State University published an extensive account of the mammals of Padre Island National Seashore. They reported a total of 62 species of nonmarine mammals (51 native and 11 introduced) from Padre Island and adjacent areas, including 25 species within the borders of Padre Island National Seashore. This number of species is considerably larger than the number on Galveston Island, which is not surprising given the larger size of Padre Island and the lower overall diversity of mammals available to colonize the islands in southeastern Texas (28) compared with the South Texas region (62).

A number of factors have influenced the faunal composition of the barrier islands, including hurricane events, the mainland species pool upon which the island draws, and the degree of isolation of the island from the mainland. Differences in species richness and composition among island complexes can be attributed to the diversity of the closest mainland area and the island size. Thus, it appears that the dearth of mammal species on the islands has not resulted from a lack of colonization events but rather from the mammals' inability to survive in the harsher island environments.

On 13 September 2008, Hurricane Ike struck the Texas coast, inflicting considerable damage on Galveston and Pelican Islands. During the event, most of Galveston was completely inundated by water. A year after the hurricane, in the fall of 2009, Chris Hice returned to the island to resample small mammals at the same locations where she had sampled them in 1995–1996 to assess the impacts of the hurricane on the mammal fauna. To her surprise, Hice (personal communication) found that the rodents were highly adaptive to the hurricane, which seemed to have no negative impact on their abundance. Hice noted that destruction of grasses resulting from the inundation of the island by saltwater resulted in fresh grass sprouting in December, so more hispid cotton rats (Sigmodon hispidus) were reproducing in the winter than normal and there were more of them. All other species were of roughly equal abundance as they were in winter 1995–1996. Large rafts of flotsam deposited black rats (Rattus rattus) and house mice (Mus musculus) in undeveloped areas of the island, such as the state park. Hispid cotton rats were absent from Pelican Island in 1996 but were captured there in 2009, and house mice were more common and spread throughout the coastal prairie habitat after the hurricane. Hice's data suggest that hurricanes may not have the devastating impacts on small mammal populations as previously thought.

Mammals in the Coastal Waters and Gulf of Mexico

The Gulf of Mexico is a small oceanic basin covering about 1.3 million square kilometers (half a million square miles) of the Atlantic Ocean bounded by the United States, Mexico, and Cuba. Texas forms the northwestern land boundary of the Gulf and includes 591 km (367 mi.) of coastline. The Gulf has only two openings: the Yucatan Channel, toward the Caribbean Sea, and the Straits of Florida, toward the southwestern North Atlantic. The Gulf is characterized by a wide, smooth, and gently sloping continental shelf that makes up about 35% of its surface. Another 40% is composed of deep canyons along the continental slope, and the remaining 25% is the deep ocean. Two major features dominate the Gulf of Mexico: the Loop Current of the western Gulf, and the Mississippi River, which deposits, from the river mouth, nutrients and sediment loads in a plume that covers several thousand square kilometers.

There are extensive human impacts in the Gulf, including offshore drilling and shipping; pollution from agricultural, municipal, and industrial runoff; and commercial fishing. The oil and gas industry in the Gulf is one of the most developed in the world, with most of the offshore leasing and development activities occurring in the central and western portions of the region. There are more than 3,000 platforms operating in waters up to 198 m (650 ft.) deep, and many rigs are drilling in waters greater than 975 m (3,200 ft.) deep. Additionally, there are over 40,234 km (25,000 mi.) of oil and gas pipeline on the sea floor of the Gulf. Overall, 55% of US crude oil production, 52% of natural gas production, and 48% of oil refinery capacity come from the Gulf of Mexico.

In 1954 Gordon Gunter wrote the first account of marine mammals in the Gulf, documenting 16 known species based on a historical accumulation of incidental sightings and strandings. The fauna generally was thought to be depauperate compared with other ocean areas. The impetus for systematic efforts to determine the distribution of the marine mammals in the Gulf of Mexico began with the need to meet mandates of the US Marine Mammal Protection Act, passed in 1972, which made it illegal to harm marine mammals. The marine mammals considered endangered were further protected by the US Endangered Species Act (ESA). The Southeastern United States Marine Mammal Stranding Network was established in 1977, followed shortly thereafter by the Texas Marine Mammal Stranding Network. Data on the distribution of offshore species in the deeper waters of the Gulf began to accumulate with the deployment of dedicated large-scale aerial and boat surveys that began in the late 1970s and continue to the present time. With the advent of the stranding networks, in conjunction with the observational information from the aerial and shipboard surveys, the information about marine mammals in the Gulf grew exponentially.

Thirty-one species (28 cetaceans, 2 carnivores, and 1 manatee) of marine mammals are now known or have been known from the Gulf of Mexico. Of the 28 cetacean species, 27 have been either stranded along the Texas or Louisiana coast or observed in the waters of the continental shelf or deeper waters in the northwestern and north-central Gulf and therefore could move into Texas waters. Accounts for these 27 species have been provided in this edition of The Mammals of Texas. Of the two carnivores, one (the Caribbean monk seal, Monachus tropicalis) is now extinct and the second (the California sea lion, Zalophus californianus) was introduced and occurred in the feral condition only during the past; for this reason, only brief accounts for these species are included in this edition. The West Indian manatee (Trichechus manatus) is the only sirenian in the Gulf, and although there have been recent sightings of manatees along our coast, there is no evidence that breeding populations of this endangered species ever existed along the Texas coast.

The cetacean fauna of the Gulf includes 7 mysticete, or baleen, whales and 21 ondontocete, or toothed, whales representing four families. The Gulf cetacean fauna is clearly not depauperate. Half of the genera and more than one-third of the cetacean species in the world have been recorded from the Gulf. At least five of the larger whales are now thought to be of accidental occurrence in the Gulf and not represented by resident populations.

The cetacean community in the northern Gulf is essentially tropical. With the exception of Atlantic spotted dolphins (Stenella frontalis) and clymene dolphins (Stenella clymene), which are endemic to warm Atlantic Ocean waters, and common bottlenose dolphins (Tursiops truncatus), sperm whales (Physeter macrocephalus), and killer whales (Orcinus orca), which have nearly cosmopolitan distributions, all species occurring in the Gulf of Mexico inhabit deep, warm temperate to tropical waters throughout the world. Cetaceans in the Gulf occur in two species assemblages that overlap in upper continental slope waters (between 200 and 1,000 m [656 and 3,281 ft.]). Common bottlenose dolphins and Atlantic spotted dolphins are the only two species commonly found in the nearshore bays and continental shelf waters (<200 m deep), whereas oceanic waters (>200 m deep) are routinely inhabited by about 20 species, most of which have pantropical distributions.

There are environmental problems in the Gulf of Mexico that could threaten marine mammals. Agricultural pesticide runoff is particularly heavy from the Mississippi River and other river systems that run into the Gulf, and about 30% of all petrochemical refining and fully 50% of hydrocarbon product production (paints and plastics) in the United States occur around the shores of Galveston Bay. Pollution problems are more prevalent in shallow waters near shore and could be especially deleterious to the common bottlenose dolphin (Tursiops truncatus). Bottlenose dolphins occasionally have suffered major die-off epidemics along the Texas shore; for example, 201 animals stranded in 1990, 245 in 1992, and 286 in 1994 (the average since 1987 in the nonpeak years is 128 stranded dolphins). The 1994 die-offs involved a strain of morbillivirus that was found in a number of animals. Almost all of the stranded dolphins exhibited abnormally high amounts of nontoxic lesions, growths, and other abnormalities in their body parts. Dan Cowan, a well-known pathologist at the University of Texas Medical Branch in Galveston, documented previously unknown abnormalities in these animals. It is not known if high levels of artificial toxins caused some of the deaths, but there is reason to be suspicious since high levels of heavy metals and polychlorinated products were found in body tissues. The dolphins and whales of deep water simply have not been studied enough to form reasonable conclusions on the health of individuals.

From November to March of 2012, more than 123 common bottlenose dolphins stranded in Galveston, Aransas, Calhoun, Kleberg, and Brazoria counties along the coast. The strandings over a 5-month period were more than the number expected for an entire year, causing the episode to be classified as an "unusual mortality event" requiring investigation. Scientists suspected a possible connection between the strandings and an algal red tide bloom that stretched along the entire Texas coast from September to January, but some of the stranded dolphins showed evidence of discolored teeth and lung and liver infections, suggesting they had been exposed to oil.

Offshore oil and gas exploration can definitely impact marine mammals. Disastrous oil spills, like the huge 1989 Exxon Valdez spill in southern Alaska, are drastically harmful to marine mammals that use fur to thermoregulate, such as sea otters, seals, and sea lions, as well as to toothed dolphins and whales, which have an oil-repellent skin over a thick blubber layer to thermoregulate. These animals can be forced to abandon normal feeding grounds to avoid oil on the surface. An oil spill in 1990 (the Mega Borg spill) off Galveston, Texas, however, showed that common bottlenose dolphins may not know how to avoid extensive oil-covered areas. Observations revealed that the dolphins repeatedly surfaced in even the very volatile fresh areas of a spill, areas in which humans become sick to their stomach in minutes and lung tissue becomes rapidly coated in oil volatiles. Under such conditions, their breathing apparatus would become clogged, and the animals would suffocate. Since offshore currents did not bring carcasses close to shore, it is not known how many dolphins succumbed to the Mega Borg spill, but it can be surmised that fatalities occurred.

On 20 April 2010 British Petroleum's Deepwater Horizon rig blew up in the northeastern Gulf of Mexico, killing 11 people and unleashing the worst environmental disaster in US history. More than 750 million liters (200 million gallons) of oil and 205,000 metric tons (225,000 tons) of methane fouled the ocean and Gulf coastlines. In addition to the oil, nearly 7.6 million liters (2 million gallons) of toxic dispersants were sprayed into the Gulf's waters. The Center for Biological Diversity has estimated the oil spill likely harmed or killed approximately 82,000 birds of 102 species, about 6,165 sea turtles, and up to 26,000 marine mammals, including common bottlenose dolphins (Tursiops truncatus), spinner dolphins (Stenella longirostris), melon-headed whales (Peponocephala electra), and sperm whales (Physeter macrocephalus). Oiled marine mammals were collected from west of Cameron, Texas, to Port St. Joe, Florida. Researchers reported that carcasses washed up daily and that half of the dead animals were stillborn or dead infant dolphins. Such spills massively degrade ecosystems and all of the wildlife dependent on those ecosystems. Clean-up efforts remove only a fraction of the persistent oil and gas spilled. The remainder of the oil, including millions of liters remaining in the Gulf, will continue to poison wildlife for generations, and it could be years before the full extent of the damage is known. To British Petroleum's credit, it spent more than US$13 billion to help clean up the oil and mitigate the damages.

Energy development and exploration, marine construction, and a wide variety of other marine operations can have potential impacts to marine species from exposure to anthropogenic noise sources such as seismic surveys, shipping, and pile driving. Marine mammals that use sound to communicate, navigate, and forage are of particular concern. Of particular concern in the Gulf of Mexico are possible impacts on sperm whales (Physeter macrocephalus). This is the most abundant large cetacean in the Gulf, with a larger population than the most common baleen whale, and it also is protected under the Marine Mammal Protection Act as well as being listed as endangered under the ESA. The Bureau of Ocean Energy Management has implemented seismic survey mitigation measures on all leases within the outer continental shelf region. The results demonstrate a high level of compliance with regard to implementing specific mitigation measures in order to minimize the potential impacts of sound on this protected species.

Historical Changes in the Texas Mammal Fauna

Texas is fortunate to have a good historical perspective about its mammal fauna. From 1889 to 1905 a team of federal scientists from the US Bureau of Biological Survey (forerunner of today's US Fish and Wildlife Service [USFWS]) surveyed the flora and fauna of the state, emphasizing mammals as the target group. Vernon Bailey, chief naturalist of the survey and director of field efforts in Texas, was one of the leading mammalogists of his era, and he summarized the results of the Texas survey in a 222-page 1905 publication titled Biological Survey of Texas. This publication constitutes the primary comprehensive study of Texas mammals at the end of the nineteenth century. By comparing the mammal fauna during Bailey's time with the fauna today, it is possible to make some general statements about past conditions and the extent of biological change in the twentieth century.

Texas Natural History: A Century of Change, written by DJS, describes the history of the biological survey and chronicles the magnitude of twentieth-century changes in the Texas mammal fauna. On a macroscale the diversity of mammals changed substantially during the twentieth century. There has been a substantial turnover in species composition, involving both a loss and a gain in species, since 1900. A significant number of mammals are now extinct, and a growing number of species are regarded as endangered and threatened. Almost 35% of the mammal species (50 out of 145 native terrestrial species) either have become extinct or have had subspecies or metapopulations become extinct, or they are rare and appear to face some sort of problem that potentially threatens their existence.

Among the most significant trends during the twentieth century, several are particularly important and worthy of discussion. These are briefly described below, but a more extensive explanation is provided in Texas Natural History: A Century of Change.

PROLIFERATION OF EXTINCTIONS

Species extinctions increased dramatically during the twentieth century. When Bailey published his work in 1905, the only extirpated mammals were the American bison (Bos bison), elk (Cervus canadensis), and Caribbean monk seal (Monachus tropicalis). During the course of that century, the grizzly bear (Ursus arctos), gray wolf (Canis lupus), red wolf (Canis rufus), black-footed ferret (Mustela nigripes), jaguar (Panthera onca), margay (Leopardus wiedii), and bighorn sheep (Ovis canadensis) all joined the list of extirpated species, and now it appears that the jaguarundi (Puma yagouaroundi) must be added as well.

A variety of factors can cause extinction, but in the case of these species, exploitation and habitat alteration by humans probably had more to do with their disappearance than any other single factor. Overhunting definitely seems to have caused the disappearance of the elk and American bison. Predator control activities probably had much to do with the extirpation of the gray wolf and the jaguar. The red wolf disappeared as a result of predator control efforts and the genetic effect of interbreeding with coyotes (Canis latrans). The black-footed ferret disappeared primarily as a result of destruction of black-tailed prairie dog (Cynomys ludovicianus) towns, which removed most of the ferret's natural food supply. The big factors in the decline of the bighorn sheep were competition with domestic sheep and the use of net-wire fences that prevented the sheep from wandering about from one mountain range to another. The margay and grizzly bear were probably only marginal in Texas and never represented by established breeding populations, and the jaguarundi was overwhelmed by habitat loss and fragmentation.

The Caribbean monk seal was the only seal native to the Gulf of Mexico. It was distributed tropically and limited to the Gulf of Mexico coast, the Yucatan Peninsula, the western Caribbean Sea, the Greater and Lesser Antilles, the Bahamas, and the Florida Keys. Its remains have been excavated from archeological sites in coastal Texas, supporting its possible occurrence in the western Gulf. As mentioned earlier in this chapter, this species is no longer considered to be a member of the Texas fauna as the species is known to be extinct throughout its entire geographic range.

DECLINES IN GEOGRAPHIC DISTRIBUTION AND POPULATION ABUNDANCE

A notable number of Texas mammals, including species of all sizes and life history traits, have undergone drastic range reductions and today occupy a mere scant portion of their former range. Examples of species that are now severely reduced in distribution or abundance include the pronghorn (Antilocapra americana), black-tailed prairie dog (Cynomys ludovicianus), muskrat (Ondatra zibethicus), and, to some extent, the mountain lion (Puma concolor).

The pronghorn once occurred over the western two-thirds of Texas, but the great herds that once roamed the Trans-Pecos and Panhandle regions were reduced to a mere handful by the early twentieth century. The decline was associated with overgrazing of grasslands by domestic livestock, uncontrolled hunting, and extensive cultivation of prairie habitat. The pronghorn is now restricted to isolated patches of suitable habitat from the Panhandle to the Trans-Pecos.

No Texas mammal has suffered more from population decline this century than has the black-tailed prairie dog. It has been estimated that in the early 1900s prairie dog colonies covered 40.5 million to 101.25 million hectares (100 million to 250 million acres) throughout North America. Such concentrations were a heavy drain on range vegetation, and ranchers enlisted the federal government to combat the prairie dogs. Using mainly strychnine-treated grain, the ranchers, along with government rodent control specialists, poisoned millions of prairie dogs. By 1960 the once overwhelming populations had been reduced to scattered, small colonies. More recently, sylvatic plague has devastated many of the remaining small colonies and has contributed significantly to the decline of black-tailed prairie dog populations across much of their range. Today, it is estimated that 98% of the population has been lost, and that only 300,000 black-tailed prairie dogs remain in Texas. Records indicate that prairie dog habitat declined 61% just in the last two decades of the twentieth century. At this rate of population decline and habitat fragmentation, prairie dog extinction could occur during this century.

Another interesting case is that of the muskrat (Ondatra zibethicus). In some regions of the state, such as the Panhandle and the Trans-Pecos, muskrat populations appear to have declined or even disappeared, whereas in other regions, particularly the upper Texas coast, they have invaded and increased in abundance. Their decline in the Panhandle and the Trans-Pecos was apparently a result of the reduction in the availability of natural surface water. Interestingly, T. Boone Pickens, who owns Mesa Verde Ranch adjacent to the Canadian River in Roberts County, has been restoring natural surface water all over his property, and a large population of muskrats now occur there.

Historically, mountain lions (Puma concolor) occurred virtually throughout the state. Years of predator control efforts by livestock producers, however, forced the remaining mountain lions into more remote areas, thinly populated by humans. Today, the largest mountain lion populations are in the desert mountain ranges of the Trans-Pecos, especially in the Big Bend region, and the dense brushlands of the Rio Grande Plains. Predator control efforts have slowed since about 1970, and lion populations now appear to be expanding (see species account for a full explanation).

Something is definitely impacting the diversity and ranges of skunks in Texas. Although the striped skunk (Mephitis mephitis) has continued to increase in numbers and geographic range, the other species of skunks have declined for reasons that are not completely understood. The endemic subspecies of the hog-nosed skunk (Conepatus leuconotus telmalestes) in the Big Thicket region of southeastern Texas apparently has completely disappeared from that region, and the South Texas subspecies (C. l. leuconotus) has shrunk so dramatically in distribution and range that it is rarely seen. The western subspecies of the hog-nosed skunk (C. l. mesoleucus) remains relatively common and appears to be holding its own. The apparent decline of the hooded skunk (Mephitis macroura) is even more puzzling. This species was evident in western Texas until the early 1970s and has rarely been sighted or collected since then, despite efforts by several mammalogists to document them. The two species of spotted skunks (Spilogale gracilis and S. putorius), once relatively common in the state, now are rare in most areas where they formerly occurred, and their current status in the state is unknown. All of the species of skunks in Texas are in need of serious study to determine the factors that may be causing their decline.

RANGE EXPANSIONS AND REGIONAL FAUNAL CHANGES

Since the beginning of the twentieth century, a number of mammals have expanded their ranges in Texas. Notable examples include the nine-banded armadillo (Dasypus novemcinctus), the northern pygmy mouse (Baiomys taylori), and the North American porcupine (Erethizon dorsatum). At the time that Bailey and the federal agents roamed the state, all of these species had restricted distributions, whereas today they are much more wide-ranging and common.

Documentation of range expansions has been very prevalent for bats in recent decades. Three species, the American perimyotis (Perimyotis subflavus), the evening bat (Nycticeius humeralis), and the Seminole bat (Lasiurus seminolus), previously thought to be confined to the eastern half of the state, have now been collected in far western Texas. Likewise, the Mexican long-tongued bat (Choeronycteris mexicana), previously known in the state on the basis of a single specimen in Hidalgo County, has now been recorded in multiple counties along the border and inland, suggesting its range also is expanding. These examples suggest the Rio Grande may be serving as a dispersal corridor, allowing eastern and southern species of mammals to expand their ranges gradually westward during the last decades.

Unfortunately, not much is known about microscale changes in diversity, such as reductions or expansions of geographic ranges, changes in species abundance and community structure, and extinctions of local populations and subspecies. From the evidence at hand, however, it seems obvious that the faunal composition in several areas of the state changed during the twentieth century.

DOCUMENTATION OF ADDITIONAL FAUNAL ELEMENTS AND DISCOVERY OF CRYPTIC SPECIES

Even though Bailey and the federal agents did a thorough job of documenting the mammal fauna of Texas at the end of the nineteenth century, mammalogists working in the state throughout the twentieth century continued to document additional species and subspecies, and the taxonomy of mammals has changed based on new information about the status of populations, subspecies, and species. Such taxonomic changes undoubtedly will continue as more is learned about the genetic relationships of mammalian populations.

Twenty-four additional species of mammals have been documented since the publication of Bailey's Biological Survey of Texas. Of these 24 species, almost two-thirds are bats. The primary reason for the addition of numerous bat species to the fauna is improvements in bat-collecting techniques during the last century, especially since the 1954 development of the use of mist nets for capturing bats. More recently, the western yellow bat (Dasypterus xanthinus) was documented from Brewster County and subsequently in four other localities in western Texas; this bat clearly represents a species that is expanding its distribution northward from Mexico.

Probably the most remarkable discovery of a new species of mammal during the last century was the documentation by Fred Stangl of Midwestern University of a third species of cotton rat (Sigmodon fulviventer, the tawny-bellied cotton rat) from an isolated population near Fort Davis in Jeff Davis County. The species was previously known from only southeastern Arizona and southwestern New Mexico. At this time, the extent of the tawny-bellied cotton rat's range and its relative abundance in Texas remain unknown.

The twentieth century also saw a dramatic shift in the philosophy for classifying mammals for the purpose of taxonomic designation. With the advent of modern techniques of genetics and molecular biology in the last three decades of the twentieth century, new tools became available to measure genetic (and evolutionary) relatedness among populations. These techniques allowed scientists to study chromosomes (called karyology) and the sequence of genes in animals. Likewise, new sophisticated techniques of statistics allowed for more refined assessments of morphology (called morphometrics) among populations of mammals. Based on the use of these new techniques, the 2004 edition of The Mammals of Texas included several newly recognized species, referred to as "cryptic species," because although they could not easily be differentiated on the basis of observed morphological characteristics, they were, in fact, genetically distinct and reproductively isolated, thus meeting the basic requirement for biological species distinctness.

The 2004 edition also included examples of taxa that were different enough morphologically to be called separate species but proved to be almost identical genetically and thus deemed fully capable of interbreeding and producing viable offspring. Modern taxonomists typically arrange such populations as different subspecies of the same species.

The best examples of cryptic species in Texas are found in the pocket gophers of the genus Geomys. Recent studies by specialists trained in cytological and molecular taxonomy have revealed the existence of six species of pocket gophers ranging over what was formerly considered the range of G. bursarius. These species (plains pocket gopher, G. bursarius; Attwater's pocket gopher, G. attwateri; Baird's pocket gopher, G. breviceps; Jones's pocket gopher, G. knoxjonesi; Llano pocket gopher, G. texensis, and Hall's pocket gopher, G. jugossicularis) are considered cryptic species, meaning they cannot be easily differentiated on the basis of observed morphological characteristics although they are genetically distinct and reproductively isolated. Although all of the species appear to be allopatric in range, karyotypic, electrophoretic, and mitochondrial DNA data are required to distinguish questionable specimens with confidence.

Similar instances of such cryptic species also were discovered in other groups of rodents, including deermice (genus Peromyscus), grasshopper mice (Onychomys), pocket mice (Chaetodipus), kangaroo rats (Dipodomys), shrews (Blarina), and dolphins of the genus Stenella. These types of discoveries, resulting from taxonomic revisions, accounted for much of the change in the taxonomy and classification of mammals during the twentieth century.

An example of the opposite situation included in the 2004 edition of The Mammals of Texas (that is, new taxonomic approaches have resulted in combining species formerly considered to be distinct and separate) involved the arid-land foxes of the genus Vulpes. For most of the twentieth century, arid-land foxes were regarded as two similar but separate species, the swift fox (V. velox) and the kit fox (V. macrotis), and that was the arrangement used by Bailey. A subsequent taxonomic study of these foxes based on advanced morphometric and protein-electrophoretic methods concluded, however, that the taxa were not sufficiently distinct to warrant separate species status. Thus, the two foxes were grouped into a single species, V. velox, comprising two subspecies, V. v. velox from the Panhandle and adjacent areas and V. v. macrotis from the Trans-Pecos. Ironically, using more modern molecular DNA data, these same scientists have now reversed their previous conclusion and consider these two foxes to be separate species (see next section).

Similarly, Jerry Dragoo, now at the University of New Mexico, Rodney Honeycutt of Texas A&M University, and DJS revised the taxonomic status of the hog-nosed skunks (genus Conepatus). Two species of hog-nosed skunks had been recognized in Texas, C. mesoleucus in western Texas and the Hill Country and C. leuconotus along the Texas coast. Using external and cranial morphology as well as mitochondrial DNA sequences, these authors concluded that hog-nosed skunks are represented by only a single species, for which the taxonomic name C. leuconotus has priority. The former designation of C. mesoleucus for the hog-nosed skunks of western and central Texas has proven to be no longer valid.

Finally, our understanding of higher taxa (above the species level) of mammals is being challenged by molecular genetics. Studies of gene sequences, subjected to phylogenetic analysis, are revealing different genera and even families of mammals. A classic example in Texas is represented by the big-eared bats of the genus Plecotus. In the earliest editions of The Mammals of Texas, these bats were arranged in the genus Corynorhinus, reflecting a division of the New World big-eared bats from the Old World big-eared bats of the genus Plecotus. Then, for reasons of morphological similarity, Charles Handley of the National Museum of Natural History lumped the two genera together and placed all species in the genus Plecotus. For the next several editions of The Mammals of Texas, the two Texas species were arranged in that genus. In 1992, however, a phylogenetic analysis of 25 morphological and 11 karyological characters suggested that Corynorhinus should be afforded generic distinction from Plecotus; more recently, a sequence analysis of mitochondrial genes has provided additional support for that taxonomic interpretation. Thus, in the 2004 edition the Texas species were once again placed in the genus Corynorhinus, where they remain today. We can expect more of these kinds of classification revisions as our knowledge of mammalian gene sequences increases.

RECENT CHANGES IN CLASSIFICATION AND TAXONOMY OF TEXAS MAMMALS

The most significant change in classifying mammals in this new edition of The Mammals of Texas comes from the continued use of DNA sequence data and the re-emergence of an old species concept, the genetic species concept (GSC). Sequence data from DNA offers a mechanism to examine genetic differences among populations of mammals and to determine the extent of genomic divergence between those populations. We have seen a proliferation of DNA sequence data since the latter part of the 1990s. As this technique has become less expensive and easier to perform (due to advances culminating from the Human Genome Project), it has become a staple methodology for many mammalian research laboratories.

The second significant change involves a conceptual shift away from the biological species concept (BSC), as championed by Ernst Mayr, toward a phylogenetic species concept, as described by Joel Cracraft. More recently, one of us (RDB) and his colleague at Texas Tech, Robert J. Baker, elevated awareness of the GSC proposed concept by Dobzhansky, Bateson, Mueller, and others during the early and mid-1900s. Baker and RDB defined a genetic species as a group of genetically compatible interbreeding natural populations that is genetically isolated from other such groups. Simply put, if a researcher can demonstrate consistent genetic differences between two groups, then those groups are genetically isolated and by extension are maintaining separate and distinct gene pools. In other words, the populations are not exchanging genes and are behaving as distinct species. In addition, the GSC infers that the more genetically distinct populations are, the longer the time frame required for that isolation to have taken place; thus older pairs of species would be expected to differ by a larger amount than would pairs of young species.

The advantage of the GSC is that it focuses on genetic isolation instead of reproductive isolation, as required by the BSC. Also, DNA sequence data provides a convenient means for testing genetic isolation, whereas reproductive isolation is more difficult to measure in natural populations. In short, examination of DNA sequence data under the framework of the GSC has led to several taxonomic revisions for Texas mammals in the last 20 years. Consequently, we have incorporated these changes into this version of The Mammals of Texas.

The major taxonomic changes made since the publication of the 2004 edition of The Mammals of Texas may be summarized as follows:

• Two additional orders, Primates and Perissodactyla, have been added to the list of Texas mammals because feral populations of each have been established in the state.
• We have followed taxonomic and phylogenetic experts in using Cingulata, instead of Xenarthra, as the ordinal name for the armadillos and in applying Soricomorpha as the ordinal designation for all North American shrews and moles.
• Based on gene sequence analysis within the Order Chiroptera, we recognize two new genera, with Pipistrellus being replaced by Parastrellus and Perimyotis.
• We followed the conclusions of experts in mammalian taxonomy and phylogeny in removing the jaguarundi from the genus Herpailurus and placing it in the genus Puma, as well as using Vison as the generic name for the American mink.
• We followed molecular evidence in treating Cervus canadensis and Cervus elaphus as separate species, with Cervus canadensis being included as part of the Texas fauna.
• The Caribbean Monk Seal has been considered extinct since 1952 and is now only briefly mentioned in our accounts.
• The following five introduced species of artiodactyl ungulates have established large, feral populations in many parts of Texas and consequently have been added to our checklist: Eudorcas thomsonii (Eastern Thomson's Gazelle), Hippotragus niger (Sable Antelope), Oryx dammah (Scimitar-horned Oryx), Taurotragus oryx (Common Eland), and Tragelaphus strepsiceros (Greater Kudu).
• Based on DNA sequence variation in marsh rice rats from the southern United States and Mexico, we now recognize two distinct genetic clades in Oryzomys palustris. Individuals from the southeastern United States are referred to O. palustris, whereas populations from the south-central United States, including Texas, are referred to O. texensis.
• Based on DNA sequence variation in white-ankled mice from the southern United States and Mexico, it has been concluded that Peromyscus pectoralis laceianus warrants specific recognition. Consequently, P. laceianus replaces P. pectoralis as the species in Texas.
• Recent DNA studies have demonstrated that the nutria rat (Myocastor coypus) is phylogenetically aligned with the spiny rats in the family Echimyidae. Therefore, in this edition we remove the family Myocastoridae and replace it with the family Echimyidae as a member of the Texas fauna.
• Data from studies of hybrid zones, chromosomes, DNA sequences, and biogeography provide evidence that another cryptic species of pocket gopher, Geomys jugossicularis, should be recognized from the northern Panhandle of the state.
• A recent revision of the ground squirrels of the genus Spermophilus has determined that the genus is not monophyletic. Now seven genera are required to reflect the phylogeny of the group adequately, and three of these (Ictidomys, Otospermophilus, and Xerospermophilus) should be applied to species in the Texas fauna.
• Based on molecular data, one of the ground squirrels species in Texas, Ictidomys mexicanus, has been split into two species, I. mexicanus and I. parvidens, with the latter being applied to the Texas populations. Consequently, we have removed I. mexicanus from our checklist of Texas mammals and added I. parvidens.

GROWTH IN THE NUMBER OF THREATENED, ENDANGERED, AND RARE SPECIES

Several land mammals are viewed as having some sort of biological issue that threatens or potentially threatens their existence. These are species that, in the opinion of biologists and conservation groups, currently face or likely will face serious conservation problems in the future.

Many of the species in jeopardy share life history attributes that make them especially vulnerable to local extinction events. Some species, such as bats, which have low reproductive rates, are slow to recover from population declines caused either by catastrophic events or by habitat destruction. Others, such as many of the carnivores and larger herbivores, are large in body size and have an extensive home range that, coupled with low population densities and their trophic level, make them highly vulnerable to human disturbance. Many have a confined geographic range, limited to a handful of locations, which makes them highly vulnerable to local extinction events. Another category of vulnerability includes those species dependent on some highly specialized but scarce resource. The organism may be a masterpiece of adaptation, but it is vulnerable because of one requirement within its habitat that must be met.

State and federal agencies as well as private organizations have developed lists of rare and endangered mammals. The USFWS publishes a list of endangered and threatened species that includes mammals listed in these categories in the Federal Register, and the Texas Parks and Wildlife Department (TPWD) has a list of protected nongame wildlife. These are the official lists governed by federal and state law, statutes, and regulations.

Additionally, the International Union for Conservation of Nature and Natural Resources (IUCN), founded in 1964, publishes the IUCN Red List of Threatened Species (Red List), which is the most comprehensive inventory of the global conservation status of biological species. In 2012 the IUCN completed an update of the status for all 5,488 mammal species in the world. This list includes information about each species' geographic range, ecology and habitat, extinction risk, and overall conservation status according to eight categories: extinct, extinct in wild, critically endangered, endangered, vulnerable, near threatened, least concern, and data deficient. In the case of mammals, this list was put together by the IUCN staff and a group of partners that included Arizona State University, Texas A&M University, University of Rome, University of Virginia, and the Zoological Society of London.

The legal protection of plants and animals considered to be endangered or threatened was not an issue during the time of Bailey and the federal agents. The concept of federal and state laws to protect wildlife was just taking root at the beginning of the twentieth century. It was only in the latter half of the century that federal and state laws were developed to protect nongame animal species, including invertebrates, and also plants. The first federal legislation in this area was the Endangered Species Preservation Act of 1966, replaced soon thereafter by the ESA of 1969, and culminating in congressional passage of the ESA of 1973, which was subsequently reauthorized in 1988 and amended in 1992, 1996, 2004, and 2009.

According to the USFWS, Texas ranks sixth in the nation in terms of the number of endangered species living within its borders. Forty-five animals and 27 plants protected under the ESA have been recorded from Texas, a number that reflects the state's large size, diverse array of habitats, and growing development pressures. According to a 1994 report, 39% of the endangered plant and animal species found in Texas were still declining, only 24% were judged to be improving or stable, and for the remaining 37% the USFWS lacked the resources to determine how they are faring.

In 1973 the Texas Legislature authorized the TPWD to establish a list of endangered and threatened animals in the state. Currently, TPWD lists 30 terrestrial Texas vertebrates as endangered, threatened, or extinct (table 2). Mammals included in the federal and state lists are distributed throughout the state as well as our coastal and offshore waters. There is no obvious geographic pattern or concentration of occurrence of these species, suggesting that the conservation pressures on our rare and endangered resources are statewide and not just regional or local in nature. Rare mammals occur in 54 of the 91 plant communities in Texas. Thirteen plant communities contain state or federal endangered mammals. These results demonstrate that no single habitat can be targeted for conservation of rare mammals in Texas.

Six land mammals currently are listed as endangered in Texas by both the USFWS and TPWD. Two of them (the Mexican long-nosed bat, Leptonycteris nivalis, and the ocelot, Leopardus pardalis) still have extant populations in the state. The other four species (red wolf, Canis rufus; gray wolf, Canis lupus; jaguarundi, Puma yagouaroundi; and jaguar, Panthera onca) listed as endangered by both agencies are now extinct in Texas, although there still may be some question about the jaguarundi. The black-footed ferret, Mustela nigripes, is listed as extirpated by TPWD and endangered by USFWS.

TABLE 2. Texas mammals with critical status as defined by the Texas Parks and Wildlife Department (TPWD), US Fish and Wildlife Service (USFWS), and International Union for Conservation of Nature (IUCN).

Scientific Name, Common Name

TPWD(state status)

USFWS (federal status) IUCN (global status)
Trichechus manatus, West Indian Manatee Endangered Endangered Vulnerable
Sylvilagus robustus, Davis Mountains Cottontail Not listed Not listed Endangered
Choeronycteris mexicana, Mexican Long-tongued Bat Not listed Not listed Near threatened
Leptonycteris nivalis, Mexican Long-nosed Bat Endangered Endangered Endangered
Corynorhinus rafinesquii, Rafinesque's Big-eared Bat Threatened Not listed Least concern
Dasypterus ega, Southern Yellow Bat Threatened Not listed Least concern
Euderma maculatum, Spotted Bat Threatened Not listed Least concern
Canis lupus,1 Gray Wolf Endangered Endangered Least concern
Canis rufus,1 Red Wolf Endangered Endangered Critically endangered
Leopardus pardalis, Ocelot Endangered Endangered Least concern
Leopardus wiedii,1 Margay Threatened Endangered2 Near threatened
Panthera onca,1 Jaguar Endangered Endangered Near threatened
Puma yaguaroundi, Jaguarundi Endangered Endangered Least concern
Spilogale putorius interrupta, Plains Spotted Skunk Not listed Under review Not listed
Mustela nigripes, Black-footed Ferret Extirpated Endangered Endangered
Nasua narica, White-nosed Coati Threatened Not listed Least concern
Ursusamericanus, American Black Bear Threatened T/SA3 (eastern);
not listed (western)
Least concern
Ursusamericanusluteolus, Louisiana Black Bear Threatened Threatened Not assessed
Ursusarctos, Grizzly or Brown Bear Extirpated Threatened Least concern
Bos bison, American Bison Not listed Not listed Near threatened
Eudorcasthomsonii, Eastern Thomson's Gazelle Not listed
(nonnative)
Not listed
(nonnative)
Near threatened
Oryxdammah, Scimitar-horned Oryx Not listed
(nonnative)
Endangered (North Africa) Extinct in wild
Ammotraguslervia, Aoudad Not listed
(nonnative)
Not listed
(nonnative)
Vulnerable
Antilopecervicapra, Blackbuck Not listed
(nonnative)
Not listed
(nonnative)
Near threatened
Eubalaenaglacialis, Northern Right Whale Not listed Endangered Endangered
Balaenopteraborealis, Sei Whale Not listed Endangered Endangered
Balaenopteramusculus, Blue Whale Not listed Endangered Endangered
Balaenopteraphysalus, Fin Whale Endangered Endangered Endangered
Megapteranovaeangliae, Humpback Whale Endangered Endangered Least concern
Feresaattenuata, Pygmy Killer Whale Threatened Not listed Data deficient
Globicephalamacrorhynchus, Short-finned Pilot Whale Threatened Not listed Data deficient
Orcinusorca, Killer Whale or Orca Threatened Endangered4 Data deficient
Pseudorcacrassidens, False Killer Whale Threatened Endangered Data deficient
Stenellafrontalis, Atlantic Spotted Dolphin Threatened Not listed Data deficient
Stenobredanensis, Rough-toothed Dolphin Threatened Not listed Least concern
Kogiabreviceps, Pygmy Sperm Whale Threatened Not listed Data deficient
Kogiasima, Dwarf Sperm Whale Threatened Not listed Data deficient
Physetermacrocephalus, Sperm Whale Not listed Endangered Vulnerable
Mesoplodoneuropaeus, Gervais's Beaked Whale Threatened Not listed Data deficient
Ziphiuscavirostris, Cuvier's Beaked Whale Threatened Not listed Least concern
Oryzomyscouesi, Coues's Rice Rat Threatened Not listed Least concern
Peromyscustrueicomanche, Palo Duro Deermouse Threatened Not listed Least concern
Geomysarenarius, Desert Pocket Gopher Not listed Not listed Near threatened
Dipodomyselator, Texas Kangaroo Rat Threatened Under review Vulnerable
Dipodomysspectabilis, Banner-tailed Kangaroo Rat Not listed Not listed Near threatened

1Species considered by the authors to be extinct in Texas.
2The USFWS status of endangered applies to populations in Mexico; former US population (subspecies cooperi) is not listed.
3Threatened, similarity of appearance.
4Endangered status applies to southern resident population along northwestern coast of USA; Gulf population is not listed.

Ten taxa of land mammals are regarded as threatened by the TPWD: southern yellow bat (Dasypterus ega), spotted bat (Euderma maculatum), Rafinesque's big-eared bat (Corynorhinus rafinesquii), Texas kangaroo rat (Dipodomys elator), Coues's rice rat (Oryzomys couesi), Palo Duro deermouse (Peromyscus truei comanche), American bear (Ursus americanus), Louisiana black bear (U. americanus luteolus), white-nosed coati (Nasua narica), and margay (Leopardus wiedii). The margay is now extinct in Texas. The grizzly bear (Ursus arctos) is listed as threatened by the USFWS, but it also is now extinct in Texas.

The plains spotted skunk, Spilogale putorius interrupta, and Texas kangaroo rat, Dipodomys elator, currently are under review for listing by the USFWS. Three extant taxa of Texas mammals previously have been considered candidates for listing as endangered or threatened on the federal list. They are the Davis Mountains cottontail (Sylvilagus robustus), the eastern hog-nosed skunk (Conepatus leuconotus; now considered to be conspecific with the western hog-nosed skunk), and the swift fox (Vulpes velox). Table 2 in the 1994 edition of this book listed six mammals (Mexican long-tongued bat, Choeronycteris mexicana; southeastern myotis, Myotis austroriparius; southwestern little brown myotis, Myotis occultus; northern long-eared myotis, Myotis septentrionalis; western bonneted bat, Eumops perotis; and the yellow-nosed cotton rat, Sigmodon ochrognathus), as Category 2 species in the USFWS list, meaning that the information at hand indicated it was possibly appropriate to list the species as endangered or threatened but that substantial biological data were not available to support a proposed ruling. The 1996 ESA, as amended, dissolved Category 2 and moved these taxa to the Candidate Species list, which is why they have not been included in table 2 of this new edition.

Among marine mammals, three (fin whale, Balaenoptera physalus; humpback whale, Megaptera novaeangliae; and West Indian manatee, Trichechus manatus), are listed as endangered by both the USFWS and TPWD. Two species, the killer whale, Orcinus orca, and the false killer whale, Pseudorca crassidens, are listed as threatened by TPWD and endangered by USFWS. Four species (North Atlantic right whale, Eubalaena glacialis; sei whale, Balaenoptera borealis; blue whale, Balaenoptera musculus; and sperm whale, Physeter macrocephalus), are listed as endangered by USFWS but not by TPWD. Eight species (pygmy and dwarf sperm whales, Kogia breviceps and K. sima; Cuvier's beaked whale, Ziphius cavirostris; Gervais's beaked whale, Mesoplodon europaeus; short-finned pilot whale, Globicephala macrorhynchus; pygmy killer whale, Feresa attenuata; rough-toothed dolphin, Steno bredanensis; and Atlantic spotted dolphin, Stenella frontalis), are listed as threatened by TPWD but not by USFWS.

This edition of The Mammals of Texas includes for the first time the IUCN's RedList categorization for each Texas mammal. Species considered to be critically endangered, endangered, vulnerable, and near threatened are included in table 2 along with the species listed by USFWS and TPWD. The accounts of species gives the IUCN status for each Texas mammal along with a discussion of any special circumstances regarding that species based on the work of the authors or their collaborators.

The IUCN list recognizes the Scimitar-horned oryx, Oryx dammah, as extinct in the wild. The IUCN list includes four terrestrial species (Mexican long-nosed bat, Leptonycteris nivalis; red wolf, Canis rufus; black-footed ferret, Mustela nigripes; and Davis Mountains cottontail, Sylvilagus robustus), and four marine species (North Atlantic right whale, Eubalaena glacialis; sei whale, Balaenoptera borealis; blue whale, Balaenoptera musculus; and fin whale, Balaenoptera physalus) as endangered. In the near-threatened category, the IUCN lists six native Texas species (Mexican long-tongued bat, Choeronycteris mexicana; margay, Leopardus pardalis; jaguar, Panthera onca; American bison, Bos bison; desert pocket gopher, Geomys arenarius; and banner-tailed kangaroo rat, Dipodomys spectabilis) and two nonnative exotic species (blackbuck, Antilope cervicapra, and eastern Thomson's gazelle, Eudorcas thomsonii). The IUCN list includes the Texas kangaroo rat, Dipodomys elator, and the aoudad, Ammotragus lervia, as vulnerable.

There are several species of terrestrial mammals, or populations thereof, in Texas that may well warrant protection in the future. Certainly their situation bears watching; in some cases, considerable additional data are needed to establish the facts necessary to arrive at a meaningful and biologically defensible position as to their status. Species and subspecies of concern include Elliot's short-tailed shrew, Blarina hylophaga; southeastern myotis, Myotis austroriparius; western red bat, Lasiurus blossevillii; western yellow bat, Dasypterus xanthinus; western bonneted bat, Eumops perotis; big free-tailed bat, Nyctinomops macrotis; gray-footed chipmunk, Tamias canipes; Attwater's pocket gopher, Geomys attwateri; Strecker's pocket gopher, Geomys streckeri; a subspecies of Texas pocket gopher, Geomys personatus maritimus; two subspecies of Botta's pocket gopher, Thomomys bottae limpiae and T. b. texensis; the swamp rabbit, Sylvilagus aquaticus; hooded skunk, Mephitis macroura; western spotted skunk, Spilogale gracilis; and eastern spotted skunk, Spilogale putorius. A more thorough discussion of the status of these mammals is provided in DJS's book Texas Natural History: A Century of Change.

INTRODUCTIONS OF NONINDIGENOUS SPECIES

Throughout this century a number of species have been introduced into the state, including exotic mammals (rodents and ungulates), birds, fishes, and insects. The character and composition of the fauna have changed substantially as a result of these biological invaders.

Early explorers and settlers brought Old World rats (genus Rattus) and mice (genus Mus) to the United States. The red fox (Vulpes vulpes) was introduced for sporting purposes into eastern and central Texas during the 1890s. Since 1900, however, the number of mammals introduced has increased at a staggering rate. These introduced mammals include the nutria (Myocastor coypus), feral pig (Sus scrofa), and numerous species of ungulates native to Asia and Africa. During the 1970s, a colony of feral Japanese macaques (Macaca fuscata) even became established in South Texas.

Texas has the most widespread and abundant populations of nonnative ungulates within the United States. The number of species and their populations has proliferated since their first known introduction on the King Ranch in southern Texas in the late 1920s and shortly thereafter in the Hill Country. Landowner and hunter interest in stocking exotic game has grown rapidly in recent years in response to the potential economic return to landowners, the aesthetic value of the animals, and the demand for recreational harvest opportunities for these species.

Exotic numbers began to increase rapidly in the 1950s, with the expansion of the hunting industry. Exotic surveys by the TPWD began in the 1960s. At that time, there were 13 species and about 13,000 animals. The last survey was in 1996, and it revealed 76 species and 190,000 animals. According to the Exotic Wildlife Association, there are now over 250,000 exotics in the state. The most common species (in descending order) are nilgai antelope (Boselaphus tragocamelus), axis deer (Axis axis), aoudad sheep (Ammotragus lervia), sika deer (Cervus nippon), fallow deer (Dama dama), and blackbuck (Antilope cervicapra). Among the numerous exotic ungulates, 12 species have such large populations in a free-living condition that they must now be considered permanent additions to our mammal fauna, and accounts for these species are provided in this edition. The previous edition included only six species in this category.

Ranching of exotics has become a significant source of revenue for landowners, but there is considerable concern among game biologists and mammalogists about the long-term effects of these introduced animals on native wildlife. This controversy pits the private sector, eager to diversify its agricultural base, against traditional sport hunters, conservationists, and government agencies, worried about how such activities may threaten indigenous, free-ranging wildlife, particularly ungulates and their habitat.

Some of the issues that concern conservationists and wildlife professionals about wildlife ranching and farming include disease-related interactions between commercial livestock and native animals, competitive interactions between native and exotic big game, and potential consequences of interbreeding between native and exotic big game, which could alter the genetic makeup of affected populations. There are also indications that high densities of exotic ungulates, combined with overgrazing by native deer and livestock, may severely damage rare native plants. Certainly, exotics are here to stay, but their presence challenges Texas wildlife managers to minimize habitat degradation, disease, competition, and possibly hybridization with native wildlife while at the same time retaining the economic and aesthetic attraction of such introductions. These issues emerged in the latter half of the twentieth century, but they loom even larger for the twenty-first century.

From a standpoint of regulation, exotic wildlife in Texas have the same status as domestic livestock. They are considered private property and can be used for any purpose without restrictions on seasons, bag limits, or methods of taking. Regulations governing game ranching and farming have many similarities to those of animal agriculture. Several organizations protect the interests of the exotic animal industry. The Exotic Wildlife Association, a national organization of breeders and traders in exotic ungulates, is attentive to any legislation or regulation that restricts trade or uses of exotic animals.

Several feral species have now become established in the wild in Texas and are creating conservation challenges. These include feral cats (Felis catus), which can decimate local song bird and rodent populations, and feral dogs (Canis familiaris), which can harass and kill native wildlife. Feral pigs (Sus scrofa) now exist in all 254 Texas counties, and they constitute one of the most serious ecological threats in the state. Finally, feral burros (Equus asinus) have become so numerous in the Big Bend region of the state that they are seriously impacting riparian areas, which requires their removal and often results in adverse public reaction.

The only example of a nonindigenous marine mammal is the California sea lion (Zalophus californianus), which was accidentally introduced to the Gulf by humans, although no verified sightings have been reported since 1972.

Twentieth-Century Landscape and Land Use Changes in Texas:
Impact on Wildlife Diversity

The twentieth century proved as significant for changes made by humans in the landscape—its soils, waters, atmosphere, climate, habitats, and wildlife—as for its technological advancements. The risks as we progress through the twenty-first century are not just the extinction or restriction of wildlife: there are serious economic ramifications associated with the continued loss of biological diversity. As species disappear, the human capacity to maintain and enhance agricultural, forest, and rangeland productivity decreases, and with the degradation of ecosystems, the valuable services that natural and seminatural systems provide are lost.

Essentially the problem centers on proliferating human populations and associated land conversion, which is powerfully changing the form and shape of the landscape. People now constitute a pressure on the global environment that is evident everywhere. There are no longer any unoccupied frontiers; every square centimeter of the earth's surface is affected by the activities of human beings. This results in insufficient habitat for many species or situations in which habitats are isolated in separate pieces too small or too unstable to sustain viable populations of species and thus biological diversity. The theory of biogeography reveals that species richness is a function of land area. All environmental variables being equal, the greater the area, the more species it supports. Thus, as habitats are fragmented and isolated into small islands, they lose the capacity to support wildlife diversity.

Human disturbance in Texas prior to European colonization was minimal, but the rapid spread of people across the state throughout the nineteenth and twentieth centuries greatly accelerated landscape changes. Urban development, including both urban sprawl and development of vacation homes, has had a huge impact on the landscape of Texas. The Texas population expanded from 3 million people in 1900 to more than 20 million in 2000, almost a 300% increase in one century. And, over the course of the first 14 years of the twenty-first century, it had increased by another 7 million people. Among the locations in Texas where urbanization has greatly altered the landscape, the Dallas–Ft. Worth metroplex, the Austin–San Antonio corridor, the greater Houston area, and the Juarez–El Paso area are probably the most intensive, but almost every region of the state has been severely impacted by urban development.

Population growth presents a formidable challenge to conservation because fish and wildlife resources and people share near identical needs for two critical commodities: water and land. The following major factors resulting from population growth have changed the face of Texas landscapes.

Land conversion and development. Among the most significant changes in land use are those associated with habitat conversion for development activities. Human resource use has led to a condition in which large areas of formerly continuous landscapes have become increasingly fragmented and isolated. Habitat fragmentation is rapidly becoming the most serious threat to landscape integrity in Texas today.

Misuse of water. Of all the water resources in Texas, rivers and streams are by far the most seriously threatened. There are 15 major river systems and more than 11,000 named streams in the state, but very few of them are free-flowing today. Many aquatic habitats in Texas have been altered and fragmented by dams and water diversions. Adequate stream flows and good water quality are essential to the health of our watersheds and the ecosystems they support.

Suppression of fire. Beginning in the nineteenth century and continuing throughout the next, fire suppression has had a huge impact on the state's grassland, woodland, and forest habitats. Historic wildland fires were frequent, naturally occurring, and of low intensity. Since the early 1900s, fire suppression has allowed the development of ladder fuels and the accumulation of heavy fuel loads, resulting in more catastrophic fires.

Invasion of nonnative plants. By the end of the twentieth century, alien plants had become common all over the state. In particular, the salt cedar, or tamarix, has inflicted damage to native landscapes and habitats. It is a vigorous invader of moist pastures, rangelands, and riparian habitats and has spread to almost every river, stream, creek, and wash over much of the state. Other destructive alien plants include Russian olive and Russian knapweed, which have invaded much of our rangelands.

Loss of wetland-like habitats. Large-scale loss and degradation of riparian landscapes throughout the state have resulted from the construction of impoundments; overgrazing by livestock, which has destabilized vegetation and resulted in arroyo cutting and gullying of the landscape; and the introduction of alien plants such as salt cedar and Russian olive. All of these factors have negatively affected fish and wildlife habitat.

Encroachment of brush. Since the turn of the twentieth century, brush and cacti have continued to cover many areas of the state that were formerly prairie or grassland. The spread of species such as mesquite, cedar, cholla, and prickly pear can be attributed primarily to overgrazing and the suppression of wildfires that so often swept over the state in the past. The two most obvious culprits contributing to the increase in woody plants have been mesquite and juniper.

Grazing of livestock. Livestock grazing, together with fire suppression, both interacting with fluctuations in climate cycles, has had a major impact on land cover in Texas. The extremely high historical stocking rates and concomitant overgrazing have led to significant alterations in the species composition of vegetation across all ecoregions in the state.

Resource extraction activities. Habitat disturbances associated with logging, mining, oil and gas development, groundwater depletion, and hydropower occur throughout Texas, and they have impacted ecosystems in localized areas. Groundwater levels in Texas have dropped considerably due to pumping for agricultural crop irrigation and urban needs, causing significant wetland habitats to dry out. Pollution factors such as agricultural chemicals, livestock and dairy groundwater contamination, and solid waste also have negatively affected habitats.

Many of these factors are closely linked in cause and effect across spatial and temporal scales, and they have had an accumulative effect on our fauna and flora. For example, over the past century species composition and structure of Texas's forest and woodlands have been altered by the combined effects of commercial logging, fire suppression, and improper grazing practices. These changes have virtually eliminated fire as an ecological process and have had a negative overall impact on both forest and prairie ecosystems and their wildlife resources. Management of water will be the single most critical conservation issue in Texas in the twenty-first century. Water is the limiting factor for all aquatic life, plants, and wildlife as well as people. Global warming or climatic change in the form of prolonged droughts will exacerbate these challenges.

Impact of Climate Change

The natural patterns of mammalian diversity could be altered drastically in the twenty-first century if scenarios of climate change come to be. Under general climate change models, which predict changes in global climate due to increased levels of atmospheric carbon dioxide, environmental variables in Texas could change rapidly and, in turn, change the distribution and diversity of mammals. Changes in temperature and rainfall patterns will cause changes in the distribution of plant communities, which in turn would affect the distribution of mammals throughout the landscape.

There are a number of ways that climate change can impact wildlife. Temperature increases and changes in precipitation can directly affect species depending on their physiology and tolerance of environmental change. Climate change also can alter a species' food supply or its reproductive timing, indirectly affecting its fitness. Most mammals will not be able to avoid the effects of climate change, with both positive and negative effects possible. Mammals generally utilize a variety of often disjunct resources. They need places to hide, eat, drink, and breed, and in many cases these places are distinct and may change seasonally. Thus, there are many opportunities for climate change to disrupt mammalian life histories. Most mammals also are highly mobile and, compared with perennial plants, have relatively short (generally <20 years) life spans. Thus, if climates become unsuitable, mammalian response can be expected to be rapid.

Guy Cameron, formerly of the University of Houston, and his students used models of climate–vegetation association to predict mammalian distributions under current conditions and under two future climates that would occur if carbon dioxide levels double, as has been predicted. Both future climates were warmer, but one was wetter and the other drier than current conditions. Under both future climatic conditions, all temperate vegetation in Texas would be lost. Under drier conditions, steppe and scrub habitats would appear in the state; under wetter conditions, subtropical habitats would appear.

In general, rodents are predicted to be the most adaptable group of mammals to global climate change. Cameron's analysis predicts extinction for only two rodent species, the Mogollon vole (Microtus mogollonensis) and Coues's rice rat (Oryzomys couesi), both of which have restricted ranges in the state. Four rodent species are predicted to show large increases in geographic distributions, including the gray-footed chipmunk (Tamias canipes), the brush deermouse (Peromyscus boylii), and the Mexican woodrat (Neotoma mexicana) under the drier climate, and those plus the northern rock deermouse (Peromyscus nasutus) under the wetter climate. Half of rodent species ranges are predicted to decrease under drier climates and 63% are predicted to decrease under wetter climates. For both insectivores and lagomorphs, no species are predicted to go extinct in the state, but species ranges are predicted to contract under both drier and wetter conditions and species diversity is predicted to decrease in the southern part of the state.

Ranges of bats dependent on fixed roosts such as caves and rock crevices are predicted to decrease substantially under wetter climatic conditions, but a few are predicted to expand under the drier model. Conversely, tree-roosting and generalist bat ranges are predicted to increase under both climatic scenarios. Under both future climates, species richness is predicted to decrease in West Texas because of the loss of cavity-roosting bats but to increase in southern and central Texas with the expansion of tree-roosting bats. Again, no species are predicted to go extinct under new climatic conditions.

Analyses of mammal communities as a whole in Texas reveal that individual species are predicted to respond differently to climate change. This suggests that mammal communities do not shift together as a whole, but each species shifts independently of other species, which will result in new associations of mammals and different mammal community structure as climatic conditions change. This also may be true of plant species. If so, vegetation communities may not shift as a unit, and the result will be new kinds of plant communities. These observations are consistent with the observations made about the influence of environmental variables on the current distribution of mammals.

Bats are a group of Texas mammals that may already be responding to climate change because of their sensitivity to temperature and precipitation variations. Just in the past two decades we have seen evidence of some bat species substantially expanding their geographic ranges in Texas. Two Mexican species (Mexican long-tongued bat, Choeronycteris mexicana, and the western yellow bat, Dasypterus xanthinus) have moved northward into areas in the state where they were not previously known. Likewise, bats previously common in eastern Texas (American perimyotis, Perimyotis subflavus; evening bat, Nycticeius humeralis; and Seminole bat, Lasiurus seminolus) have recently been documented from places in the far western part of the state. These bats were all captured in areas where bat specialists had previously collected for decades, so it is not likely the bats would have been overlooked if they had occurred there in the past.

Changes in life history strategies also may be developing in some bats. Ken Wilkins and Anica Debelica of Baylor University studied reproductive patterns in three relatively common species (big brown bat, Eptesicus fuscus; American perimyotis, Perimyotis subflavus; and Seminole bat, Lasiurus seminolus) in southeastern Texas and found a shift in reproductive pattern from synchronous monoestry (common in temperate bat species) to extended seasonal monoestry (common in tropical bat species). These two bat biologists postulated that earlier parturition in these bats could be driven by a response to global warming and predicted the same pattern may become evident in other species that occur along the coastal plains of the southeastern United States.

Conservation Strategies

It seems inevitable that the twenty-first century will be as different from the twentieth century as the twentieth century was from the nineteenth, perhaps more so given the accelerating pace of change in lifestyle and technology. The next hundred years is likely to decide the future of wildlife in Texas and other states. Decisions will be made, directly or indirectly, as to how much and what kind of nature survives. Conservation pressures in the next century will come from a variety of sources. Habitat loss, fragmentation, and degradation are the most important causes of wildlife decline, but overharvesting and poaching, trade in wild animal products, introduction of exotic species, pollution from pesticides and herbicides, and other causes also take a significant toll. Global warming or climate change could exacerbate the loss and degradation of biodiversity by increasing the rate of species extinction, changing population sizes and species distributions, modifying the composition of habitats and ecosystems, and altering the geographic extent of species, habitats, and ecosystems.

A recent study conducted by scientists associated with the United Nations Environment Program has estimated that almost a quarter of the world's mammals, approximately 1,130 species, could face extinction by the end of the twenty-first century. The loss of habitats by human encroachment is largely responsible for the predicament faced by 83% of the threatened mammals listed in the report. The report concludes that all the factors that have led to the extinction of species in recent decades continue to operate with "ever-increasing" intensity. Texas has a great treasure in its mammalian fauna, which provides our citizens with important recreational, commercial, aesthetic, and scientific values. The state is home to over 20% of the nation's total deer population, over 75% of the carnivore species, and all but 10 species of bats that occur in the United States. The question is whether these resources can be sustained in the future. For that to happen, we must employ several conservation strategies. It has become clear in most cases that single approaches will not work successfully to conserve wildlife diversity. We must build long-range thinking and planning into conservation, and we must find ways for diverse groups, including state and federal agencies, academic institutions, private landowners and organizations, and public groups to network and explore new collaborative ventures that bring separate approaches together in a complementary way. The challenge is daunting. We face a monumental task, far beyond our existing abilities, but now is the time to look ahead, coordinate and plan, before our options are further narrowed. There are hundreds of resource-based natural areas in Texas that potentially could serve as biological reserves for the protection of species and the supporting environment. They include national parks, forests, preserves, and recreation areas; national wildlife refuges; state wildlife management areas; state parks, natural areas, and historic sites; and local parks (including cities, counties, and river authorities). More than 1.6 million hectares (4 million acres) of land are contained in these units, which are distributed throughout the state and provide habitat for most Texas mammals. In addition, several private conservation organizations, most notably the Nature Conservancy of Texas, have land acquisition programs and private landowner partnerships for conservation. With 37 Texas nature preserves and conservation properties and more than 100 private landowner partnerships, the Nature Conservancy has to date protected over 355,315 ha (878,000 acres) in Texas.

Although protected areas play a key role in the preservation of natural diversity, their ability to preserve our mammalian fauna is limited and sometimes overestimated. Their capacity for preservation is restricted by a number of internal and external factors. First, the parks and preserves of Texas are scattered throughout the state, but the geographical distribution is far from proportional. Thus, many of the natural areas in Texas, such as native grasslands and prairies, are poorly represented. Second, most protected areas are too small and widely scattered to preserve biological diversity effectively. A 1987 publication in the scientific journal Nature concluded that the 14 largest national parks in western North America were too small to retain an intact mammalian fauna. No protected area in Texas is as large as the smallest of the 14 parks used in that study. Thus, a major goal of conservation must be to expand the number of protected areas to include a cross section of all major ecosystems in the state and to link them via conservation corridors so they are more effective. Protected areas alone, however, will not be sufficient to conserve mammalian diversity in Texas. To be effective in the long term, conservation strategies must consider the needs of local residents to maintain or enhance their quality of life. For that reason, conservation-based rural development is indispensable to any successful conservation strategy in Texas. With about 94% of the state in private land, it will not be possible to conserve mammalian diversity in Texas without the support and participation of landowners. In order to retain the stability and diversity of this habitat, it must be managed and utilized by landowners in an economically and ecologically viable manner. A system of responsible wildlife management, sportsmanship, and land ethics must be developed. Aldo Leopold, the father of American wildlife management, recognized this more than 80 years ago when he wrote about the need to recognize the landowner as the custodian of public game on all private lands and to compensate landowners for putting land in productive condition by making game management a partnership enterprise so that the landowner, the sport hunter, and the public each contribute appropriate services as well as deriving appropriate rewards.

A basic weakness in a conservation system based wholly on economic motives is that most species of a land community have no economic value. Without a land ethic and a stewardship concern for the diversity and integrity of the land, landowners will favor those management practices that make the most money without a consideration of the whole biotic system. Landowner rights and wildlife management, including the protection of endangered species, can and must be integrated to achieve effective conservation of mammals in Texas. We must learn to manage the landscape for sustained local diversity, maintenance of ecosystem function, and renewable yields of natural resources for economic development.

Texas has one of the most aggressive landowner assistance programs in the nation. Several state and federal agencies, as well as private organizations, offer incentive programs that provide technical or cost-share assistance to private landowners for voluntarily enrolling environmentally sensitive land or wildlife habitat in conservation programs to protect or enhance natural resources. Such programs might include anything from advice about cross fencing to habitat restoration for endangered species. The TPWD has been particularly aggressive in fostering landowner assistance programs, with nearly 12 million hectares (30 million acres) of private land being managed under individually tailored wildlife management plans designed and shepherded by state employees. Other tools that are gaining popularity among landowners as we enter the twenty-first century include land trusts, conservation easements, and property tax benefits for wildlife management. Collectively these various programs provide some sort of wildlife management to another 1.6 million hectares (4 million acres) of land in Texas. Given that agriculture is the prevalent land use on approximately 55 million hectares (136 million acres) of Texas lands, representing about 81% of the state's total land area, almost 25% of the state's available acreage is under some form of wildlife management. As we look to the future, there is a need for even more programs designed to encourage private landowners to practice conservation.

We also must improve our biological knowledge about mammals. We know precious little of the life history of most mammals in Texas. In fact, for many species our knowledge is insufficient even to assess their status accurately. Decisions as to whether a species is threatened, rare, or endangered are often based entirely on biological guesswork without proper knowledge of the population dynamics, reproduction, food habits, or behavior of the species considered. Future research efforts, whether they involve biologists working for state and federal agencies or scientists associated with academic institutions, should focus on correcting those omissions.

Conserving wildlife, which recognizes neither ownership nor boundaries, calls for good science, first-rate technology, excellent management, and a broad constituency willing to make some concessions to save it. Whether we act, and how, will depend on factors such as politics, education, socioeconomics, recreation interests, and planning capabilities. Broad-based conservation education programs, designed to diffuse conservation information to the public, must become a priority. Without an understanding of the need for action, and without a commitment to that action, citizens will not contribute to the effort, nor will they cooperate with those so engaged. People must be educated to understand what the continuation—or destruction—of wildlife means to their future and that of their descendants, and they must be persuaded to act on their resulting concern in ways respectful to the diversity of wildlife and to their own cultural values.

Wildlife management and conservation in Texas have reached a crossroads. The state's burgeoning population, now approaching 28 million people, is altering wildlife habitat at unprecedented rates because of human influence. Efficient and effective management has become more crucial than ever for the future of wildlife habitats, but to be successful it must be accomplished by incorporating all stakeholders into the process. Unfortunately, the human side of wildlife management has not received as much attention as wildlife species or their habitats, even though it is so necessary for effective management. Wildlife in Texas belongs to the public, which must be considered in management decisions, yet much of the public's access to these resources is controlled by private landowners. Simply addressing animals and their habitats on private lands will not address the complexity of wildlife management in the twenty-first century, especially with increasing human demands for landscape use. Wildlife habitat is decreasing, and human use of those lands is creating serious challenges. In the future, we must have leaders in wildlife management and conservation who are able to understand both the biology of wildlife species and how landscapes can be managed to ensure their survival and long-term viability.

History of Mammalogy in Texas

During the time that Vernon Bailey (fig. 6a) and the federal agents worked in Texas, there were no professionally trained mammalogists living in the state. A number of private citizens called themselves amateur naturalists, and they collaborated with the federal agents. The person who was the closest to being an expert was probably Henry P. Attwater (fig. 6b) from San Antonio. Mr. Attwater made extensive collections in the regions about San Antonio and Aransas Pass and discovered a number of new forms (including Attwater's prairie chicken) that were described by Dr. J. A. Allen in various bulletins of the American Museum of Natural History.

Vernon Bailey's 1905 publication (fig. 6c) was the first comprehensive study of mammals in the state and set the stage for further studies of their distribution, taxonomy, and natural history. In 1907, Edgar Alexander Mearns, a medical doctor assigned to the US Army, published an account of the mammals of the Mexican boundary of the United States, which included considerable detail about Texas mammals along the border. An updated checklist of mammals was published in 1926 by John K. Strecker (fig. 6d), curator of the museum at Baylor University, but the progress of mammalogy in Texas was slow for the first portion of the twentieth century. It was not until the decade of the Great Depression that the science started in earnest again. During the latter half of the twentieth century, the science of mammalogy exploded in Texas as a major field of research and education. A detailed account of this history, including the major events and the many individuals who made significant contributions to it, is beyond the scope of this book, but highlights of the subject can be found in several of the sources listed in appendix 3.

Among the most significant developments, the following are especially noteworthy.

• In 1935 the Cooperative Wildlife Research Unit at Texas A&M was established under the leadership of Walter P. Taylor (fig. 6e); it was the first organized research unit to study wildlife management in the state.

• In 1937 the Department of Fish and Game (now the Department of Wildlife and Fisheries Sciences) was established at Texas A&M; under the direction of William B. Davis (fig. 6f), it began to train graduate and undergraduate students in mammalogy and started the Texas Cooperative Wildlife Collections, the first major collection of mammals in the state. In 1971, DJS became associated with this program and continued to work with Davis until DJS left to join Texas Tech University in 1996.

 Mammalogy in Texas

Figure 6. Historical contributors and contributions to the study of mammalogy in Texas. Shown are (clockwise from top left) Vernon Bailey (photo courtesy of the Library of Congress); Henry P. Attwater (photo courtesy of the Library of Congress); John K. Strecker (photo courtesy of Baylor University, Mayborn Museum Complex); Walter P. Taylor (photo courtesy of the US Geological Survey–PWRC, Biological Survey files); and William B. Davis (photo courtesy of Texas A&M University, Department of Wildlife and Fisheries Sciences); and frontispiece of the Biological Survey of Texas, 1905.

• During the 1940s and 1950s other mammalogy programs were developed in the state, including at the University of Texas at Austin (W. Frank Blair, fig. 7a), Midwestern State University (Walter Dalquest, fig. 7b), and Stephen F. Austin University (Howard McCarley, fig. 7c).

• In 1947 The Mammals of Texas by Walter Taylor and William B. Davis was published; it was the first comprehensive survey of Texas mammals since Bailey's 1905 publication. The publication was revised three times by William B. Davis (1960, 1966, and 1974), once by Davis and DJS (1994), and again by DJS in 2004.

• In 1971 the Museum and the Natural Science Research Laboratory at Texas Tech University was established. Texas Tech has now become the leading center for the study of mammals in the state, and it houses the state's largest scientific collection of mammals. Occasional Papers and Special Publications of the Museum, both produced at Texas Tech, have become the leading publication outlets for mammalian natural history studies. As of 2015, more than 340 scientific papers on mammalogy have been published in these two outlets. The leaders in the establishment of this program were J. Knox Jones Jr. (fig. 7d), Robert J. Baker, Clyde Jones, Robert L. Packard (fig. 7f), Dilford Carter, and Robert D. Bradley.

Additional Historical Contributors

Figure 7. Additional historical contributors, all now deceased, to the study of mammalogy in Texas. Shown are (top row, left to right) W. Frank Blair (photo courtesy of the Chihuahuan Desert Research Institute Nature Center, Fort Davis, Texas); Walter Dalquest (photo courtesy of Midwestern State University, 1984); and Howard McCarley (photo courtesy of Southwestern Association of Naturalists archives); and (bottom row, left to right) J. Knox Jones Jr. (photo courtesy of Department of Biological Sciences, Texas Tech University); Clyde Jones (photo by Mary Ann Jones); and Robert L. Packard (photo courtesy of Department of Biological Sciences, Texas Tech University).

• In 1990 the Texas Cooperative Fish and Wildlife Research Unit was reopened at Texas Tech University, and in 1993 this lab affiliated with the nationwide Gap Analysis Program. Gap analysis was begun by the USFWS in 1989 as a protocol to identify geographic areas with important wildlife and habitat attributes in need of protection. Using geographic information system technology, a statewide database has been developed that represents vegetation communities, terrestrial vertebrate distributions, and boundaries of federal and state conservation areas. The Gap Analysis Program is intended to provide resource managers with the most advanced and comprehensive tools to prioritize land use and conservation decisions.

• At both the undergraduate and graduate levels, wildlife and fisheries programs as well as field biology curricula at universities in Texas and the hiring of professionally trained naturalists to teach and establish research programs has been institutionalized. With the explosion of trained scientific talent, including in both terrestrial and aquatic environments, academic institutions all across the state began to hire mammalogists and make the subject an important area of research and education. Almost every university in Texas, both public and private, has at one time or another employed a mammalogist and offered an academic course on the subject. More recently, mammalogists have been employed by state and federal governmental agencies responsible for natural resource management in the state (e.g., the TPWD, the USFWS, and the National Park Service) as well as many nongovernmental organizations (e.g., the Nature Conservancy of Texas and Bat Conservation International).

• The Marine Mammal Stranding Network and the research and graduate education program at Texas A&M University at Galveston were established. This is one of the largest academic research programs in the world devoted to the study of whales, dolphins, and manatees. The Marine Mammal Stranding Network, established in 1981, has collected information on several thousand marine mammals that have washed ashore on Texas beaches during the last four decades. The key people who helped establish the marine mammal program in Galveston were DJS, William Merrill, Bernd Würsig, Bill Evans, Randy Davis, and Graham Worthy.

The literature about mammalogy in Texas has grown exponentially throughout the last century. Students and professionals working in the state have published several thousand scientific papers about Texas mammals. A comprehensive list of these papers was compiled in 1962, and the list was updated every subsequent decade until the 1990s. Now the proliferation of published information is so extensive that it is virtually impossible to keep up with all of the publications. The twentieth century also witnessed the growth of collections of mammals in Texas. The major collections are located at Texas Tech University and Texas A&M University. The collection at Texas Tech will soon reach 125,000 specimens, including nearly 100,000 specimens with frozen tissues available for genetic study. The Texas Cooperative Wildlife Collections at Texas A&M has over 63,000 specimens, many with genetic tissues. Collections that house almost 20,000 specimens are housed at Midwestern State University and Angelo State University.

The crowning achievement in the growth of mammalogy in Texas was the establishment in 1981 of a separate scientific society, the Texas Society of Mammalogists. The late Robert L. Packard of Texas Tech University was the lead organizer of the society. Texas is the only state in the United States with a state scientific society devoted to mammalogy, and there are more professional mammalogists living in Texas than in any other state in the United States.

The mission of the Texas Society of Mammalogists, as stated in its constitution, is to "promote the study of mammals, living and fossil" in Texas. Beginning in 1983, the society has met in February of every year at the site of Texas Tech University's Junction Campus in Kimble County. Mammalogists and students from throughout the state convene and present papers and hold discussions about the biology and conservation of Texas mammals. The membership of the Texas Society of Mammalogists now numbers approximately 240.

Clearly, Bailey and the federal agents planted a seed that would grow into a major scientific field of study. They probably had no idea this would happen, but it is almost certain they would be pleased with the outcome. The scope of the science of mammalogy and the scientific talent available in the state will be crucial to our ability to manage and conserve mammalian species and communities wisely in the twenty-first century.

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From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.

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