Wildlife Discovery: Desert Tortoise

Tortoises are the land-dwelling turtles of the family Testudinidae. The Desert Tortoise is one of four species of the genus Gopherus, known collectively as gopher tortoises. Brown shells 8-15 inches long with flattened front limbs adapted for burrowing characterize gopher tortoises. A tortoise is a high-domed turtle, with elephant-shaped, or “columnar,” legs. It is more terrestrial than the turtle is, going to water only to drink or bathe. Tortoises do not have bodies designed for swimming. They do not have webbed feet, rather their feet are round and stumpy for walking on land, and they are not able to swim. The Desert Tortoise is an herbivore that may attain a length of 9 to 15 inches in upper shell (carapace) length. The tortoise is able to live where ground temperatures may exceed 140 degrees F, because of its ability to dig underground burrows and escape the heat. At least 95% of its life is spent in burrows. There, it is also protected from freezing while dormant, November through February or March.The Sonoran Desert Tortoise is flat and pear-shaped, compared to the Western Mojave tortoise, which is more of a butterball shape; they are usually active in spring. The Sonoran Desert tortoise is more active in summer and seeks shade under large rocks and boulders. Northern and southern Desert Tortoises may one day designate as different species or subspecies. Desert Tortoises make hisses, pops and poink sounds, perhaps as fear and distress calls. Males too grunt when mating. The tortoise’s hind limbs differ markedly from the forelimbs. Whereas the hind limbs are elephantine, the forelimbs are flat with well-developed muscle. They them for digging burrows. The females use their hind limbs to dig their nests. Desert tortoises inhabit semi-arid grasslands, gravelly desert washes, canyon bottoms and rocky hillsides below 3,530 ft. Tortoises north and west of the Colorado River inhabit valleys and on alluvial fans. In the Sonoran Desert of Arizona, however, the tortoises tend to live on steep, rocky hillside slopes in Palo Verde and Saguaro Cactus communities. Diet composition varies throughout the tortoise’s range. If winter rainfall has been sufficient to result in germination of annuals, they are used heavily when the tortoises emerge from winter torpor (brumation). Other herbs, grasses, some shrubs and the new growth of cacti and their flowers comprise a major portion of the diet. If there is no summer rain, tortoises will utilize dry forage. Ends