Description and Identification

With a large shell up to 15" in length, this land tortoise has a domed carapace that is marked by distinct growth rings. Coloration can be horn, orange-brown, gray-brown, dark gray. The underside of the shell is usually tan or yellow. The tail is short. The hind limbs are also short but rounded and thick. The forelimbs are flattened for digging, are longer than the hind limbs. The forelimbs are armored with large, thick scales. The head is relatively small and rounded. In males the gular shields of the plastron extend out underneath the throat more so then the females. G. agassizii has a wider shell width then the Sonoran Desert Tortoise (Gopherus morafkai), making G. agassizii look more butterball-shaped.

Distribution

Gopherus agassizii is distributed in western Arizona, southeastern California, southern Nevada, and southwestern Utah. Mohave Desert.

Native Habitat

Mojave Desert Tortoises can inhabit semi-arid grasslands, gravelly desert washes and sandy canyon bottoms. They have a strong proclivity in the Mojave Desert for washes and canyons where more suitable soils for den construction might be found. Tortoises show very strong site fidelity, and have well-established home ranges in which they know where their food, water and mineral resources are and who their neighbors are. Some of the highest densities of desert tortoises occur in creosotebush and creosotebush-white bursage (Ambrosia dumosa) vegetation in the western Mojave Desert.

Wild Diet

Gopherus agassizii is herbivorous, feeding on grasses, herbs, annual wildflowers, and new growth of cacti, as well as their fruit and flowers. Rocks and soil are also ingested, perhaps as a means of maintaining intestinal digestive bacteria or as a source of supplementary calcium or other minerals. These tortoises are able to conserve water due to their large urinary bladder. Most of their water intake comes from the plants and cacti they consume but during monsoon rains they can be found drinking from pools of water. Mojave Desert Tortoises are scavengers and will also feed on small berries, fruits, carrion, and excrement.

Behavior

The Mojave Desert Tortoise is terrestrial, spending most of its life in underground burrows. The feeding and activity period of this species is very short, and mostly restricted to spring. It is most active during the day in spring, early summer, and during summer rains, becoming more active in early morning and late afternoon as seasonal temperatures increase. There may be another period of activity in the early fall as new sprouts germinate. Winter hibernation begins from October to November, and often occurs in a communal den.

Reproduction

Gopherus agassizii lays more clutches per year than Gopherus morafkai (Sonoran Desert Tortoise). Courtship and breeding occur soon after emergence from hibernation in March and April. Males combat each other for access to females, using their enlarged gular horns to ram and possibly overturn another tortoise. A tortoise that cannot right itself is in danger of dying from overexposure to the sun. Females lay a clutch of 1-6 eggs from May to July, usually at the opening of or just inside a burrow. 1-3 clutches may be laid each year. The eggs typically hatch from mid August to October.