San Diego Zoo Desert Tortoise Conservation Center


Tortoise: ‘Tis the Season for Hibernation

Research associate Daniel checks tortoise hatchling pens.

As we begin the new year at the San Diego Zoo Desert Tortoise Conservation Center (DTCC), almost all the tortoises have gone down into their burrows for their winter brumation (reptilian hibernation). During the winter months, we shift our responsibilities from feeding and processing tortoises (giving health assessments to those brought in to the DTCC) to doing surveillance in our assigned areas. We walk each section of pens looking for sick or injured tortoises and for damage that needs to be repaired in the pens.

Daniel checks tortoise pens to make sure the animals are in their burrows.

At this time of year, with consistently cool weather, all the tortoises should be pretty well entrenched in their burrows. After we are comfortable that the tortoises are down for the winter, we create a wall of earth in the opening of each burrow to provide an extra layer of protection against the elements. At this point, any tortoise found outside of their burrow is cause for concern. When we find tortoises out in cool weather, we bring them in for a complete health assessment.

All sick or injured tortoises are kept in the medical center for treatment, and the tortoises that appear healthy are put back in their pen and checked more frequently to monitor any change in their condition. Typically, tortoises that are awake and out of a burrow during the cold winter months usually have a health issue causing them to come out of brumation. Doing pen surveillance is the only way we can monitor the condition of the tortoises during the winter. Since it is not healthy to disturb the tortoises in their burrows, we have to closely monitor the behavior and condition of the tortoises that are active outside their burrows.

Rachel Foster is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Saving Tortoises, One Urolith at a Time.


Rabbits, Rodents, and Tortoises

A new perimeter fence for the DTCC.

Hello again to all desert tortoise enthusiasts! It’s about that time of year for desert tortoises to begin their winter hibernation. For anyone who is new to the desert tortoise Gopherus aggaszzi, this is the time of the year when temperatures start to drop and food becomes scarce. With this seasonal change, desert tortoises begin to slow their metabolism and physical performance and search for a dark, comfortable burrow to “sleep in” through the winter until temperatures warm and food becomes more available.

Finding a secure, empty burrow in the Mojave Desert can be more difficult than just finding a hole in the ground. Desert tortoises search or create their own shelters: they may dig burrows, take another animal’s burrow, or find a small cave that protects them from the cool winters of the Mojave Desert. There are many other animals here that also are looking to hibernate or find shelter from the cold; they may cohabit a burrow with the desert tortoise through the winter season. Animals that have been known to share burrows with desert tortoises are black-tailed jackrabbits and desert cottontail rabbits as well as predators like kit foxes, coyotes, and even badgers.

Recently at the San Diego Zoo Desert Tortoise Conservation Center (DTCC), a new, reinforced fence was built to help control the movement of predacious animals onto the property. Prior to the new fence, coyotes, kit foxes, and even badgers would dig below the fence line to enter the property. This situation became a problem due to attacks on the desert tortoises and the destruction of the grounds at the DTCC. Once the new fence was built, there were no more issues with predacious animals entering, killing, or harming the tortoises.

Unfortunately, the DTCC now has a much larger problem with the local fauna. Since larger, predacious animals are not entering the property, nothing is controlling the population of smaller mammals such as rabbits and antelope ground squirrels. These animals do not directly harm the tortoises at the DTCC but harm them indirectly by scavenging the tortoises’ chow, grasses, and water we put out for the tortoises. It only shows that changing an animal’s ecosystem is not always the best answer to conserving that ecosystem.

Daniel Essary is a research associate at the San Diego Zoo’s Desert Tortoise Conservation Center. Read his previous post, Desert Tortoise: Hot, Hot, Hot.


Saving Tortoises, One Urolith at a Time

An x ray shows an adult desert tortoise with a large urolith on the left.

The tortoises have begun their fall slow-down and are preparing for their winter brumation (reptilian hibernation) here at the San Diego Zoo Desert Tortoise Conservation Center in Las Vegas. This means that the priorities in the medical center will shift a bit. We will have a few tortoises staying awake for the winter because they are either too sick or injured to brumate. However, we will also have a number of residents staying in the medical center waiting to have surgery at the state-of-the-art Harter Veterinary Medical Center, located at the San Diego Zoo Safari Park. All of these tortoises have dangerous uroliths that have developed in their bladder (uroliths are analogous to kidney and bladder stones in people).

A large stone removed from an adult tortoise carcass

Uroliths develop for various reasons, the most common being improper nutrition or prolonged dehydration. One of the adaptations that tortoises have that allows them to thrive in the arid desert environment is the ability to store large amounts of water in their bladder and to reabsorb it as the body needs it. As they reabsorb the water in their bladder, the solid particles in the bladder become more concentrated and can stick together. As time goes on more solids are deposited in the bladder and combine with those already present, forming a stone. Therefore, stones are more likely to form if a tortoise goes long periods of time without consuming fresh water to flush and replace the stored water.

Small stones that form can pass out of the bladder when the animal eliminates. However, once the stone becomes a certain size, it can be too big to pass and remains in the bladder where it can continue to get larger. If the stone is there long enough, it can adhere to the walls of the bladder, making it very difficult to surgically remove it without damaging the bladder. Eventually the stone can get large enough to take up most of the bladder space, thereby taking up very important water storage space. This compounds the problem by increasing dehydration in the tortoise. Eventually the stone can block the urethra, preventing the tortoise from eliminating at all and causing a build up of toxins in the tortoise. The long-term presence of uroliths can result in a prolonged, painful death.

A desert tortoise recovers from surgery to remove a stone.

We palpate every tortoise during its health assessment to see if we can feel a coelomic mass. Sand or gravel in the bowels or eggs can feel similar to uroliths during palpation, so we x-ray every tortoise in which we feel a mass to determine what the mass is. Once we have x-ray confirmation that it’s a urolith, we send the tortoise to the hospital, where veterinarian Nadine Lamberski has developed a less invasive technique to remove the stone. Traditionally, the most common stone removal technique used by veterinarians was to remove part of the plastron (the bottom part of the shell) to get to the stone. This procedure is very invasive and can take a very long time to heal since the bone of the plastron has to be removed. The veterinarians at the Safari Park use a technique in which they make an incision in the skin of the prefemoral area (just in front of the hindlimb) so they can access the stone and break it down and remove it without having to remove part of the shell. This surgery can take up to 6 hours to perform, but the recovery time for the tortoise is much quicker for this procedure. I am very excited to say that the veterinarians have performed a number of these surgeries successfully, and our tortoises have been able to return to us with a much better future in store for them.

We have a number of tortoises ready for surgery this winter. Once they recover, they will be able to be released to the wild Mojave Desert in the healthiest condition possible next year to live out their long lives in a natural environment.

Rachel Foster is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Desert Tortoise Hibernation: Not for All.


Desert Tortoise: Rainy Day Translocation

Pamela carefully places a desert tortoise into the Mojave Desert.

It’s 5 a.m. and a busy morning for the staff at the San Diego Zoo Desert Tortoise Conservation Center (DTCC) in Las Vegas, Nevada. We are anxious for the big day ahead, because it’s time for our fall translocation of desert tortoises back to the Mojave Desert, where they will live freely in their native habitat.

This day begins unlike most days in the Las Vegas Valley; the air is cool, and dark, ominous clouds linger over the city. As our mini-caravan of 3 vehicles, 10 people, and 72 tortoises head south on the I-15 toward the U.S. Fish & Wildlife-approved release site, we enjoy a torrential downpour of rain! The clouds are so dark, and the wind and rain are so strong, that it’s difficult to see the vehicles ahead of us. It has been a long, hot, dry summer, and we are thrilled to see the rain, but we think that perhaps this may not be the best day for hiking and releasing tortoises. But only moments later the storm passes, the skies are clear, and it’s another beautiful morning in the Mojave Desert.

The DTCC team provides fluids to a tortoise about to be released.

When we arrive at the release site, DTCC staff members administer fluids to the tortoises, ensuring they are well hydrated for their new journey. We take our time, because we want to give every tortoise the best chance of survival, and providing them with these extra fluids may carry them through a period of unexpected drought in the months to come.

Once the final tortoise is released, we take a deep breath, admire the beautiful landscape, and head back to civilization. But on the way, we discovered a wild tortoise crossing a paved road. Normally, we would watch the tortoise from a distance, ensuring its safe arrival to the other side of the road, but not this time. In the distance we see a fast-moving vehicle heading straight toward us, so we immediately jump out of our truck, and Paul, one of our seasonal research assistants, quickly but carefully moves the tortoise off the road to safety several hundred yards into the desert. What a great way to end the day; we saved a wild tortoise from possible injury or death.

The desert tortoise moments before its rescue from an oncoming vehicle.

Every translocation we conduct takes place at a release site here in southern Nevada that is approved by our partners at the U.S. Fish and Wildlife Service (USFWS), the Nevada Department of Wildlife, and the Bureau of Land Management. The San Diego Zoo is the only organization approved by USFWS to return desert tortoises to the desert; that’s because we put tortoises through a full battery of medical and behavioral tests for at least a year to ensure they are completely healthy before they leave the facility.

Pamela Flores is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Spring Desert Tortoise Translocation.


Monster Desert Tortoise

Monster is the largest desert tortoise we've ever seen!

The Pet Desert Tortoise Hotline is continuing to stay busy with lots of unwanted pet desert tortoises being turned in. Operated by staff at the San Diego Zoo’s Desert Tortoise Conservation Center (DTCC), located in Las Vegas, Nevada, we are doing pickups on a weekly basis. One big issue that we see regularly: tortoises being left behind in abandoned and foreclosed homes.

Like most areas of the country, Las Vegas’ housing market has taken a pretty big tumble, and as a result, pet desert tortoises are increasingly being left behind in vacant homes. As the Hotline assistant, I have seen many cases in which a tortoise is found by a real estate agent, landscaper, or simply a good Samaritan neighbor with a keen eye; this was the case recently with one massively large tortoise who came to the DTCC from a foreclosed home. We have affectionately named him Monster, and we think he might be the largest desert tortoise on record!

Monster was found several weeks ago by a helpful neighbor who just happened to see him in the yard. What a shock it must have been to see this huge tortoise traipsing around the yard of a home that had been empty for weeks. When I went to the home to do the pickup, I was met by the neighbor as I arrived. When I unloaded the plastic tote to transport the tortoise back to the DTCC, the neighbor, with a look of surprise, told me that the tote would definitely not be big enough for this tortoise.

In disbelief, I told her that if the tortoise would not fit in the tote, it could not be a desert tortoise; instead, I thought it had to be some other large tortoise species, such as an African sulcata, which are also popular pets here in Las Vegas. You can imagine when I walked into the yard and saw the supersized desert tortoise that I was, to say the least, a little bit surprised! How was I going to get him back to the DTCC?  With a bit of ingenuity and some great MacGyver skills, I was able to fashion a large transport carrier using both the plastic tote and a cardboard box, which delivered Monster safely to the DTCC.

Monster heads out from his enormous man-made burrow.

Since arriving at the DTCC, Monster has had his fair share of visitors! He’s been greeted by all of the staff at one time or another, and our seasonal staff members did a great job of digging him the largest burrow we’ve ever had. We can happily report that Monster is adapting well to his new surroundings, and with a little movement around his burrow, he’s always happy to come out and greet us! While Monster’s story had a happy ending, I’m reminded that for every happy ending for a lost or unwanted pet tortoise that is given up to us, there are many still stuck in the backyards of abandoned homes that we might never find out about.

I hope this might be a great reminder for folks to never leave a pet of any kind at a vacant home, even in the yard, because in most cases, the pet is not safe or comfortable, and if no one knows it’s there, it may never be rescued.

Marisa Musso is a research assistant at the San Diego Zoo’s Desert Tortoise Conservation Center.


Desert Tortoises Get Great Care

Veterinarians PK Robbins, left, and Nadine Lamberski examine a desert tortoise.

The San Diego Zoo Desert Tortoise Conservation Center (DTCC) may be located in Las Vegas, but we have constant support from the San Diego Zoo. Staff from the Zoo and San Diego Zoo Safari Park, including keepers, hospital staff, and others regularly make the trek to Las Vegas to help us whenever they can.

If you have been following us through our blog posts, you have likely read about the tortoises we receive from our Pet Desert Tortoise Hotline  (see post Tortoises Need Heat and Light), and you know that we get a number of sick and injured tortoises into our facility every week. The DTCC staff makes every effort to save these tortoises, but we but could not do this without the help of our veterinarians, Nadine Lamberski and PK Robbins, who make a trip to the DTCC several times each year. The DTCC’s veterinary technician, Rachel Foster, is in constant communication with Dr. Lamberski and Dr. Robbins, so even when the veterinarians are not physically here with us, they are always able to help and support us.

On their latest visit to the DTCC just a couple of months ago, Dr. Lamberski, Dr. Robbins, and the entire staff together evaluated a number of tortoises and discussed their health and condition in depth. This training helps DTCC staff better evaluate the health of each tortoise in our care, which is critical since we do a thorough health assessment on every tortoise that we touch. The health evaluation covers every detail on the tortoise, from the inside of the mouth to the condition of the shell. With the veterinarians’ help, the staff can easily recognize skin conditions, respiratory problems, and even learn how to feel the tortoise (palpate) for objects inside them like eggs! After the health assessment is done, the staff can decide what care needs to be provided for that individual tortoise. The DTCC and the tortoises are very fortunate to have such dedicated veterinarians and staff caring for them!

Unfortunately, there are times when we try everything possible and still cannot save the tortoise; this is the hardest part of our job. Luckily, we have Josephine Braun, a postdoctoral fellow in the Wildlife Diseases Division of the San Diego Zoo Institute for Conservation Research, who will be working closely with us for the next three years to answer questions about tortoise deaths. Any time a tortoise dies at the DTCC, we perform a necropsy (animal autopsy), which allows us and Dr. Braun to determine the cause of death. It’s like having our very own Desert Tortoise CSI!

Knowing the cause of death eases our minds, because without any information about how an animal died, we always assume we could have, should have, would have done something different for that animal, even though we don’t know what that could be. Results of the necropsies also help the staff better care for the rest of the tortoises that are on-site. Dr. Braun spends much of her time at the Safari Park, but she travels to the DTCC to stay with us for weeks at a time to train the staff in doing necropsies and fixing tissue samples. Dr. Braun also collects information from live tortoises at the DTCC to compare with her necropsy findings.

From the time a tortoise arrives at the DTCC, it is treated with the utmost care and respect. The staff goes above and beyond to save every tortoise that we care for. And because of our amazing veterinarians and postdoctoral fellow, we are constantly improving the care we give to the tortoises.

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


Tortoises Need Heat and Light

This healthy desert tortoise enjoys the warm sun.

We are reaching the mid-point of our second season here at the San Diego Zoo Desert Tortoise Conservation Center in Las Vegas, and we are seeing an increase in the number of calls to the Pet Tortoise Hotline! However, a large number of these pet tortoises arrive with a number of different health issues, most resulting from improper housing and diet. These can lead to a number of different conditions ranging from upper respiratory conditions to metabolic bone disease.

Since the entire shell of a tortoise is made up of bone and keratin, it is very important to feed them foods high in calcium to maintain the shell’s rigidity. As tortoises bask in the sun, they are not only soaking up the UV rays needed for calcium metabolism, but they are also warming themselves so that they can properly digest their food. Without the heat, even if they are eating, they are not digesting or getting the nutrients they need.

Rachel examines a tortoise at the Center.

In one case we saw this year, three tortoises were surrendered to the hotline. They had been living in an aquarium without any heat or light and were fed lettuce for several years before finally being surrendered. By the time they came to us, their condition was so severe that they were only barely alive. Their shells were flat and so soft that they bent inward with the most gentle touch. In addition, their beaks didn’t develop properly, they had severe edema all over their bodies, and they were very ill. These conditions are the direct result of nothing more than the tortoises being housed indoors and not being fed properly.

In another case, a tortoise came to us severely emaciated with old dog bite wounds all over her carapace (see a post about this problem: Family Dog Loves Pet Tortoise Too Much?). Because the family dog kept trying to use her as a chew toy, she was kept in a closet without heat or light where she was fed lettuce and fruit (not ideal for tortoises). Today, that tortoise is emaciated because, even though she was given food, she was unable to digest it without heat and light. She is just one of a number of tortoises we are rehabilitating so that some day they will be healthy enough to be released to the wild where they will contribute to the recovery of wild populations.

Rachel Foster is a research associate at the San Diego Zoo Desert Tortoise Conservation Center.


Counting Tortoises

A juvenile tortoise found a home in the remains of an adult's shell.

From March to October 2010, we are focusing on completing the tortoise inventory at the San Diego Zoo Desert Tortoise Conservation Center (DTCC) in Las Vegas, and I am happy to say that we are off to a running start! My job is to make sure we finish the inventory before the tortoises go into brumation this year, so I am supervising four seasonal research assistants (RAs) to make sure we get this challenging job done! Three of our four seasonal staff relocated to Las Vegas on June 1, and our fourth seasonal RA is a Las Vegas resident; all are eager for the opportunity to work with the desert tortoises. Little did they know they would be feeding tortoises at 5 a.m. and digging burrows at high noon in 112 degree Fahrenheit heat!

How far have we gotten with inventorying the tortoises on our 222-acre facility? We have completed the inventory of about 115 acres, but we are saving the best for last: giant 10-acre pens! While searching for tortoises in their enclosures, the seasonal RAs have made many exciting discoveries. For example, seasonal RA Holly DeAngelis found a hatchling desert tortoise under a creosote bush, a common place to find tortoises, but when the tortoise is only the size of golf ball and well camouflaged in the environment, it’s a great find by an eagle-eyed staff member!

An 18-year-resident of the DTCC!

Another seasonal RA, Paul Griese, discovered a tortoise with an ID tag indicating that it had been living on site for 18 years, almost as long as the DTCC has been in existence! It’s great to know that tortoises can thrive here in our care. Just a few days ago, seasonal RA Jason Rose discovered something we never expected to see: a juvenile desert tortoise taking shelter inside the hollow shell of an adult tortoise that died many years ago (pictured at top). On the one hand, it was sad to see the carcass of the adult, but seeing the small tortoise trucking around without a care in the world reminded us that with every generation of desert tortoise we raise at the DTCC, we have new hope that some day we can recover this species.

Pamela, far left, and the research assistants

And speaking of recovering the species: while scoping a natural burrow to see if any tortoises were in it, seasonal RA Will Lee discovered three unhatched tortoise eggs deep within the burrow! Will immediately called me, and I went out to meet him at the burrow. I gently excavated the nest and placed the eggs into a container with soft sand from the burrow for transport to our incubator. Now we are excitedly awaiting the new arrivals to the DTCC family!

There is never a dull moment here at the DTCC. As inventory of the tortoises continues to move forward, I will update you on our progress and our exciting discoveries!

Pamela Cicoria is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Tortoise Staff on Stage.


Desert Invasions

A desert fire survivor.

This spring was more beautiful than ever. Due to higher-than-average rainfall this winter, many plants and animals are thriving in the Mojave Desert, a beautiful sight to see for desert rats like staff at the San Diego Zoo Desert Tortoise Conservation Center (DTCC) in Las Vegas! Desert critters are feasting on a buffet of flowers such as the desert globemallow, which happens to be a desert tortoise favorite. We recently released healthy tortoise back into the wild, something no other organization in the state of Nevada is permitted by U.S. Fish and Wildlife Service to do, and we are confident that this release will be a huge success because of the ample forage available.

While we love to see all the native plants, this abundant bloom also presents a potential setback for the desert. Invasive plants such as brome and cheat grass are also thriving from the winter rains, and they pose a potential problem to the desert tortoise and other desert life. As summer sets in, most desert plants dry up while we are seeing invasive plants persisting all over the desert. The invasive plants can potentially catch fire from lightning strikes during late summer, causing devastation to the animals and plants of the Mojave Desert. Without these invasive plants, a lightning strike would set only one or a few native plants ablaze, but the invasive plants create a ground cover of highly flammable material that has been responsible in the recent past for fueling fires over thousands of acres of desert.

The desert after a fire.

When fire occurs in the desert, many animals can flee from the fire if they are fast enough; for the desert tortoise, however, fast is not much of an option. During a fire many desert tortoises will survive if they are in a burrow, but that doesn’t mean they are safe. After the fire is over, a tortoise comes out of a burrow to find that there is nothing to eat, which means that it must travel long distances in search of food and basically start over in finding or building a new burrow; this can cause stress on the tortoise during the extremely hot summers. The picture above is of a tortoise that survived a fire north of Las Vegas. He was tracked since the time of the fire, and I am happy to say that four and half years later he is thriving and living a fruitful life in the Mojave Desert. He was a lucky one.

Please consider xeriscaping your lawn and garden if you live in or near the desert. Strong winds blow the seeds from neighborhoods in the Las Vegas Valley out to the nearby desert, so by xeriscaping your yard, you not only have a beautiful native landscape to enjoy, but you help us protect the desert tortoise’s habitat!

Daniel Essary is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read his previous post, Watch Where You Step.


Feeding Frenzy

A desert tortoise eyes the food bucket.

They see you before you even know they’re there, waiting, watching. Gingerly stepping from pen to pen, avoiding the prickly burrs and trying not to walk into a pointed yucca while carrying a gallon bucket of tortoise chow, you feel like you’re alone out here. Sure, you know a lack of visual confirmation means they’re in the burrows, but then you get comfortable, not expecting to see anyone or anything because of the temperature of the morning. “It must be too cold,” you think to yourself, back turned as you step into the next pen, eyes cast downward, watching your step. And just as you are embracing that alone time with the desert sunrise, you look up slowly, and fast approaching on those stubby, elephantine legs, five sets of eyes have you in their sights, and they want…the food bucket!

Every morning, one of the first tasks to be done at the San Diego Zoo Desert Tortoise Conservation Center (DTCC) in Las Vegas is to round up four or five people to feed the desert tortoises that live on site. There are 6 different pen areas, all of which get fed one or two times a week by the DTCC staff to supplement the native food sources planted in their enclosures. We feed the tortoises Mazuri diet, a moistened pelleted tortoise food that has the right balance of nutrition for desert tortoises maintained in captivity.

Feeding is one of my favorite tasks at the DTCC. With tortoise season in full swing, we are collecting thousands of samples that I am responsible for banking in the lab (see Larisa’s post, New Lab Coordinator for Tortoises), so I don’t always have time to get outside. For that reason I relish the times I am able to feed the tortoises and observe them eating, walking, and just being tortoises in a natural, safe environment. Walking from pen to pen looking for a tortoise to plop a handful of food in front of reminds me very much of an Easter egg hunt: you’re not sure when or where a desert tortoise will appear, but when you find it, it’s such an exhilarating moment! You’d think by now I’d be used to seeing these tortoises, but each time is as exciting as the first for me. Granted, they’re not “excited” as much about me as they are about the bucket of food I’m carrying, but it’s still an experience I would not otherwise have were I not a member of the DTCC staff.

After giving a tortoise some chow, I sometimes take a few seconds to stand back and watch as he/she digs in, glad to be able to help do something that will, I hope, make these animals strong and healthy enough to one day be released back into the wild.

Larisa Gokool is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read a previous tortoise post, Desert Tortoise: Not Apartment-friendly Pet.

Watch a video about the DTCC…