The Mojave desert tortoise occurs in the Mojave and Sonoran deserts north and west of the Colorado River in southwestern Utah, southern Nevada, southeastern California, and northwestern Arizona in the United States.
The Desert Tortoise is one of most elusive inhabitants
of the desert, spending up to 95% of its life underground.
The desert tortoise lives in a variety of habitats from
sandy flats to rocky foothills, including alluvial fans,
washes and canyons where suitable soils for den construction
might be found. It is found from near sea level to around
3,500 feet in elevation. Most desert visitors will not
see a tortoise. But if you plan your trip for early spring,
and are patient, you may see one of these popular residents
of the Mojave Desert.
The Desert Tortoise (Gopherus agassizii), has a high - domed shell and elephant-like legs and is easily distinguishable from its turtle cousins. They range in size from two inches up to 15 for a mature male. The top shells are brown, gray, or black, often with distinctive growth lines, while the shell underneath is lighter.
 Tortoises can completely withdraw their head and limbs within their shells, leaving only horny scales visible to predators. They have a short tail, and their claws aid them in digging burrows. Males have curved, longer gular horns which protrude from their lower shells underneath their neck and head. They use these horns to combat other males and for butting and nudging females during courtship. Males also have shallow depressions in their lower shells while the females' lower shell is flat. Most people can not tell the difference between male and female until they are15 to 20 years old or eight inches in length.
The desert tortoise produces a variety of sounds (hisses, grunts, pops, whoops, huhs, echs, bips, etc.) which seem to be the most important when vocalized to an unfamiliar tortoise. Social behavior consists of a series of head bobs for species and gender recognition, courtship, and threat. Head bobbing normally precedes agonistic (combative) behavior between males, although females may also be aggressive.
Desert tortoises may live 50 or more years in the wild. Their diet consists primarily of wildflowers, grasses, and cacti. Desert tortoises derive almost all their water intake from the plants they eat. A large urinary bladder can store over forty percent of the tortoise's body weight in water, urea, uric acid, and nitrogenous wastes. During periods of sufficient rainfall tortoises drink from temporary rain pools. A common defensive behavior when molested or handled is to empty the bladder, leaving the tortoise at a considerable disadvantage during dry periods. For this reason, desert tortoises should not be handled when encountered in the wild.
Reproduction begins between ages 12-20, with clutch sizes of 1-14 eggs. In years with low rainfall, females may lay few to no eggs . Females can store sperm for five years or longer, meaning they can reproduce for several years after mating. Nests are built and eggs are laid in late spring or early summer. The hatchlings appear in 90 to 120 days. The mother leaves the nest, so once the hatchlings appear, they must survive on their own.
Tortoises depend on bushes for shade and protection from predators such as ravens and coyotes. To escape the temperatures of cold winters and very hot summers, many tortoises live in burrows. The spring and summer burrows vary from 18 inches to five feet long, but may only be a few inches from the surface. Winter burrows tend to be about eight feet long and may be two to three feet from the surface. They often share burrows and may use multiple burrows scattered across the landscape. They hibernate for up to nine months each year, becoming most active from March to June and September to October. When they are young they seldom venture no more than 150 feet from their burrow. As they get older, they may go as far as 3/4 mile in a day and use a network of burrows. In the most densely populated areas, you may find one tortoise per 2.5 acres. Typically, tortoises densities are closer to one tortoise per 100 acres. |
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The
Heat Is On: Desert Tortoises and Survival
