California Desert District
The desert tortoise lives in the Mojave and Sonoran deserts. These two deserts are in southern California, southern Nevada, Arizona, the southwestern tip of Utah, and Sonora and northern Sinaloa, Mexico. The Mojave population (Gopherus agassizii) of the desert tortoise is found north and west of the Colorado River. It was listed as "threatened" under the California Endangered Species Act in 1989 and the federal Endangered Species Act in 1990.
The desert tortoise is between 8 and 15 inches long. It is the largest reptile in the Mojave Desert. The shell is domed and horn-colored or brown. They typically live an average of eighty years, but may live to reach one hundred years old. The average age for females to start reproducing is between 12 and 20 when they lay a clutch of eggs (up to 15) in the spring.
Juvenile Desert Tortoise
The desert tortoise is well adapted to life in the desert. There are many plants in the desert which the desert tortoise eats: cactus, annual forbs, grasses, and wildflowers. In the spring (from March to June) they forage; they are building up stores of fat and water for the rest of the year.
Desert tortoises live in burrows which they dig to escape summer heat and winter cold. When it gets very hot in the summer they estivate in these underground burrows. In the fall, when it is cooler, the desert tortoise will again emerge and eat dried grasses and drink after a thunderstorm.
When there is no water available they are able to absorb the water from their bladders. Watch out, you do not want to approach a desert tortoise too closely; when frightened, they may release their bladder and lose this vital water supply.
In the winter (October to March) they return to their burrows to hibernate. Some burrows have been passed down through generations of tortoises.
Desert Tortoise Feeding
The Mojave population lives primarily on flats and alluvial fans. Common traits of these areas are scattered shrubs with abundant inter-space for growth of herbaceous plants, with soils ranging from sand to sandy-gravel. There is, however, significant geographic variation in the way desert tortoises use available resources; they are also found on rocky terrain and slopes.
Critical habitat designation for the Mojave desert tortoise was published in the Federal Register in February 1994 (59 FR 5820). Areas within the Mojave and Colorado deserts that are essential for the species' recovery were designated critical habitat.