Basic Facts About Desert Tortoises

The desert tortoise (Gopherus agassizii) 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.

© Jonathan S. Blair / National Geographic Stock

Diet

Varies throughout the desert tortoise's range. A desert tortoise's diet may include 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 themselves. 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 their use 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.