Area: Mojave and Sonoran Desert - SW United States and NW Mexico
Food: Herbivores, grass, cactus, herbs and wildflowers
Size: 10 - 14 inches and 4 - 6 inches in height
Desert tortoises can live up to 50-80 years! They grow slowly and have low reproductive rates. Desert tortoises spend most of their time in burrows, rock shelters, and pallets to regulate their body temperatures and to reduce water loss. They are most active after seasonal rains and are inactive during most of the year. This inactivity will help them reduce water loss during hot periods. They will also hibernate to survive freezing temperatures and low food availability.
Desert tortoises can tolerate water, salt, and energy imbalances on a daily basis which increases their lifespans. Their front limbs have sharp, claw like scales and are flattened for digging. Their back legs are skinnier and very long. Desert tortoises can live in areas with ground temperatures up to 140 degrees because of their ability to dig burrows underground to escape the heat. They will spend at least 95% of their lives in these burrows. This will also protect them from the freezing winter weather when dormant.
Desert tortoises have strong site fidelity and have well established home ranges where they know where their food, water, and mineral sources are. Their home ranges will consist of 10-100 acres. Males have larger home ranges than females and home range size increases with increasing resources and rainfall. Desert tortoises may consume soil to maintain adequate calcium levels so they prefer sites with higher calcium content.
Desert tortoises mate in the spring and autumn. Males grow two large white glands around the chin area called “chin glands” that signify the mating season. Females will lay a clutch of 4-8 hard shelled eggs which have the size and shape of ping pong balls. They will produce three clutches a year depending on the climate. Their eggs will incubate from 90-135 days. Temperature influences the hatchling rates and their gender.
Desert tortoises grow slowly and they take 16 years or longer to reach 8in. Their growth rate varies with age, location, gender, and precipitation. They will reach reproductive maturity at 15-20 years. Much of their water intake comes from their food. They have a large bladder that can store 40% of their body weight in water. Desert tortoises can survive a year or more without access to water.
Desert tortoises natural predators are ravens, gila monsters, kit foxes, badgers, roadrunners, coyotes and fire ants. Their populations have declined by as much as 90% since the 1980s and they are listed as threatened. It is illegal to touch, harm, or harass, wild desert tortoises. Their most significant human threats are habitat destruction, illegal collection and vandalism, wind and solar farms, and landfills.