Desert Tortoises

Desert Tortoises


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As Yun Zi discovered in 2010, a new location can deliver better views!

As Yun Zi discovered in 2010, a new location can deliver better views!

We’re excited to announce a new home for stories and updates about the animals and conservation work of San Diego Zoo Global: the ZOONOOZ website!  For the first time, the amazing stories, photos, and videos that have only been available via our printed magazine and app will be available to just about everyone. Anyone with a web browser—on any device—can enjoy the fun, interesting, and informative tales we share.

Blogs published in 2015 have been re-homed at the new location, and this site will continue to exist as an archive of past years’ stories and information.

The search function on the new site will help you find stories about the species you particularly enjoy reading about, but we encourage everyone to explore and scroll through the topic headings—you’re sure to discover some new favorites!


The World for a Desert Tortoise

Tortoise Montana shared some attitude with Paul.

Tortoise Montana shared some attitude with Paul.

While working at San Diego Zoo Global’s Desert Tortoise Conservation Center in Las Vegas, I have handled over a thousand desert tortoises. All of them are important to me. One function of my job is to find tortoises and bring them in for medical check-ups, evaluations, and preparation for relocation into the wild. Most desert tortoises are calm, curious, and easy to handle if you are nonthreatening. One tortoise, however, stands out among them all.

Early April. I had to go into Pen #362, find tortoise #17894, and bring her in for medical check-up. The tortoise was in an artificial burrow. I got on the ground, flipped on my flashlight, and prepared for the rough work of trying to coerce a well-dug-in tortoise to come out. Suddenly, one fierce reptile charged out! She scampered all the way from the back of the burrow, legs swimming through dirt and pebbles. She ran at me as if she wanted to fight! All I could think of was Al Pacino, as Tony Montana in the movie Scarface, confronting me. She seemed to be saying “You want to mess with me!? O-kay! You think you’re tough!? O-kay!” I picked up the tortoise, her legs flailing while trying to get at me. From now on, #17984 is Tortoise Montana!

She's now more relaxed around him.

She’s now more relaxed around him.

After her check-up, she was placed back into pen #362. I fed her in the mornings, and over time she became more agreeable to my presence. By June, my route had changed and others fed Tortoise Montana, but I would occasionally go visit her whenever I could. Instead of charging out, she would calmly walk out of the burrow to come near me. Sometimes, if I had extra food, I would make a special trip to her pen to let her have it. One morning, I watched her drink from a puddle of water created by the irrigation drip system. During the heat of summer she usually slept in the back of her burrow. I asked a colleague about her status. She was healthy and would soon be translocated to the desert!

September: Translocation Week. Many tortoises were brought into the lab for their preparation. My job is to put translocation ID tags on the tortoises’ shell. I scanned the lab. There she was! A plastic box tote labeled 17894 362! I opened the tote. While sitting on her bed of hay, she was relaxed and stayed still as I applied the tag.

Paul attaches a translocation ID tag on a desert tortoise.

Paul attaches a translocation ID tag on a desert tortoise.

The next day I traveled with my colleagues out to Eldorado Valley. I knew Tortoise Montana was in the last pickup truck of our convoy. After we arrived at the release site, while gathering the tortoises, I found her tote and placed her at the front of the line for fluids. Afterward, I picked up her tote and walked into the desert with her. I eventually found a shady spot that had lots of desert flora and grass. I lifted Tortoise Montana, looked into her eyes, and gently placed her on shady ground. I filled out her data sheet, made my observations, and said “good-bye” as she looked around at her new home.

Whenever I walk by pen #362 I feel a little sad. The pen is empty now. But I feel good, too, because I know Tortoise Montana has what I know she needs: “The world…and everything in it.”

Paul Griese is a research assistant at the San Diego Zoo’s Desert Tortoise Conservation Center. Read his previous post, Burrowing Owl: Who Are You?


Volunteers Help Desert Tortoises

Volunteer Kimi Sharma won a contest for most volunteer hours worked in June: 71 hours!

Volunteer Kimi Sharma checks on a resident of the Desert Tortoise Conservation Center.

I’m always amazed to see volunteers bouncing into the Desert Tortoise Conservation Center at 5 a.m. to start the day. Most of our volunteers drive long distances to give of their time and help the tortoises. We had wonderful volunteers this season, all very dedicated! They have already put in over 600 hours so far this season!

Our volunteer coordinator, Lori Scott, did a great job coordinating, orientating, and keeping up with the various schedules of the volunteers. Lori’s job was to also make sure they felt appreciated and were gaining a valuable experience. Kimi Sharma won a contest for most volunteer hours worked in June: 71 hours! Before Kimi left to head back to school in Boston, she had acquired 155.5 hours of volunteer work. Kimi was kind enough to bring all of us lunch on her last day, which we appreciated very much…I don’t think she really wanted to leave!

The volunteers work really hard in the hot summer sun right along with staff watering, feeding, and helping us care for all the desert tortoises on site. We appreciate every hour the volunteers give of their time to help out the tortoises they care for. Volunteers help us out tremendously, and we couldn’t do our job without them!

We are now gearing up for translocation season and are always looking for volunteers to help out—it’s such an awarding experience! If you are in or going to be in the Las Vegas area and wish to help with volunteering, email us at

Angie Covert is a research coordinator at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Internship at Desert Tortoise Conservation Center.


Tortoise Fight

Two desert tortoises duke it out.

Two desert tortoises duke it out.

The day started in the perfectly normal manner. Hopping out of bed at 3 a.m., I cruised on through the morning schedule. Pack? Check. Water? Check. Sunblock? Check. As I walk out the door, my cat yawns and glares at me, implying “You DO know the sun’s not up yet, right?”

Once out in the field, I greet the sun rising over the Spring Mountains with the usual smile. Week after week, I track the movement of transmitter-wearing desert tortoises for the San Diego Zoo’s Desert Tortoise Conservation Center. In short, I hike a lot. However, don’t let me fool you; it’s anything but dull. That’s the beauty of working with living creatures—you never know when you’ll experience something extraordinary. And that’s just what happened that perfectly normal day in the field.

Raising my antenna, I punched the frequency for tortoise #21 into the receiver. After following the signal and tone, I finally approached #21 digging on the apron of a soil borrow. “And another one down,” I thought to myself as I kneeled down to take a GPS point. That’s when I noticed the second tortoise in the mouth of the burrow. I leaned in close, inspecting its carapace. This tortoise had been notched and tagged already, the usual procedure when we come across a resident in the field: #25. I was so caught up with identifying #25 that I hardly noticed #21’s movement until it was butting against the side of my boot. “Whoa, buddy!” Someone was clearly in a feisty mood.

I quickly finished taking my GPS point and moved away to complete the datasheet. Suddenly, I heard scuttling, scratching, and the movement of dirt coming from the direction of the tortoises. “What is going on?” I wondered, and I moved back within eyeshot of the burrow.

I froze. The tortoises were fighting! After inspecting me, #21 had proceeded to move back to the burrow and pick a fight with the larger #25. They were really going at it, their hard shells knocking together with a sharp “crack” upon contact. I initially thought I was witnessing a male versus male brawl but was surprised to discover that #21 was a female! Click on the video link below to watch…

Desert tortoise fight

Shortly thereafter, the two broke apart. I wasn’t sure if I was viewing the tortoise reenactment of “Hit the road, Jack,” but I used the pause to grab my camera in anticipation of round two. Sure enough, they collided again, pushing with their heads and the front of their shells, often lifting each other on their hind limbs due to the force. Finally, the male, #25, managed to flip the female, #21, over the edge of the burrow apron. I stopped recording and rushed to a new spot to see her. She was now on her back, but she wasn’t about to back down. She slowly righted herself on her feet, ready for round three. After several more minutes of tussling, #25 finally backed away, turned around, and moved away from the dirt burrow. Meanwhile, #21 stood triumphantly on her burrow apron watching him meander off. How’s that for a bit of spring cleaning?

I smiled, shook my head, and finished filling out the data sheet. I punched in the numbers for the frequency of the next tortoise on the list, picked up my pack, and held up the antenna.

Yep, just another perfectly normal day…

Tiffany Pereira is a research associated at the San Diego Zoo’s Desert Tortoise Conservation Center.


Look under Your Vehicle!

A desert lizard seeks shade under the tire of a truck.

A desert horned lizard seeks safety under the tire of a truck.

When working with animals, it’s important to always be aware of your surroundings, especially in the desert where I live and work. You can never be too sure that a tortoise or other wild creature is somewhere it shouldn’t be! “Check your tires!” is a common phrase around job sites and wilderness areas where you’d expect to find a desert tortoise. I’ve been working at the Desert Tortoise Conservation Center for 3 1/2 years, so checking under my vehicle for tortoises before driving away is as natural as putting on my seat belt!

A group of us had just finished a desert tortoise translocation and were driving down the road, heading back toward civilization, when my eagle eyes spotted something scurry in front of the truck. I immediately stopped to investigate and spotted a desert horned lizard sitting in the middle of road; considering these lizards blend with the desert landscape, this was an impressive find!

Pamela's eagle eyes saved the lizard from being squished.

Pamela’s eagle eyes saved the lizard from being squished.

The lizard immediately headed for one of the truck’s tires for cover. I gently moved the lizard to the shade of a nearby creosote bush and continued back to the Center.

This is a great example of why it’s important to always be alert and aware of your surroundings!

Pamela Flores is a research associate at the San Diego Zoo Desert Tortoise Conservation Center in Las Vegas, Nevada. Read her previous post, Ode to the Creosote Bush.


Desert Tortoises: Healthy Expressions

This desert tortoise is on the thin side.

This desert tortoise is on the thin side.

Compared to the numerous mammalian species you normally encounter, such as dogs and cats, desert tortoises have relatively limited means of expression. To make matters worse, they hide out in their burrows for extended periods of time and are mostly quiet. Furthermore, they can pull their legs and head back into their shell as a safety precaution when startled, so all that remains visible are their shell and the armor-like aspects of their front and hind limb scales. So, how we can tell if a tortoise is sick?

When your physician does an exam, simply asking you questions makes the task much more straightforward. Wildlife veterinarians, on the other hand, have to be much more clever and creative in using indirect measures of health. Some steps included in a routine desert tortoise health check are:

1) Activity
Is the tortoise behaving as expected? Is it alert to its surroundings? A tortoise that is letting its head hang and does not react to the examiner may be suffering from general debilitation

2) Measurements
The tortoise’s size is determined based on its shell length, using calipers. The size is an indicator of the age group of a tortoise. All desert tortoises over 20 centimeters (about 7.9 inches) are categorized as adults. It is difficult to determine the actual age of a tortoise unless you know the hatch date. The rings on the scutes of the shell are a poor indicator of age. A regular-size adult desert tortoise weighs about 5.5 to 8.8 pounds (2.5 to 4 kilograms).

3) Body condition score
This is an indicator to determine the muscle and fat mass of a tortoise. A desert tortoise with a prominent bony ridge on the top of its head is severely under condition, whereas one that cannot retract its head and limbs into its shell due to abundant subcutaneous fat stores is well over condition.

4) Shell
The shell of a tortoise is a specialized modification of skin. It contains nerves, blood vessels, and bone and is sensitive to trauma as well as metabolic derangements. The latter can be caused by an unbalanced diet and/or lack of natural sunlight or imitations thereof leading to soft and/or malformed shells.

5) Nares
The nares are inspected for exudate (runny nose) and erosions. Depending on the type and severity of the exudate, the tortoise may be suffering from an upper respiratory tract disease. Erosion around the nares indicates a more chronic disease process

6) Oral cavity
The mucous membranes of the oral cavity are examined for a healthy pink color, and the tongue is examined for presence of erosions and/or plaques. Tortoises with yellow, casseous plaques on their tongue may be suffering from a viral or bacterial infection.

7) Coelomic cavity palpation
By carefully pressing fingers into the soft skin area near the hind legs and into the shell cavity, an experienced examiner can determine whether there are masses in the coelomic cavity. Masses may include eggs or urinary bladder stones.

Why don’t we take their temperature? Tortoises, as other reptiles, are ectotherms: they do not control their body temperature as consistently as mammals but rely on environmental sources to regulate internal heating and cooling.

Identifying unhealthy tortoises is an important task at the San Diego Zoo’s Desert Tortoise Conservation Center in Las Vegas for individual animal and population health. The Center temporarily houses almost 2,000 tortoises, and each individual has to have a health check at least once a year. The goal is to release the tortoises into their native habitat, the Mojave Desert, to increase the wild population numbers. However, only healthy animals can be released to increase their chance of survival and minimize the risk of spreading disease. Unhealthy individuals are treated by San Diego Zoo Global veterinary medical staff.

Josephine Braun, D.V.M., is a scientist in San Diego Zoo Global’s Wildlife Disease Laboratories.


Tortoises: Into the Wild

Each released desert tortoise had a radio transmitter fixed to its carapace with epoxy.

Each released desert tortoise had a radio transmitter fixed to its carapace with epoxy.

It began early in the morning, before the sun peeked over the mountains. The Desert Tortoise Conservation Center (DTCC) in Las Vegas was abuzz with activity as we prepared 32 desert tortoises for the journey of a lifetime. Little did these animals know that they were about to be brought to a new home. Many of them had been living at the DTCC for several years; some had even begun their lives as pets. Now, these tortoises would be released into the wild to try to help bolster the native populations as well as give them the chance to live their lives as wild tortoises.

When the tortoises were ready, we carried each to a preset location and placed it in a sheltered spot under a shrub.

When the tortoises were ready, we carried each to a preset location and placed it in a sheltered spot under a shrub.

After placing the tortoises in hay-lined totes, we loaded them into trucks and headed to Trout Canyon, a beautiful piece of Mojave Desert habitat over the mountains to the west of Las Vegas. Once on site, the tortoises were administered fluids to help them stay hydrated in the first weeks in their new home. We double-checked the frequencies of each tortoise’s radio transmitter to ensure we would be able to track them in the field over the coming weeks and months.

We watched the tortoises for several minutes after releasing them to see how they reacted to their new environments. As you might expect, many of them were reluctant to move for a little while, but some took to walking and started exploring their new home right away!

In the four weeks that have passed since the translocation, we’ve tracked the movements of all 32 tortoises we released, as well as 20 tortoises that were already living there. Some tortoises have stayed relatively near their release sites, exploring only about one or two football fields’ worth of the new neighborhood.

Caliche caves can act as rock burrows for tortoises, protecting them from predators and the elements.

Caliche caves can act as rock burrows for tortoises, protecting them from predators and the elements.

Shelter is a prime concern for tortoises, as they need to protect themselves from extremes of temperatures (both hot and cold) and from would-be predators like coyotes or ravens. Many of the tortoises we released have found temporary shelter under shrubs like creosote or white bursage and continue to move around in a relatively small range.

A few tortoises are taking up residence in existing burrows near their release site. The burrows may be abandoned or are occupied by accommodating neighbors. When suitable unoccupied burrows are unavailable, a few industrious tortoises have begun to dig their own.

Other tortoises have taken up shelter in caliche caves. One of the tortoises found the nearest cave to its release site and stayed there for over two weeks. Then, one day, he decided to start moving and has been walking for the past few days about a third of a mile (half a kilometer) a day.

We have tracked other tortoises traversing the landscape walking miles away from their release sites. They have covered rough terrain from windy creosote flats to rocky washes and steep mountain ridges. The end of the spring growth has provided some forage for the tortoises, and they need to take advantage and gather resources now before the heat of summer dries up the best nutrient sources.

We found a desert tortoise egg just outside a burrow.

We found a desert tortoise egg just outside a burrow.

Although the race is still on for who has traveled the farthest, one tortoise in particular has certainly moved with a purpose. She scaled steep rocky ridges and deep washes only reach the top and decide to cross the next ridge to the north. After weeks of walking, she finally took a few days off to rest. Apparently she had a mission in mind, as today we found her nesting under a blackbrush on a steep mountain ridge. She had already laid one egg; we could see it just outside the burrow!

The next few weeks will be important for the tortoises as the females continue to nest and they all settle in for the heat of summer, when they will only be active in the coolest parts of the day. Finding or building burrows in the soil or rocks is very important, as is foraging. A good rain or two would help bolster their water supply for the season, but we can only wait and see what the weather brings!

Ben Jurand is a research associate at the San Diego Zoo’s Desert Tortoise Conservation Center. Read his previous post, Time for Tortoise Training.


Planning a Perfect Desert (Tortoise) Getaway

A desert tortoise is in safe hands during translocation.

A desert tortoise is in safe hands during translocation.

My boots are sitting in the hallway covered in dust. Not from lack of use, I might add. But following such an inspiring field experience in the Mojave Desert, where I released tortoises to the wild, it just seemed too soon to wipe away the dusty memories of my desert adventure.

If you work at a desk most of the time, like I do, you’ll understand that getting out into the field can be a rare and fleeting opportunity. Fortunately for me, my job takes me on walkabout to visit our field programs about once every couple of months. Each trip has a dedicated mission, from delivering vital field equipment to planning field operations alongside remotely based staff, and each trip has the added bonus of bringing me joy in connecting with the animals, people, and places where we work.

On this last trip, my trifold mission was to deliver a brand-new four-wheel drive truck to our Desert Tortoise Conservation Center, assist in a long-planned translocation of desert tortoises to the Greater Trout Canyon area just west of Las Vegas, and take staffer Julie Marshall on a memorable professional training experience. Julie works diligently overseeing our Institutional Animal Care and Use Committee, ensuring all our projects follow the highest animal welfare standards, and this trip would give her the golden opportunity to see our tortoise conservation efforts in action.

Julie Marshall radio tracks a desert tortoise.

Julie Marshall radio tracks a desert tortoise.

Our first day was spent with the staff at the Center, carefully preparing animals for their move to the wild. Each tortoise has undergone a meticulous health screening and testing over the past year to ensure its overall condition will not compromise its chances for survival. Carrying out the finishing touches, we attached radio transmitters to each of the 32 tortoises destined for freedom. The translocation effort serves two main purposes: population augmentation and research. The population of wild tortoises in the Greater Trout Canyon area has been in decline for several years. The translocated animals are expected to bolster the population and, at the very least, slow the decline in numbers. Research includes checking on the released tortoises at regular intervals to determine how they are adapting to their new environment.

Waking uncomfortably early at 4 a.m. the next day, we headed out to meet the staff, volunteers, and members of other agencies (NDOW, FWS, USGS), assisting in the translocation. After a briefing and some quick training in the use of handheld GPS units, we drove off in convoy with our precious cargo. As dawn was breaking, each tortoise received a subcutaneous injection of liquid to ensure proper hydration, and each person, carrying a tortoise in a tote, navigated to a target GPS location to make a “drop”. Fanning out across the desert landscape, our work was accomplished swiftly in the cool morning air, some tortoises remaining still until we left their sides, others trotting off into the near distance. We all left wondering, what next?

Our third and final day started just as uncomfortably early as day two and focused on finding out what next. While I caught up on center operations, Julie accompanied our field technicians to learn how to radio track tortoises. Hiking across the desert terrain following the beeping sound of an animal’s transmitter is tough work, but the payoff when you find an animal is exhilarating. After animals are translocated, they often make longer-range movements than normal in exploring their new environment, so it is key for us to follow them closely during their first few weeks of release so we don’t lose anybody.

I’m happy to report all tortoises were relocated, and I’m grateful that my job involves working with the dedicated members of the Desert Tortoise Conservation Center team who are making conservation happen and who are all infinitely better morning people than I!

Allyson Walsh is an associate director in the Applied Animal Ecology Division of the San Diego Zoo Institute for Conservation Research.


Tortoise in the Glass: Evaluating Health Problems

To you, a typical tortoise might look like this:

desert tortoise adult

But to me, a tortoise may also look like this:

desert tortoise tissue samples

I’m a veterinary pathologist, which means I spend a lot of quality time looking through a microscope at slides with tissues to try to evaluate health problems that show up as changes in those tissues. I can find dying cells, inflammation, various pathogens, scarring, thinning, thickening, bleeding, tumors, strange crystals, and unusual pigments. All of the changes help us understand the health problems affecting an animal.

At the San Diego Zoo Institute for Conservation Research, I work exclusively on tortoises that have died at the Desert Tortoise Conservation Center. Why bother? Well, it turns out that one of the best ways to figure out what health indicators most accurately indicate disease is to compare the information from the live tortoise to the changes we see in the tissues if the animal dies. The more we know about which tools work to predict severity and type of disease, the faster and more precise we are at identifying and helping animals at risk.

To get information from enough tortoises to allow good conclusions to be drawn, I need to look at a lot of slides. Since 2009, over 4,500 slides have been made of desert tortoise tissues, providing an invaluable resource for the understanding of disease in desert tortoises. Since November 2012, I’ve been describing the changes I see so that they can be correlated to what was found in the live animal. Thankfully, I haven’t been working all alone; Dr. Lily Cheng, another veterinary pathologist, volunteered to spend two whole months staring at a mountain of desert tortoise slides. Between the two of us, we’ve done more than 3,000 slides belonging to over 250 tortoises!

Are you curious about what sorts of things we see? Good! We are always on the lookout for bacteria or viruses that cause that most feared of tortoise infections: upper respiratory disease. This is more than just a head cold like people get and is a big factor in tortoise population decline. Some savvy souls may note that no light microscope can show an individual virus particle (you really need an electron microscope for that, since viruses are smaller than the wavelength of visible light). Conveniently, however, some viruses clump together to form rafts of virus particles. These are big enough to see with a microscope, just as you can see a patch of lawn even if you are too far away to pick out a single blade of grass. The virus most common and dangerous in tortoise respiratory disease (herpesvirus) forms these aggregations in the nuclei of cells, and they are called intranuclear inclusions.

Below are some cells from a tortoise that had severe upper respiratory disease. On the left side of the picture, you can see normal nuclei: round or oval purple shapes that look very speckled, like chocolate chip cookies. On the right side of the picture, the nuclei are bigger and have clumps of magenta in the center surrounded by a clear rim. They no longer resemble chocolate chip cookies at all. Those magenta blobs are viral inclusions from herpesvirus!

Herpes inclusions

The work continues at a good pace, and there are only about 1,300 slides left to look at. They weigh almost 7 kilograms (15 pounds) altogether. Wish me luck!

Kali Holder, D.V.M., is a postdoctoral associate in the Wildlife Disease Laboratories for San Diego Zoo Global.


Time for Tortoise Training

Ben prepares to take a blood sample from a desert tortoise.

Ben prepares to take a blood sample from a desert tortoise.

The Desert Tortoise Conservation Center (DTCC) in Las Vegas, Nevada, is gearing up for the spring translocation of a number of desert tortoises. We will be moving tortoises from the DTCC to a field location in the desert, where we will release them to help augment struggling wild populations.

Translocation is stressful on tortoises, because they need to adapt quickly to new surroundings, find shelter, and keep a lookout for both resources and predators. To give translocated tortoises the best chance of surviving in the wild, we need to make sure the animals are healthy and strong enough to be released. We also need to try to prevent them from spreading diseases to other tortoises in the wild.

As a new research associate at the DTCC, my first week included a lot of training. We were lucky to have several desert tortoise researchers and veterinarians visit from the U.S. Fish and Wildlife Service and San Diego Zoo Global to provide hands-on instruction on how to visually assess the health and condition of tortoises. We also learned how best to gather data and collect samples, including how to take oral and blood samples from the tortoises to test for diseases. We learned how to measure the size and weight of each tortoise, made notes about how their facial features and shells looked, and checked them for injuries or signs of illness.

DTCC staff take desert tortoise measurements.

DTCC staff take desert tortoise measurements.

Knowing their condition before we move them will help us track their progress over time in their new wild habitat. On some of the tortoises, we will be attaching radio transmitters to the upper part of their shell (called a carapace). After we have translocated the tortoises, we’ll be tracking their movements in the field and will monitor their health conditions in the days, weeks, and months ahead.

It is our hope that by continuing these studies, we will get a better understanding of how translocations affect the desert tortoises we move as well as their new tortoise neighbors.

Ben Jurand is a research associate at the San Diego Zoo’s Desert Tortoise Conservation Center.