|The Mammals of Texas -
Llano Pocket Gopher
Rodentia : Family Geomyidae : Geomys
Description. A cryptic species
bursarius and G. knoxjonesi. Morphologically, the Llano pocket gopher is
slightly smaller than the plains pocket gopher but
biochemical study is required to reliably separate the
two. Dental formula as in G. bursarius.
Distribution in Texas. Occurs only in two
isolated areas of the Texas Hill Country. Records are
from McCulloch, San Saba, Mason, Llano, Gillespie,
Uvalde, Zavala, and Medina counties.
Habits. The natural history of G.
texensis is undoubtedly 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 clayey soils.
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 this area contained no embryos and showed
no signs of reproductive activity.
Remarks. Scott Block and Earl
Zimmerman theorize that increasing warmer and drier
periods in Texas climate beginning about 10,000 years ago
may have led to the geographic isolation of this 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.