Range:

Western California, southern Nevada, far southwestern and western Arizona, and southwestern tip of Utah

Habitat:

Scrubland and desert

A tortoise to talk about!

If you’ve ever visited the Mojave or Sonoran desert in California and saw a tortoise scooting across the sand, you most likely saw a desert tortoise. This tortoise species is a slow-growing, long-lived animal that has changed little during the past 200 million years. It is the largest terrestrial turtle in the United States and is a keystone species in the Mojave Desert ecosystem, providing burrows for other animals and dispersing seeds from eating the plants and grasses there.

The tortoise’s carapace (top shell) is usually brown or gray without any pattern, but it often may be brown or tan in the center of the shell. The plastron (underside) is yellowish or brownish. A desert tortoise has good hearing, but no external ear flaps. Its domed shell provides a large space for its lungs and for efficient thermoregulation, an important adaptation for life in the desert.

Built for desert life

The Mojave Desert’s summers are harsh, making it difficult to be active with temperatures reaching well above 105 degrees Fahrenheit (41 degrees Celsius) and with very little (if any) rain. Yet the desert tortoise is well adapted to deal with such extreme weather by going into estivation (decreased physiological activity) in a burrow during the extreme heat of the summer.

The animal’s front limbs are built like shovels, with long, sturdy nails that are good for digging. The large, cone-shaped scales on the limbs provide protection from the scratchy vegetation the tortoise may encounter and help the animal retain water. Cleverly, the tortoise digs basins in the soil to catch the infrequent rain that falls. The animal remembers where these “watering holes” are and walks directly to them after a bit of rain. Another water-saving tactic is storing up to 40 percent of its body weight in water inside the bladder, to be absorbed as necessary.

California’s state reptile is the desert tortoise.
A desert tortoise spends 95 percent of its life in a burrow.
A female desert tortoise can retain sperm and lay fertile eggs for up to 15 years after mating only one time with a male.
If you startle a wild desert tortoise, it could “void” or empty its bladder, leading to dehydration and possibly death.
Scientists believe that desert tortoises may live longer than humans.

The San Diego Zoo operates the Desert Tortoise Conservation Center (DTCC), located in Las Vegas, Nevada. The DTCC helps nearly 1,000 desert tortoises each year, including many acquired from people in Nevada’s Clark County turned in pet desert tortoises they didn’t want anymore or tortoises they found wandering in developed areas. Here are some stories about some of our favorite desert tortoises!

Monster

One massively large tortoise came to the DTCC from an abandoned, foreclosed home. We affectionately named him Monster, and we think he might be the largest desert tortoise on record! Since arriving at the DTCC, Monster has had his fair share of visitors! Seasonal staff members did a great job of digging him the largest burrow we’ve ever had. Monster adapted well to his new surroundings, and he’s always happy to come out and greet admirers!

Big Guy

Big Guy’s story began in 2010 when his custodian, Mona, could no longer care for him. Big Guy had been with Mona’s family for over 25 years, so she really wanted to keep him, but she knew life in an apartment was a bad idea for a tortoise. Big Guy was a prime example of great captive care: he was the right size, weight, and color, and he showed no signs of disease or lethargy, a perfect example of what happens when you give a tortoise the proper living conditions like a burrow and native foods.

Several months after Big Guy settled into his daily routine at the DTCC, the new owners of Big Guy’s former home in Las Vegas wanted to adopt him, with Mona’s blessing, of course! They went through the legal desert tortoise adoption process and learned how to care for a desert tortoise properly. Since desert tortoises can live for 80 to 100 years with the proper care, it is really important for anyone considering adoption to realize the huge commitment involved in adopting one. Desert tortoises also have very specific diet and habitat requirements, but the new owners were definitely up to the task. After renovating Big Guy’s original burrow and adding more native plants for him to munch on in the yard, these kind folks were approved for adoption.

Big Guy explored his new-and-improved surroundings and headed straight to his old burrow like he had never left. He also picked up his old habit of knocking at the back door with his beak when he wants to join his new family inside!

Twizzler

The DTCC has a number of special-needs desert tortoises that serve as wonderful education animals. Twizzler arrived here in 2007 with hardened gray material all over the left side of his carapace (top shell), causing a severe deformity. We later learned that he was part of a research project in the 1990s where researchers attached radio transmitters to young tortoises’ shells to track them using telemetry, and after the project was over or when they could no longer hear the signal, they abandoned the tortoises, sometimes without removing the epoxy that kept the transmitters attached! Since the epoxy covered a large portion of the shell, including the seams between the scutes (sections of the shell), the tortoises grew up with severe deformities, if they grew up at all.

Although no longer with us, the moral of Twizzler’s story is this: do not attach anything to a tortoise’s shell, especially if it touches the seams! And on that same note, never paint your tortoise. A tortoise’s shell is full of blood vessels, so toxins may be able to get into the bloodstream through small openings in the shell and along the seams where tortoises may have suffered even slight injuries in the past. Instead, if you want to easily identify your tortoise, use a nontoxic paint pen and write its name and your phone number on its shell so you will be able to get it back if it’s lost. And an even better option to prevent from losing your pet tortoise is to have your tortoise “microchipped” just like a veterinarian would put a microchip in your dog or cat!

Lucy and Ethel

These two females arrived at the DTCC with severe shell deformities, yellow skin, and eyes swollen so severely that they could barely open them. They were also so weak that they could not support their own weight enough to move about their enclosure. All of these signs indicate that Lucy and Ethel were definitely kept indoors for the majority of their lives so they didn’t get the proper heat and light and were not fed a well-balanced diet.

After weeks of providing them with the proper food, allowing them to bask outside daily in the sun’s natural rays, and soaking them every other day in a tub of water to help them establish and maintain hydration, they went from being marginally alive to interactive, beautiful eating machines. They changed from two very sick and depressed tortoises to two very energetic and healthy (though a bit deformed) big girls. Due to the severe deformities of their carapaces, they cannot be released back to the wild but are now used as education animals to show students and visitors the proper way to care for a tortoise…a valuable lesson for all.

Hear from our tortoise experts! Read the Desert Tortoise blog.

Declining populations
Once common throughout the Mojave and Sonoran desert of California, Nevada, and Arizona, wild desert tortoise populations have declined by an estimated 90 percent in the last 20 years. As the human population in these areas increases, the tortoise population has decreased. But how are humans causing this devastation? A number of culprits have been identified.

Off-road vehicles cause enormous damage to the desert plant community. When the plants are destroyed, the tortoises are without a source of food and water. It has been estimated that it can take up to 200 years for some of the destroyed habitat to recover. Off-road vehicles often run over tortoise burrows, crushing the animal inside. Large numbers of cattle graze on publicly owned deserts, depriving the tortoises of critical forage.

New housing developments and solar energy projects have sprung up around some of the older desert cities; much of this land is prime tortoise habitat. As a result of this building boom, large numbers of tortoises have been displaced or killed outright.

Increased human populations have brought an increase of predators that feed on human garbage and also forage throughout the desert. Ravens seek out newly hatched desert tortoises, while feral dogs easily kill and eat young tortoises and seriously maim or kill adult tortoises. There are now an estimated 150,000 wild desert tortoises living in critical habitat.

Desert Tortoise Conservation Center
Since 1989, the US government has protected desert tortoises. In 2009, San Diego Zoo Global partnered with the U.S. Fish and Wildlife Service, the Bureau of Land Management, and the Nevada Department of Wildlife to operate the Desert Tortoise Conservation Center (DTCC) to aid in the recovery of wild desert tortoise populations as well as the Mojave Desert ecosystem. Located in southwest Las Vegas, Nevada, the 222-acre property helps protect desert tortoises from the onslaught of real estate developments in the region. The Center offers ideal habitat for desert tortoises with sandy soil they can burrow into and plenty of desert plants to munch on.

The DTCC plays a critical role in the conservation of this iconic desert dweller. A large part of its work is directed at community outreach. For many years, visitors to the desert took tortoises home to keep as pets. One reason this isn’t a good idea is that people may not know how to take care of them. Desert tortoises can live for more than 100 years—who will take care of them all those years from now? It is also against the law to take a tortoise from its habitat.

All “rescued” tortoises are quarantined and given strict health assessments to avoid bringing diseases into the DTCC, as well as to prevent diseases from being transmitted to wild populations by translocated tortoises. Each tortoise is carefully screened and observed closely for months before it can be released into the desert.

Many former pet tortoises are brought in with advanced stages of metabolic bone disease because their owners kept them indoors their entire lives. These animals have never been exposed to natural heat, natural light, or healthy food, and, as a result, they are deformed with soft, discolored shells; they are not able to digest food properly; and their muscles have atrophied to the point where they can no longer support the weight of their own bodies. With proper heat, light, and nutrition, many of these same tortoises begin to flourish and may become candidates for release into protected native desert habitat.

The DTCC has hundreds of adult-sized pens and dozens of predator-proof enclosures for smaller desert tortoises, from tiny hatchling to three year olds. They can live safely and happily outside in the sunshine where all desert tortoises belong. In 2011, 236 desert tortoises were released into a protected area of the Mojave Desert, with transmitters attached to 36 of them so that staff can follow them and monitor their behavior. The DTCC continues to help desert tortoises recover and thrive, both at the Center and in their native habitat.

You can help!
How can you help desert tortoises? It is always important to reduce, reuse, and recycle in order to generate less waste and conserve our natural resources. If you see a desert tortoise in the wild, make sure to keep your distance. Even though you mean it no harm, being handled is frightening to a wild tortoise. It is also against the law to touch them.

If you or someone you know already has a desert tortoise and has been keeping it as a pet—keep taking care of it! Pet tortoises shouldn’t be “set free,” because they may introduce disease to the wild tortoises or be unable to survive on their own. Desert tortoises have been around for millions of years. We have to protect them so they will be here a long, long time to come.

You can help us bring desert tortoises back from the brink by supporting the San Diego Zoo Global Wildlife Conservancy. Together we can save and protect wildlife around the globe.