Texas Tech University

Order Chiroptera

BATS

Chiroptera, meaning hand wing, alludes to the great elongation of the fingers that support the flying membrane.  Among mammals, bats are unique in that they have true powers of flight; other mammals, such as flying squirrels, can only volplane, or glide, always from a higher to a lower elevation.  Bats as a group are crepuscular or nocturnal; their eyes are small and inefficient, although their ears are usually well developed.  Bats use high-frequency, ultrasonic sounds (generally >20 kilohertz, outside our hearing range) to navigate and avoid obstacles and capture prey in the dark.  The ability to produce ultrasonic pulses and to interpret the echoes rebounding from objects in their path is called echolocation. 

In the temperate regions, the young are born in late spring; in the tropics, there appears to be no definite breeding season -- young bats may be found in every month of the year.  Most bats feed on insects, but some kinds feed regularly on fruits, nectar, or fish, and some, the vampire bats, are peculiarly adapted to feed on blood. 

Bats live nearly everywhere on earth with the exception of the polar regions, highest mountains, and some remote islands.  Their diversity and abundance, however, are greatest in tropical regions, declining steadily north and south of the equator.  Bats are common in the United States and can be found easily in most regions, although they are most abundant in the Southwest.  Thirty-three of the 43 species of bats in the United States occur in Texas, the richest variety of bat species found in any state in the country. 

Bats occur in all the major ecological regions of Texas, but the Big Bend region of the Trans-Pecos, with its topographic pattern of high mountains and desert lowlands, supports more kinds of bats (20 species) than any other part of Texas.  Several extremely rare or unusual bats occur in this region, and they are more abundant here than anywhere else in the country.  The Edwards Plateau also contains a high diversity of bats, primarily cavern-dwelling species that inhabit the numerous caves of the region, often in staggering numbers.  Caves are excellent roosting and hibernation sites for bats, and they play a prominent role in the distribution of many bats in our state.  Bat species diversity and numbers are lower in the northern, eastern, and southern portions of the state, where topographic heterogeneity is low and caves are uncommon. 

In many parts of North America, bats either migrate or hibernate in winter.  If they migrate, their distributions in winter and summer are often very different.  In parts of Texas where the climate is mild, bats may not migrate or hibernate if weather conditions are such that a sufficient and suitable food supply is available year-round.  In general, however, there is a tendency for most species of bats in our state either to move from one region to another or to move out of the state altogether during the months of November through March. 

As a group, bats have the most diverse food habits of any order of mammals.  Although there are no truly herbivorous (plant-eating) bats, the order Chiroptera includes members that specialize in almost every other diet conceivable.  Some bats feed exclusively upon insects and other arthropods (insectivory), flesh (carnivory), fish (piscivory), fruit and flowers (frugivory), pollen and nectar (nectarivory), or blood (sanguivory), and some bats eat a variety of food items (omnivory).  The bats in Texas are predominantly insectivores (30 species), but two nectarivores also occur here, and one sanguivore has been documented by a single specimen in the state. 

Drastic reductions in bat populations have been reported in recent years not only in the United States but worldwide as well.  Several species of bats are already extinct, and others are near extinction.  As a group, bats are exceptionally vulnerable to extinction because they typically rear only one young per year and hence are slow to recover from major population declines.  In addition, many species form large aggregations, which are vulnerable to mass destruction. 

The causes of declining bat populations are not always evident, and many possible factors may be responsible.  Global climate change is already indirectly impacting bat populations around the world and in Texas.  In addition, major adverse effects, including the destruction of habitat, outright extermination, vandalism at roost sites, excessive disturbance at roosts and maternity colonies, pesticide poisoning, and use of other chemical toxins, have been brought about by humans.  Natural factors also can play a role in declining bat populations, the most serious of which is white-nose syndrome, a fungal infection that is devastating bat populations in the eastern United States and is rapidly moving west. 

White-nose syndrome is a recent disease caused by a fungal infection, Pseudogymnoascus destructans (formerly Geomyces destructans), that concentrates on the nostrils of bats.  The fungus appears to occur in colder caves and tolerates a fairly narrow range (4°C-15°C) of cave conditions.  Although respiration is impacted, the major effect of the disease is that it causes bats to exit the torpor condition prematurely.  Often, infected bats arouse too early in the spring or late winter and ultimately starve to death due to the absence of insect prey.  

White-nose syndrome was first documented in the northeastern United States in 2007.  Since then the disease has spread westward and southward to Missouri, Oklahoma, and Iowa, although it appears that the movement of the disease may be slowing.  In some cases, a mortality rate of 90% has been recorded, and some predictions indicate that overall bat numbers may suffer major declines and extinction may occur for some cave-dwelling species.  Although white-nose syndrome has not been documented in Texas, it may only be a matter of time before it impacts our native species.  Caution should be exercised by professional and amateur spelunkers and bat biologists to avoid the inadvertent introduction of P. destructans into an uninfected cave or roost site.  Several conservation groups and state agencies provide detailed instructions relative to decontamination protocols when exiting potentially contaminated caves. 

Another major concern for Texas bats is the erection of wind turbines for electricity production.  Over the last 10 years, wind energy has increased dramatically in Texas, especially in the western portions of the state, where wind farms may contain anywhere from 10 to 1,000 wind turbines.  In some regions of the United States, wind turbines have been implicated in the deaths of up to 600,000 bats per year.  Most often, bats are killed when they approach too closely to the vortex caused by the rotating blades.  The changes in air pressure cause the bat's lungs to explode (called barotrauma).  The overall impact on bat populations is mixed, with tree bats being the most dramatically affected.  It appears that tree-roosting bats are somehow attracted to the wind towers, either mistaking them for roosting sites or perhaps being attracted by the sound of the motor or rotating blades.  At wind farms in West Texas, where tree bats are scarce, the impact appears to be minimal.  It may be that wind farms located in areas devoid of trees and tree-roosting bats may offer a sound compromise between conservation and green energy. 

Rabies is a disease that is known to be transmitted by bats to people in Texas, although fears of acquiring it from bats have been often grossly exaggerated.  To evaluate the prevalence of rabies in bats, mammalogists in that state have for several decades worked with staff at the Texas Department of Public Safety (DSHS) to identify those bats submitted to the agency by the public for rabies testing.  These data have contributed to our knowledge about the distribution of many species as well as furnishing information on the prevalence of bat rabies in Texas.  Of the 33 species of bats that occur in Texas, 27 have been documented with rabies somewhere in their range, although not necessarily in Texas.  The DSHS bat records are included on the distribution maps for each of the Texas species of bats to complement the records from museum specimen collections and from the published literature. 

Texas has a long and interesting history of involvement with bat conservation efforts.  Efforts to construct artificial structures for attracting bats were pioneered in the state.  In the 1910s and 1920s, Dr. Charles A. R. Campbell of San Antonio promoted construction of numerous bat towers, structures that looked like church belfries on stilts (fig. 37).  As the chief public health physician for the city of San Antonio, one of Campbell's jobs was to maintain quarantine camps.  He theorized that bats would control mosquitoes, which would reduce malaria, still a significant disease in Texas at that time.  He also promoted guano as fertilizer; in one year (1917) he recovered 1,359 kg (2,996 lb.) of guano from a tower at Mitchell's Lake, a sewage lake near San Antonio.  Furthermore, it was Campbell who influenced the State Board of Health and the state legislature to pass legislation in 1917 protecting bats.  On 9 March 1917 the Texas legislature passed House Bill 40, "An act making it a misdemeanor to kill or in any manner injure the winged quadraped known as the common bat," with a $5-$15 fine for anyone found guilty of violating the law. 

Bat Roost

Dr. Campbell received a patent in 1914 for the design of his bat towers (US Patent No. 1,083,318, issued January 6, 1914; Patent Office Gazette 198: 20-21), and in 1919 the state legislature passed a resolution nominating him for the Nobel Prize.  In 1925, he published a book, Bats, Mosquitoes, and Dollars, in which he claimed that the bat guano from his towers contained mosquito fragments, and he had many people attest in writing to a dramatic reduction in mosquitoes at Mitchell's Lake after installing a bat tower in 1911.  He also urged communities to construct bat towers (estimated to cost from $2,500 to $3,500) for controlling mosquitoes and harvesting guano. 

Professional mammalogists were skeptical of the accuracy of Campbell's statements and conclusions.  In 1919 Tracy Storer, a well-known mammalogist working for the US Biological Survey, visited one of the bat roosts near San Antonio and obtained some guano samples, which he had analyzed by entomology experts.  None of the samples contained the remains of mosquitoes, and Campbell's assertions lost credibility in scientific circles. 

Probably the most useful product of Campbell's work was the development of a generally benign attitude about bats among the public.  According to cave biologist William R. Elliot, that attitude changed in the 1950s as a result of a series of rabies scares around the state.  As a result, the legislature unanimously rescinded the bat protection law (1957), and the public attitude toward bats hardened.  Almost all of Campbell's bat towers were eventually torn down. 

Recently, a Texas landowner and conservationist by the name of J. David Bamberger, who owns a 2,225 ha (5,500 acre) ranch in the Hill Country near Johnson City, constructed an artificial bat cave in an attempt to provide artificial habitat for bats.  His "chiroptorium" was built in 1997-1998 at a cost of about $170,000.  The cave covers 279 m2 (3,000 ft.2) and its walls offer roughly 743 m2 (8,000 ft.2) of roosting space.  Now that it has been covered with soil and native grasses, the cave blends nicely into the natural landscape of the ranch.

For the first few years after construction, bats came and went from the chiroptorium.  Most seemed to be travelers; they would stay for a few days or sometimes a few months.  Then in the summer of 2002, several hundred bats came to the cave, and on 5 August 2003, Mr. Bamberger witnessed a huge emergence at the cave entrance lasting many minutes.  In June 2004, Dr. Gary McCracken, a noted bat biologist from the University of Tennessee, visited the site.  After an evening emergence of Brazilian free-tailed bats (Tadarida brasiliensis), the scientist and several staff went into the interior of the cave and discovered that this colony had become a maternal colony, harboring females and their young.  The biologists estimated that about a 1 m(10.8 ft.2) on the ceiling of the back dome was covered in bat pups, which would be about 5,000 babies.  In May 2008, bat biologists from Boston University, using infrared video photography, determined that there were 116,000 bats in the cave.  So, it can now be said with certainty that Bamberger's "project" is officially a success, and it is predicted that more free-tailed bats will occupy the artificial cave in the future.  The cave myotis (Myotis velifer) has also been documented in the cave in very small numbers, but it has been documented to breed there. 

Owing to its geological complexity, Texas has many caves, and they are especially important for the conservation of bats, supporting large populations of bats throughout the year.  Mining, human disturbance, and pollution have been and continue to be the biggest threats to bats that live in Texas caves.  Given the diversity and large population size of bats in Texas, and especially in consideration of their overall ecological and economic importance in the state, it is crucial that we develop a far better understanding of their ecological requirements in order to develop appropriate conservation actions and management plans. 

In 2012, Loren Ammerman, Christine Hice, and DJS published a revision of DJS's 1991 book, The Bats of Texas, which provides greater detail about the natural history, distribution, taxonomy, and conservation of Texas bats.  The interested reader should refer to it for more information about bats living in Texas. 

 

KEY TO THE BATS OF TEXAS

1. Distinct, upwardly and freely projecting, triangular nose leaf at end of elongated snout .......................................................................... 2

Nose leaf absent, indistinct, or modified as lateral ridges or low mound-like structure; snout normal ............................................................... 3

2. Tail evident, projecting about 10 mm from doral side of interfemoral membrane; distance from eye to nose about twice distance from eye to ear; forearm <48 mm.  Choeronycteris mexicana (Mexican long-tongued bat).

Tail not evident; eye about midway between nose and ear; forearm >48 mm.  Leptonycteris nivalis (Mexican long-nosed bat).

3. Thumb >10 mm; hair straight, lying smoothly, glossy tipped.  Diphylla ecuadata (hairy-legged vampire bat).

Thumb <10 mm; hair slightly woolly, pelage lax, not usually lying smoothly, not glossy tipped .............................................................................. 4

4. Prominent grooves and flaps on chin; tail protruding from dorsal surface of interfemoral membrane.  Mormoops megalophylla (ghost-faced bat).

No notable grooves or flaps on chin; lumps above nose or wrinkled lips possible, most faces lacking even these characteristics; tail extending to or beyond the edge of the interfemoral membrane ............................................... 5

5. Tail extending conspicuously beyond free edge of interfemoral membrane .............................. 6

Tail extending to free edge of interfemoral membrane ...................... 9

6. Forearm >70 mm; upper lips without deep vertical grooves.  Eumops perotis (western bonneted bat). 

Forearm <70 mm; upper lips with deep vertical grooves .................. 7

7. Forearm <52 mm ................................................................... 8

Forearm >52 mm (58-64).  Nyctinomops macrotis (big free-tailed bat).

8. Ears not united at base; second phalanx of fourth finger >5 mm.  Tadarida brasiliensis (Brazilian free-tailed bat).

Ears joined at base; second phalanx of fourth finger <5 mm.  Nyctinomops femorosaccus (pocketed free-tailed bat).

9. Ears disproportionately large, >25 mm from notch to tip .............. 10

Ears of normal size, <25 mm from notch to tip ............................... 13

10. Color black with three large white spots on back, one just behind each shoulder, the other at the base of the tail.  Euderma maculatum (spotted bat).

Color variable but not black; no white spots on back ........................ 11

11. Dorsal color pale yellow; no distinctive glands evident on each side of the nose.  Antrozous pallidus (pallid bat).

Dorsal color light brown to gray; distinctive glands (large bumps) evident on each side of the nose ................................................................... 12

12. Hairs on belly with white tips; strong contrast in color between the basal portions and tips of hairs on both back and belly; presence of long hairs projecting beyond the toes; known from eastern one-third of state.  Corynorhinus rafinesquii (Rafinesque's big-eared bat).

Hairs on belly with pinkish-buff tips; little contrast in color between basal portions and tips of hairs on both back and belly; absence of long hairs projecting beyond the toes; known from western half of state.  Corynorhinus townsendii (Townsend's big-eared bat).

13. At least the anterior half of the dorsal surface of the interfemoral membrane well furred .................................................................................. 14

Dorsal surface of interfemoral membrane naked, scantily haired, or at most lightly furred on the anterior third .................................................. 21

14. Color of hair black, with many of the hairs distinctly silver tipped.  Lasionycteris noctivagans (silver-haired bat).

Color various but never uniformly black .......................................... 15

15. Color yellowish ...................................................................... 16

Color reddish, brownish, or grayish (not yellowish) .......................... 18

16. Total length >120 mm.  Dasypterus intermedius (northern yellow bat).

Total length <120 mm ................................................................. 17

17. Hairs of dorsal uropatagium bright yellow with little darkness.  Dasypterus xanthinus (western yellow bat).

Hairs of dorsal uropatagium lacking bright yellow sheen and having a distinct smoky appearance.  Dasypterus ega (southern yellow bat).

18. Forearm >45 mm; color wood brown heavily frosted with white.  Aeorestes cinereus (hoary bat).

Forearm <45 mm; upper parts reddish or mahogany ....................... 19

19. Upper parts brick red to rusty red, frequently washed with white ... 20

Upper parts mahogany washed with white.  Lasiurus seminolus (Seminole bat).

20. Color reddish with frosted appearance resulting from white-tipped hairs; interfemoral membrane fully haired.  Lasiurus borealis (eastern red bat).

Color rusty red to brownish without frosted appearance; posterior one-third of interfemoral membrane bare or only scantily haired.  Lasiurus blossevillii (western red bat).

21. Tragus (projection within ear) short, blunt, and curved ................ 22

Tragus long, pointed, and straight .................................................. 24

22. Forearm >40 mm.  Eptesicus fuscus (big brown bat).

Forearm <40 mm ........................................................................ 23

23. Forearm >32 mm; interfemoral membrane naked; color brown.  Nycticeius humeralis (evening bat).

Forearm <32 mm; interfemoral membrane lightly furred on anterior third of dorsal surface; color drab to smoke gray.  Parastrellus hesperus (American parastrelle).

24. Dorsal fur tricolored when parted (black at base, wide band of light yellowish brown in middle, tipped with slightly darker contrasting color); leading edge of wing membrane noticeably paler than rest of membrane.  Perimyotis subflavus (American perimyotis). 

Dorsal fur bicolored or unicolored with no light band in the middle; leading edge of wing same color as other parts of membrane ............................... 25

25. Calcar with well-marked keel ................................................... 26

Calcar without well-marked keel .................................................... 28

26. Forearm >36 mm; foot >8 mm long; underside of wing furred to elbow; pelage dark brown.  Myotis volans (long-legged myotis).

Forearm <36 mm; foot <8 mm long; underside of wing not furred to elbow; pelage light brown to buff brown ................................................... 27

27. Hairs on back with dull reddish brown tips; black mask not noticeable; thumb <4 mm long; naked part of snout about as long as width of nostrils when viewed from above.  Myotis californicus (California myotis).

Fur on back with long, glossy, brownish tips; black mask usually noticeable; thumb >4 mm long; naked part of snout approximately 1.5 times the width of the nostrils.  Myotis ciliolabrum (western small-footed myotis).

28. Forearm >40 mm .................................................................... 29

Forearm usually <40 mm ............................................................... 30

29. Conspicuous fringe of stiff hairs on free edge of interfemoral membrane.  Myotis thysanodes (fringed myotis).

No conspicuous fringe of stiff hairs on free edge of interfemoral membrane.  Myotis velifer (cave myotis).

30. In Texas occurring generally west of 100th meridian .................... 31

In Texas occurring generally east of 100th meridian .......................... 32

31. Dorsal fur usually with a slight sheen; forearm >36 mm; total length >80 mm.  Myotis occultus (southwestern little brown myotis).

Dorsal fur usually lacking a sheen; forearm <36 mm; total length <80 mm.  Myotis yumanensis (Yuma myotis).

32. Ear >16 mm, extending >2mm beyond nose when laid forward; tragus long (9-10 mm), thin, and somewhat sickle shaped.  Myotis septentrionalis (northern long-eared myotis).

Ear <16 mm, not extending >2 mm beyond nose when laid forward; tragus shorter and straight.  Myotis austroriparius (southeastern myotis).

 

Family Molossidae

FREE-TAILED BATS

Nearly 100 species of the family Molossidae, or free-tailed bats, are found worldwide, primarily in tropical and subtropical regions of the Old World and Mexico south through South America.  These bats are medium to large sized, insectivorous, and characterized by a tail that extends beyond the free edge of the uropatagium. 

Molossids are swift, strong fliers and often fly great distances between roosting and feeding sites.  Many species also make extensive migrations between winter and summer ranges.  Because of their narrow wings, free-tailed bats have difficulty taking off from the ground and often roost high in buildings, cliffs, and caves.  They require a free fall for takeoff to enable them to achieve sufficient momentum to sustain level flight. 

In North America, free-tailed bats occur from Canada to Mexico, but they are most common in the southern and southwestern regions of the United States.  Of the six species that occur in North America, four are known from Texas. 

 

Family Mormoopidae

LEAF-CHINNED BATS

Ten species of New World bats make up the family Mormoopidae, which includes the mustached, naked-backed, and ghost-faced bats that are variously distributed from the southern United States through Mexico, Central America, and South America to southern Brazil.  Characterized by fleshy appendages on the snout and chin and a short tail protruding dorsally from the interfermoral membrane, these bats are abundant in the tropics as well as semiarid and subtropical environments.  The only species of this family to occur in the United States is the ghost-faced bat, Mormoops megalophylla, which has been recorded in Texas and Arizona. 

 

Family Phyllostomidae

NEW WORLD LEAF-NOSED BATS

The Phyllostomidae are a large family of New World bats primarily limited to tropical and subtropical areas, although a few species reach northward to subtemperate areas in the United States.  The 160 species included in this family are characterized by a fleshy appendage, or nose leaf, projecting from the rostrum.  Most of these bats feed on fruit or nectar, but the family also contains a few insectivores, carnivores, and the true vampire bats.  Three species of phyllostomid bats have been recorded in Texas, including one vampire bat, but none is widely distributed or very common. 

 

Family Vespertilionidae

VESPER BATS

Chiefly insectivorous bats, the Vespertilionidae constitute the largest family of bats (>400 species) and are distributed worldwide with the exception of arctic regions.  Consequently, these bats are found in nearly every conceivable habitat from tropical forests to desert and temperate regions.  Many are highly migratory and traverse great distances between summer and winter ranges.  Others, however, do not migrate and instead hibernate on summer ranges.

Vespertilionids lack the facial adornments found in other familes of bats and are often referred to as plain-faced bats.  Several species have extremely large and complex ears, but most have small, simple ears.  These bats typically have small eyes and a long tail completely enclosed by a well-developed interfemoral membrane.  More than 33 species of vespertilionid bats range across the United States; of these, 25 are known from Texas.

Previous PageTable of ContentsNext Page

 

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.

Natural Science Research Laboratory