Description: The Sonoran Desert Tortoise is a large (up to 12.5 inches) terrestrial turtle with a rough carapace that is gray to orange-brown, the plastron is not hinged, the hind limbs are elephantine, the front feet are shovel-like, and a prominent median projection extends forward from the front of the plastron (gular shuield). The digits of the feet are not webbed.

Habitat: This tortoise occurs in upland habitats of the Sonoran desert scrub in areas with rocky outcrops and palo verde-saguaro cactus communities and ecoltonal desert grasslands. Within these habitats, it generally occurs along rocky slopes, or bajadas, of desert mountain ranges. Low density population occur along alluvial fans and in intermountain valleys where desert washes and associated caliche caves provide suitable habitat and shelters. These lowland population provide important linakes among disjunct mountain ranges. In southern Sonora and Sinaloa, tortoises occur in seaside scrub thornbush, Sinaloan thornscrub, Sinaloan deciduous forest associations, and the edges of oak/juniper woodlands (2,500 ft elevation), with most tortoise localities between 1,000 to 1,600 ft elevations.

Sonoran tortoises often retreat into rock crevices or small pallets wedged under boulders, rather than digging deep burrows. On the Florence Military Reservation in south/central Arizona, tortoises concentrated around incised washes with dense caliche caves or near a volcanic hill; tortoises selected incised washes over the other habitat types but apparently avoided washes with few caliche caves. Thus availability of shelter sites may strongly influence tortoise distribution and abundance.

Range: G. morafkai occurs east of the Colorado River in Arizona, as well as in the states of Sonora and Sinaloa, Mexico.

Found in these States: AZ

Diet: Tortoises forage primarily on native winter and summer annuals (dicots and grasses), perennial grasses, cacti, and other vegetation, including a few perennial shrubs in descending order of preference. Insects also may be eaten, and caterpillars and other insect larvae may occasionally provide rich lipid and protein supplements to an otherwise vegetarian diet; these may be especially valuable to juvenile growth. Desert tortoises and the closely allied Texas tortoise have been observed biting road-killed anurans and lizards.

Hatchling or neonate (first year) congeneric gopher tortoises conserved about half of the lipid energy in their residual yolk at the time of hatching. In most cases these reserves are significant and could provide energy for early growth and first burrow construction or elaboration, even during a dry fall hatching season when little or no palatable forage is available. Hatchlings have been known to overwinter in their egg nests before emergence, sustained by residual yolk lipids. Another source of hatchling nutrition (in the absence of fresh forage) is feces of conspecific adults. Cprophagy may provide bacterial protein, inoculation of mutualistic fermenting anaerobes (Clostridium) that assist in later cellulose digestion, and may provide rich supplies of calcium, magnesium, and vitamin B complex as they do for small coprophagous mammals. In the Arizona and Mexican portions of the range, fall forage is available to emergent hatchlings as a result of late summer monsoonal rains. More general proclivities toward coprophagy have also been reported for adults; these cases may involve ingestion of tortoise feces and wild and domestic mammal feces as well.

Diet may change in response to the changing abundance of food items with different seasons. Tortoise diets also are influenced by the differences in available forage between wet and dry years. Wet springs and by extension, wet years, provide a greater biomass of annuals for a longer period of time. Variation in diet is also related to location and habitat. Generally, annuals dominate spring diets, while dry grasses and cactus dominate the summer diet. Dietary potassium affects the choice of food items, seasonal shifts in choices, seasonality of feeding, nitrogen retention, growth, with high loads inhibiting many of these processes.

Reproduction: Courtship and breeding occur in July to September. Adult females produce a single clutch in late spring every 1 to 2 years. Clutch size is 1 to 12 (mean around 6). Estimates of mean age of sexual maturity were 13.8 years in Sinaloa, 15.7 years in the Sonoran Desert. Tortoises with straight plastron midline lengths larger than 7.85 inches are generally sexually mature, including males in which plastron concavity is not conspicuous.

Status: Declines have resulted from myriad factors, including habitat loss, degradation, and fragmentation caused by urbanization, agricultural development, livestock and feral burro grazing, invasion of exotic annuals (which fuel local fires), energy and mineral development, and ORV use; mortality on roads; disease; vandalism (illegal shooting); and collecting. These factors vary regionally in their severity. Sonoran Desert Tortoise populations apparently have not been negatively affected by habitat loss or respiratory disease to the same degree as have populations of G. agassizii in the Mojave and Colorado deserts, though local losses have occurred.

Subspecies: None

Taxonomy: In 2011, on the basis of DNA, geographic, and behavioral differences between desert tortoises east and west of the Colorado River, it was decided that two species of desert tortoises exist: Mojave desert tortoise (Gopherus agassizii) and Sonoran desert tortoise (Gopherus morafkai).