Desert Tortoise

Mojave desert tortoise (Gopherus agassizii)

Sinaloan desert tortoise (Gopherus evgoodei)

Sonoran desert tortoise (Gopherus morafkai)

Reptile

Transcript:

Today on Animal Fact Files we’re discussing desert tortoises. Desert tortoises are part of the gopher tortoise genus and there are currently three living species: the Mojave desert tortoise, the Sinaloan desert tortoise, and the Sonoran desert tortoise. These reptiles live in the southwestern United States and northwestern Mexico. Here they reside in rocky foothills, sandy flats, desert canyons, and scrubby forests. The three species weren’t always separated, and they’re often difficult to tell apart due to hybridization between the species in captivity. Generally speaking, the Sinaloan desert tortoise has a flatter shell and the Sonoran desert tortoise has a narrower shell compared to the Mojave desert tortoise. That being said, it’s not easy to find a desert tortoise in the wild.

As recently as the 1970s, it wasn’t uncommon to see a desert tortoise in their natural habitat, but habitat loss, run-ins with cars, predators - like ravens who benefit from solar panels as perching spots, wildfires, and more have all hindered the desert tortoise populations. While these reptiles spend upwards of 95% of their time living in underground burrows, they take a long time to mature and reproduce. In some areas, it’s estimated about 90% of the adult population has been lost over the course of three generations. All of these threats combined have landed the Mojave desert tortoise as critically endangered and at least one of the other species as vulnerable to extinction.

It takes about twelve to twenty years for a desert tortoise to reach reproductive maturity. Males fight each other over females by ramming one another with their shells and attempting to flip an opponent on his back. The victor gets to mate as the loser takes his time getting himself turned over. Female desert tortoises can store sperm, so they often brumate prior to laying their eggs. Desert tortoises breed from spring to fall and spend the coldest parts of the year resting in self-dug burrows. In spring, the females emerge and dig out nests to lay their eggs. They urinate while digging, perhaps to keep the nest moist or to deter predators. She’ll stick around for a while after laying to ward off animals like beaded lizards looking to dig up her nest, but she eventually leaves the eggs on their own.

A desert tortoise clutch can have up to fifteen eggs but most often has between three to five. The eggs take two to over four months to hatch depending on temperature which also determines the sex of the babies. For their first five years of life, a desert tortoise’s shell is not fully hardened. They’re especially susceptible to predation during this time. Predators to desert tortoises include coyotes, foxes, bobcats, gila monsters, roadrunners, eagles, cougars, and more. Most don’t survive to twenty years of age, but those that do can live to be 80 years old!

While they aren’t nearly as large as a sulcata tortoise, desert tortoises weigh anywhere from 8 to 15 pounds (3.5-7kg). They range in shell length from half a foot to over a foot long (15-30cm) with males appearing larger than females. They’re not necessarily social animals, but they will rest in burrows with other members of their species especially during hibernation. Desert tortoises are herbivores and eat fruits, leaves, flowers, succulents, grasses and more. They drink a lot of water whenever it’s available and walk around with a full bladder that they can reabsorb if times get desperate. This is why it’s important not to approach a desert tortoise in the wild. If they release their bladder out of fear, it could be fatal!

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