Introduction
The desert tortoise is one of the four species of on land tortoises in North America. They are the longest living reptile of the southwestern United States region, living from eighty years up to one hundred years. They are well adapted to living in a highly variable and often harsh environment.
On April 2, 1990; the U.S. Fish and Wildlife Service listed the desert tortoise as a threatened species. Their populations have been decreasing for many years due to habitat loss and disturbance, collection for pets, raven predation of eggs and juveniles, and a respiratory disease mostly caused by captive tortoises being released into the wild. It is illegal to collect desert tortoises from the wild without a permit from both the federal government and the states of California, Nevada, Utah, and Arizona.
It is also illegal to buy or sell desert tortoises. The only legal way for an individual to acquire a desert tortoise is to adopt one from a State Game and Fish sanctioned organization or to receive a captive-born hatchling as a gift.
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Appearance
Desert tortoises have a highly domed, distinctly ridged carapace ranging in length from 6 to 15 inches. Adults weigh in between 8 and 15 pounds. The carapace, which is the upper shell of a tortoise, is brown or horn colored. The plastron, the lower shell, is yellow-hued and without a hinge. Male tortoises have extended gular shields used in combat with other males during the breeding season. Both sexes have stout, elephant-like limbs which allows these reptiles access to an amazing range of microhabitats, from shallow desert washes to extremely steep mountainous slopes.
The desert tortoises scaly reptilian skin is tough and protects against water loss. Their sharp claws and strong legs provide the tools needed to dig deep burrows. One way to differentiate a male tortoise from a female is by size and tail length. The male should be both larger and have a longer tail than its female counterpart. Adult male tortoises also have a concave plastron used for mounting females during breeding season.
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Range
The natural range of the desert tortoise encompasses both the Sonoran and Mohave deserts in Southwestern Utah, Southern Nevada, Southeastern California, and Western Arizona in the United States. They also occur in the Sinaloan deserts in Northern Mexico.
To survive the harsh environment of the hot, dry desert; desert tortoises dig burrows under rocks or at the base of bushes. The tortoises need firm but not hard ground to dig through. Most burrows have a half-moon shaped opening and can be anywhere from 3 to 30 feet deep. The shorter burrows offer temporary shelter, while the longer ones called dens are used for hibernation. Desert Tortoises spend most of their lives underground.
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Behavior
The desert tortoise is most active during the day or the morning and evening, depending on the temperature. This tortoise spends most of its life underground. It burrows under the sand to protect itself from extreme desert temperatures, which range from 140 degrees Fahrenheit to well below freezing. Adults can survive for about a year without water. They produce a variety of sounds, including hisses and grunts. When in danger, tortoises can withdraw their head, legs, and tail into the shell.
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Breeding
The breeding season for desert tortoises runs from March to May. Some breeding activity may be noticed in the fall, but egg laying usually only takes place during the earlier parts of the year. The male will approach the female, bobbing his head vehemently. The female usually will attempt to move away from the male, forcing him to follow her. When the male finally corners the female, his head bobbing will increase, and he will begin circling the female, biting her head and forelegs. The male will then begin pushing into the female, forcing her to withdraw into her shell. When the female becomes quiet, the male will mount. About 25 to 40 days after copulation, the female turtle will finally be ready to lay her eggs. Nests usually are constructed along washes in nests scooped out of the ground. Incubation lasts 3-4 months with hatching from August to October. In addition to adequate amounts of suitable herbs, grass, or cactus for food, adequate soil moisture also is needed for the survival of tortoise eggs and young.
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Diet
The desert tortoise is herbivorous, feeding mostly on native grasses and leafy plants. In captivity they do well on a diet of grass or grass cuttings, and other garden plants, flowers and shrubs, greens and carrots. Lettuce is not sufficiently nutritious and should be avoided. Cactus fruits and vegetables should be fed in small amounts at most once a week.
In the wild, desert tortoises generally emerge from their burrows mid-March to feed on ephemeral plants. During a roughly six week period fresh green grass and spring wildflowers are their primary nutritional source. Dry stems of grass and cactus pads provide sustenance in dryer times. Introduced plant species have greatly intruded upon native plant species in the desert tortoises’ natural range, degrading the existing natural ecosystem.
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Conclusion
If properly cared for, a desert tortoise pet may well outlive its owner. The longevity of desert tortoises may tempt some individuals to release a captive tortoise into the wild if they no longer wish to care for it. Releasing captive desert tortoises into the wild should not be done under any circumstances to prevent upper respiratory tract disease (URTD), inappropriate genetic mixing, and the release of tortoises into an unsuitable habitat. Desert tortoises, with their ability to tolerate long periods of water and electrolyte imbalance, are among a unique group of animals adapted to the hostile climatic extremes of the North American deserts. Adopting a desert tortoise allows for a glimpse of the ecology that keeps these deserts alive, and is an educational experience for the entire family.
Science
