Desert Tortoise (Gopherus agassizii)                             

Key Characteristics:                                                                                                                                                                            Photo Credit:  David Hill

The Desert Tortoise is a species of tortoise native to the Sonoran and Mojave desert. It is one of 4 species known as gopher tortoises The desert tortoise ia a herbivore. Grasses form the bulk of its diet, but it also eats flowers, fruit, shrubs and cacti. Some rocks and soil are also ingested. As with birds, stones may also function as gastroliths, enabling more efficient digestion of plant material. Desert tortoises can grow from 4-6 inches in height and weigh 8-15 pounds when fully grown., and are characterized by brown shells. They may live 80-100 years.

Habitat:

In the Sonoran Desert tortoises inhabit gravely desert washes, canyon bottoms and rocky hillsides below 3530 ft. in Palo Verde and Saguaro Cactus communities. Nests are often dug near the burrow opening early in the season and further inside late in the season.

Adaptations to Desert Lining:

The desert tortoise is able to live where ground temperatures may exceed 140 degrees F. because of its ability to dig underground burrows and escape the heat. About 95% of its life is spent underground. It is also protected from freezing while dormant( winter torpor or brumation) in the winter. To maximize the utilization of infrequent rain fall, tortoises dig catchment basins in the soil, remember where they are , and may be found waiting by them when rain appears imminent. Water that reaches the bladder is not lost to the system but can be drawn upon as needed. Adult tortoises may survive a year or more without access to water. The majority of the tortoise’s water comes from grasses and wildflowers they consume in the spring. It is believed that, in their entire lives, these tortoise rarely move more than two miles from their natal nest.

Description:

The carapace of these tortoises may attain a length of 6-15 inches . Male tortoises have a longer gular horn than females. Males use this in fighting with other males, attempting to flip the other male on its back. The mating season for the desert tortoise is lengthy. The eggs are incubated from 90-120 days. Hatchlings from only a few eggs out of every hundred , actually survive the 7-15 years it takes to reach adulthood. Ravens, Gila monsters, kit foxes, badgers, roadrunners, coyotes, and fire ants are all natural predators of the desert tortoise. One defense mechanism the tortoise has when it is handled or molested is to empty its bladder. This can leave the tortoise in a very vulnerable condition in dry areas. Tortoises should never be alarmed, handled or picked up in the wild. It is unlawful to touch, harm, harass, or collect desert tortoises. The desert tortoise populations have declines by 90% since the 1980s.

I found this organism to be really interesting because:

While hiking on the Quartz trail back in 1999, when the draught was at its peak, we came across a desert tortoise in this rocky, dusty, barren, arid , and hostile environment . I was struck by the resilience of this creature to survive in such a place.

Author:  Glenn Tueffle

References: Wikipedia; Desert USA