With their club-like feet that are reminiscent of pachyderms, their slow and deliberate demeanor, and their preference for living on dry land, tortoises epitomize the terrestrial turtle. The family Testudinidae, the third most diverse family of chelonians, is represented on five different continents. Currently, the family Testudinidae includes thirteen genera and fifty species. At least 80 percent of tortoise diversity occurs in the southern latitudes including Africa, Madagascar, India, Southeast Asia, South America, the Seycehelles Islands, and the Galápagos Islands. The remaining portion of tortoise diversity lies within the southern United States, Mexico, southern Europe, and western Asia.
Tortoises possess distinctive physical characteristics that differentiate them from other chelonians. Their sturdy feet lack webbing, and the number of bones at the tip of the digits are absent or greatly reduced in number. These characteristics help the tortoise support its heavy, sometimes bulky, body on land.
Like many other groups of turtles, tortoises occupied a greater range during earlier times. Fossil evidence of tortoises comes from Eocene deposits some 55 to 34 million years ago. During this time, tortoises lived in northern Europe, Central Asia, and throughout most of North America including southern Canada as well as the West Indies. However, older fossils in Mongolia date back to the late Paleocene Epoch and indicate that these reptiles first appeared some 56 million years ago.
This specimen wanders across a road in South Texas. Roadway mortality accounts for most of the tortoise loss in Texas
Only one species of tortoise is known from Texas, the Texas tortoise. This modestly sized species can reach up to 8.75 inches (** cm). The carapace is is rounded in dorsal perspective almost as wide as it is long and ranges in coloration from dark brown with beige highlights appearing on the center of the costal and vertebral scutes and on the edges of the marginal scutes. The plastron is colored similarly to the carapace with dark brown to black present on the edge of the plastral scutes distal to the midline. The head, neck and limbs are can range in coloration from tan to dark brown with some specimens exhibiting black scales on the front of the limbs and bottom of the feet. A pair of mental glands can be seen on the lower jaws of adult specimens.
A view of prime tortoise habitat from Jim Hogg County, Texas
Within the United States, the Texas tortoise has a geographic distribution confined to southern Texas., Thisrange includes south of Del Rio and San Antonio. In Mexico the species is distributed from eastern Coahuila, nuevo Leon, Tamaulipas and northeastern San Luis Potosi. Within its range the Texas tortoise inhabits scrub forest, humid tropical zones and near desert situations with well drained soils.
Weather permiting, this species can be found active almost every month out of the year. Unlike other North American tortoises, the Texas tortoise does not excavate a burrow. Instead it may use a pre-dug mammal burrow or prepare a pallet in which to reside. Tortoise pallets are created by the tortoise using its forelimbs, gular scute and edges of the shell to scraped away an area near the base of a small tree, shrub or clump of cacti. The pallet has an upwards slope from its vegetative base. This form of refugia is most often used during the oppresively hot days of summer and during cold winter days. The largest pallet ever documented was one that measured * inches (10 cm) in depth and ** inches (33 cm) in length. (Auffenberg and Weaver, 1969)..
Mature males can be differentiated from females by having a cloacal opening that extends just beyond the carapacial rim and an elongated and forked gular scute that is used during bouts of territorial jousting between males and coercion of females that are reluctant to mate. Females dig a shallow nest site in sandy soil no more than 3 inches (* cm) deep and deposits 1-3 eggs. .