Desert Tortoise
Gopherus agassizii
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The desert tortoise is a large herbivore and the official reptile in the states of California and Nevada. No other tortoise in North America shares the extreme conditions of habitats occupied by the desert tortoise. The desert tortoise has a high domed shell, or carapace, that is greenish to dark brown in color. Its front limbs have heavy, claw-like scales and their flat shapes are well-designed for digging.
Height 4- 6 inches
Length 9-15 inches (carapace)
Weight 8-15 lbs
Lifespan 50-80 years
Diet
Varies throughout the tortoise's range. Herbs, grasses, some shrubs and the new growth of cacti and their flowers
Population
The number of desert tortoises has decreased by 90% since the 1950’s. Recent estimates indicate that there are about 100,000 individual desert tortoises existing in the Mojave and Sonoran deserts. As late as the 1950’s the desert tortoise population averaged at least 200 adults per square mile. More recent studies show the level is now between 5-60 adults per square mile.
Range
The Desert Tortoise can be found in the Mojave and Sonoran Deserts of southern California, Nevada and Utah. They inhabit semi-arid grasslands, desert washes and sandy canyon bottoms below 3,500 ft.
Behavior
The desert tortoise is able to live where ground temperatures may exceed 140 degrees F because of its ability to dig underground burrows to escape the heat. It is one of the most elusive inhabitants of the desert, spending up to 95% of its time under ground to escape the heat of the summer and the cold of winter. They live in burrows which they dig. These can be 3-6 feet deep. They will spend November through February in a torpid or dormant state in their underground burrows.
Their most active time is in the spring when they will forage for food. During the hottest, driest periods of the year the tortoise conserves water already stored in its body. This is especially important in the hot, dry Mojave Desert summers. Winter hibernation aids in minimizing water loss.
Much of
the tortoise’s water intake comes from moisture in the grasses and wildflowers
they consume in the spring. To maximize the utilization of infrequent rainfall,
tortoises dig catchment basins in the soil, remember where these are, and may be
found waiting by them when rain appears imminent. Water that reaches the bladder
is not lost to the system but can be drawn upon as needed. Adult tortoises may
survive a year or more without access to water.
Reproduction
Mating
Season Late summer to early fall
Gestation 10-12 months
Clutch size 4-6
eggs
Females do not breed until they are 15 to 20 years old. Survival of
juveniles is low: only 2-3 per 100 hatched may live to become adults.
Threats
The desert tortoise is very sensitive to human disturbances, and
this has led to the decimation of many of its populations throughout the desert
southwest. Increased urban development in the deserts of California and other
states have fragmented and reduced suitable habitat. Certain fatal diseases
appear to be spreading among tortoise populations. Poaching, the use of
off-highway vehicles within tortoise habitat and crushing by automobiles have
also continued to threaten tortoise populations.
Ravens cause significant
levels of juvenile tortoise predation in some areas of the Mojave Desert with
more prevalence of human disturbances.
Legal Status/Protection
The Desert Tortoise is federally threatened species under the *Endangered Species Act.
* The Endangered Species Act requires the US federal government to identify species threatened with extinction, identify habitat they need to survive, and help protect both. In doing so, the Act works to ensure the basic health of our natural ecosystems and protect the legacy of conservation we leave to our children and grandchildren.
How You Can Help
- Help Desert Tortoises and other wildlife by adopting an animal at our Wildlife Adoption Center.
- Take Action for Wildlife at our Wildlife Action Center.
For additional information
Visit Defenders' Imperiled Species: Desert Tortoise pages for more information about what Defenders is doing to help.
Desert Tortoise Data & Information
Desert Tortoise Preserve
Committee
U.S. Fish & Wildlife Service
Western Ecological Research
Center
