Binghamton Zoo Animals

Desert Tortoise
(Gopherus agassizii)

Order: Testudines
Family: Testudinidae
Genus: Gopherus
Species: Gopherus agassizii

HABITAT AND RANGE: Desert tortoises live in different habitats in different parts of their range. There are three distinct populations of desert tortoises, including the Sonoron desert tortoises (northern most), Mohave desert tortoises, and the Sinaloan desert tortoises (southern most). The distinction between these tortoises is where they live. They range from California, Nevada, and Utah south to northern Sinaloa and southern Sonora.

PHYSICAL CHARACTERISTICS: The head of a desert tortoise is scaly, and the body has thick skin. Desert tortoises also have extremely long nails that are used in digging through the desert sand to find shelter. The upper shell of a desert tortoise ranges in length from 15 to 36 centimeters, and its color varies from dull brown to a dull yellow. Males are typically larger than females. An adult male desert tortoise averages around 20 kilograms in weight, and an adult female averages 13 kilograms. Males and females are also shaped differently. Male tortoises have long curved horns that are used for leverage in male-male combat, heavier claws, and longer tails that facilitate copulation. Each male tortoise also has a depression in the plastron that fits around the carapace of a female, and an inward curve at the rear portion of the carapace that allows him to achieve the upright position needed for mating. Females, on the other hand, have carapaces that curve outward and flat plastrons.

ADAPTATIONS: Female desert tortoises provide their young with yolk, which not only sustains them while the eggs incubate, but which provides the hatchlings with enough energy for six months (enough to sustain them in case they are not able to feed before hibernating). Desert tortoises perceive the world using visual, chemical, tactile, and auditory senses. They communicate with one another by vocalizing and posturing, and they may use feces and anal gland secretions to mark their burrows and home ranges. In the past, desert tortoises were used by indigenous peoples of the American Southwest for food and medicine, and the shells were used to make bowls, ladles, and shovels. Tortoises will urinate as a last line of defense when handling.

DIET:  Desert tortoises are herbivorous, surviving on low-growing plants and freshly fallen leaves. They also drink large amounts of water from temporary pools.

REPRODUCTION AND DEVELOPMENT: Desert tortoises have multiple mates during their lifetime. During the breeding season, males fight one another for access to receptive females. During combat, males posture, bob their heads, ram into one another, and chase one another. Desert tortoises breed from spring to fall. Each female desert tortoise lays 1 to 14 (most commonly, 3 to 5) round, off-white eggs. Females in the Mohave desert often lay a second clutch in late summer, which may not hatch until the next spring. The shell of a newly hatched tortoise is extremely soft and remains soft during the first five years of life, but eventually hardens as the tortoise matures. Although the mortality rate for young desert tortoises is very high, the life expectancy of desert tortoises that live past age 20 is 50 to 80 years.

STATUS IN WILD: Threatened