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LLANO POCKET GOPHER
Geomys texensis Merriam 1895

Order Rodentia : Family Geomyidae

DESCRIPTION. A cryptic species of the plains pocket gopher, formerly recognized as a subspecies of G. bursarius (see "Remarks"). Morphologically, the Llano pocket gopher is slightly smaller than the plains pocket gopher, but molecular data are required to reliably distinguish the two species. Dental formula: I 1/1, C 0/0, Pm 1/1, M 3/3 × 2 = 20

Geomys texensis

DISTRIBUTION. Occurs primarily in two apparently isolated areas of the Texas Hill Country. A small area of distribution occurs in Medina, Uvalde, and Zavala counties. In the central Hill Country, recent records from Coleman, Lampasas, Blanco, and Kimble counties have extended the known range north, east, and west. Like G. attwateri, this species is unique to Texas; it occurs nowhere else in the world.

Distribution of Geomys texensis

SUBSPECIES. There are two subspecies: G. t. texensis in the Hill Country, and G. t. bakeri in South Texas (Medina, Uvalde, and Zavala counties). A third subspecies, G. t. llanensis (from Mason and Llano counties), has been recognized by some authorities.

HABITS. The natural history of G. texensis is similar to that of G. bursarius. The Llano pocket gopher is found in deep, brown loamy sands or gravelly sandy loams and is isolated from other species of Geomys by intervening shallow, stony to gravelly, clay soils. Geomys texensis may be found inhabiting valley areas and fluvial soils at the margins of rivers and streams as well as city parks, lawns, and roadside drainage ditches.

Five specimens in the Texas Cooperative Wildlife Collection at Texas A&M University, collected in Llano County in mid-March, were reproductively active when captured. One contained three embryos, one had two embryos, one was inseminated, one was lactating, and the fifth was pregnant with "very small embryos." A sixth specimen from the area contained no embryos and showed no signs of reproductive activity.

POPULATION STATUS. Uncommon. This species is locally abundant but has a patchy distribution throughout its range.

CONSERVATION STATUS. The IUCN lists the Llano pocket gopher as a species of least concern, and it does not appear on the federal or state lists of concerned species. The subspecies in the Hill Country, G. t. texensis, is locally abundant and does not appear to be threatened. Populations from Sycamore Creek and the Rio Grande are now extinct because of the flooding of their habitat when the Amistad Reservoir was created. Populations of G. t. bakeri, a recently described subspecies, occur in patchily distributed soils along separate drainages of the Frio River. Given the limited distribution of this species and its subspecies, periodic monitoring is recommended.

REMARKS. In 1991, Scott Block and Earl Zimmerman (North Texas State University) elevated G. texensis from a subspecies of G. bursarius. Further, they theorized that increasing warmer and drier periods in Texas climate beginning about 10,000 years ago may have led to the geographic isolation of the Llano pocket gopher. As lengthy drought cycles caused accelerated soil erosion and a decrease in the former mesic vegetation of western Texas, the increasingly xeric conditions may have served to help isolate G.texensis in the small range seen today and contributed to its speciation.

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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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