Reptiles and Amphibians

Reptiles and Amphibians


New Generation of Rare Turtles Released into San Diego Reserve

Pond turtle releaseFive juvenile western pond turtles were released into the Sycuan Peak Ecological Reserve today by a team of federal, state and zoo scientists. The released turtles are part of the “headstart” program, which involves raising hatchlings at the San Diego Zoo to a large enough size and then releasing them into the wild, giving them a better chance of surviving and fending off natural predators.

The western pond turtles are California’s only native freshwater turtle species, a species that was once widespread in California, Oregon and Washington. They are now uncommon, especially in southern California, due to habitat loss and invasive, nonnative predators like bullfrogs and largemouth bass, which eat up the tiny hatchling turtles that are no larger than a quarter.

“Along with USGS we’re able to monitor these turtles with their radio transmitters and check on them periodically to see how they’re doing,” said Tommy Owens, senior keeper with the San Diego Zoo’s Department of Herpetology. “It’s really important here at the beginning of the release, because the turtles might not stay put and we want to be able to find them easily. Through radio tracking we can see the use of habitat, their behaviors and check on their overall well being.”

The five turtles released this morning were each fitted with a miniature radio transmitter prior to the release. Researchers attached these tiny antennae to the juvenile turtles’ shells so they can regularly check on the turtles’ growth, physical health and behavior. The transmitters were applied with a silicone sealant that allows the young turtle’s shells to grow and expand, even with the transmitter device attached to it.

Since the first generation of “headstart” turtles was released over a year ago, researchers monitoring the program have noticed progress and have been able to catch those turtles periodically to gather their measurements. After examining the turtles and checking their transmitters, researchers release them back into the same watershed.

The Sycuan Peak effort is a joint project of the U.S. Geological Survey (USGS), San Diego Zoo Global, the California Department of Fish and Wildlife (CDFW) and the San Diego Association of Governments (SANDAG). The project is testing conservation strategies to help western pond turtles and other native species, since many California ecosystems are being impacted by invasive, nonnative species accidentally or intentionally introduced by humans. The SANDAG TransNet Environmental Mitigation Program (EMP) funded the USGS’ initial work to support the restoration of the western pond turtle.

Photo taken on July 31, 2014, by Ken Bohn, San Diego Zoo.



Rare Night Lizards Form Satellite Population at San Diego Zoo

island night lizardA recently recovered endangered species, the island night lizard, has been added to the list of reptile species at the San Diego Zoo. Five night lizards arrived at the Zoo on July 25, 2014, brought by the U.S. Navy to be available for guest viewing. The species was removed from the endangered species list by the U.S. Fish and Wildlife Service on May 1, 2014.

“It is one of the few species that visitors to the Zoo will see that was recovered under the Endangered Species Act, and the only one estimated to occur in the millions on U.S. Navy Lands,” said Dr. Robert Lovich, senior natural resource specialist at Naval Facilities Engineering Command (NAVFAC) SW, Desert Integrated Product Team.

The island night lizard Xantusia riversiana is native to three federally owned Channel Islands (San Clemente, San Nicolas, and Santa Barbara) located off the Southern California coast, and a small islet (Sutil Island) located just southwest of Santa Barbara Island. San Clemente and San Nicolas islands, used by the U.S. Navy as training lands, are also home to several unique and endangered species that the naval command works to preserve.

“San Clemente Island is critical to the Navy’s ability to train and prepare sailors to fight in realistic situations. By adaptively managing wildlife like the island night lizard, we can conduct our mission requirements and remain great stewards of our natural resources. We’re pleased the San Diego Zoo has an opportunity to share this interesting creature with the public,” said Capt. Christopher E. Sund, commanding officer of Naval Base Coronado.

The island night lizard was placed on the endangered species list in 1977 because its habitat was threatened by feral goats, pigs and predators that had been introduced to the island. In 1992, the Navy removed the last of the feral goats and pigs from San Clemente Island and has an ongoing program to trap and remove feral cats and rats. In conjunction with these efforts, nonnative species of plants were removed from the island as well, greatly improving the habitat of the night lizards and promoting their recovery.

“Now that the species is recovered, it is important to ensure its ongoing survival by creating a satellite population away from its island home,” said Kim Lovich, curator of reptiles for the San Diego Zoo. “This satellite population provides insurance that the species will survive even in the event of a sudden natural disaster to its island home.”

The lizards will soon be available for viewing at the Zoo’s reptile house.

Photo taken on July 25, 2014, by Tammy Spratt, San Diego Zoo Global.



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.


Alligator Training

Xidi can be seen in the Zoo's new Reptile Walk.

Xidi can be seen in the Zoo’s new Reptile Walk.

While studying biology at the University of Massachusetts, I dedicated several years working closely with two captive, juvenile American alligators. In order for these stereotypically aggressive creatures to be utilized for classroom demonstrations, I developed a training system to make the process a little easier and, hopefully, safer! Upon my graduation, the training resulted in the alligators being able to discriminate between “attack” versus “stay” stimuli, making them a bit more predictable for the handlers.

After having a successful trial run at the University, I wanted to try similar training here at the San Diego Zoo with a female Chinese alligator named Xidi (pronounced Shee-Dee). The opportunity to begin target training on completely different alligator species is exciting! Throughout the next several months, I will be posting updates on my progression with Xidi in hopes that one day she is trained to “sit,” metaphorically, of course.

Since Xidi is a fully grown female, roughly 16 years old, I will be taking baby steps with her to challenge the cliché of not being able to teach an old dog a new trick. Previously, Xidi was fed anywhere from once a month to once a week, depending on climate conditions. Now, we will be feeding her three times a week using portion control for training progress. A dark blue circle will be used for feeding and a yellow circle for not feeding. It is unclear if alligators can discriminate colors, but they can differentiate among shades (light and dark).

Jeremy Fontaine is a keeper at the San Diego Zoo.


With a “Headstart,” Local Turtles Make a Comeback

Researchers carefully placed radio transmitters on five western pond turtles to keep track of them after release. (Photo by Ken Bohn)

Researchers carefully placed radio transmitters on five western pond turtles to keep track of them after release. (Photo by Ken Bohn)

Barely bigger than an English muffin, the dark-shelled turtle flails his webbed feet, and cranes his neck to peer at the people carefully applying epoxy to his shell. Usually a reclusive conservation celebrity, this pint-sized reptile is one of five turtles being released into a San Diego watershed to bolster wild populations of California’s only native freshwater turtle species. For western pond turtles (aka Pacific pond turtles) Emys marmorata the team of federal, state, and zoo scientists releasing the juvenile turtles into the Sycuan Peak Ecological Reserve is a much-needed effort to prevent their extinction.

Three years of collaboration between the U.S. Geological Survey (USGS), California Department of Fish and Wildlife, San Diego Association of Governments, and the San Diego Zoo are invested into this pilot project to “headstart” pond turtle youngsters and remove nonnative species from their habitat. “We have raised these turtles at the Zoo to get them large enough to avoid predation after release,” explained Thomas Owens, San Diego Zoo senior keeper. “It’s been like reverse quarantine for them. They are isolated from animals in the collection and we make sure they are handled according to protocol to ensure we will not transmit any diseases to wild populations when we release them.” With a three- and four-year “headstart,” the juveniles are no longer bite-sized morsels for other animals.

Two days before the release, staff gathered at the Reptile House at the Zoo to test and attach the radio transmitters. Clean and dry (unusual for a turtle), each turtle was weighed before the three-gram “radio pack” was attached and then weighed after it was attached. The rule of thumb is that radio packs or GPS devices should not exceed five percent of the animal’s body weight. “Large species like elephants and crocodiles, among others, have been tracked using GPS devices,” said Thomas. “But with these small turtles, which only weigh about 300 grams, it’s necessary to use tiny battery-operated devices like these radio packs. These weigh one to two percent of the turtle’s body weight.” The battery will last about three months. The antenna is carefully glued to the turtle’s scutes to not interfere with its shell growth. After much measuring and trimming of the wire, it was carefully held in place until the epoxy hardened. The first four turtles stayed safely tucked inside their shells throughout the procedure, but the last one was more rambunctious and dared to look around, urinate, and squirm in the scientist’s grasp. “The turtles all have their own personality,” said Thomas. “Some are shy and some are more assertive.” That also explains the significant size difference between them: the oldest is not the biggest, but rather a more aggressive feeder. When they hatch, the pond turtles are about the size of a quarter, so they can be easily predated by a variety of other animals. Now, at three and four years old, these guys are past the appetizer size and appear robust and healthy; they won’t go down without a fight.

Release Day

Brandon Scott (L) and Thomas Owens, reptiles keepers at the San Diego Zoo proudly hold their headstarted turtles. (Photo by the author)

Brandon Scott (L) and Thomas Owens, reptiles keepers at the San Diego Zoo proudly hold their headstarted turtles. (Photo by the author)

We met up with Thomas and two other reptile keepers, Rachel and Brandon. The five pond turtles were secured in a box with a wet towel, ready for their journey to East County. After close to an hour’s drive, the road turned dusty and wound through rustic riparian forest dotted with car-sized boulders: we entered the Sycuan Peak Ecological Reserve. Staff from our partner organizations joined us at the gate to the reserve. Another short drive and a short hike landed us at a pool with all the things a pond turtle loves: logs and granite rocks for basking, fresh, cool water for swimming, cattails and willows for shade, and plenty of insects and invertebrates to eat. Placed gently on the water’s edge, each turtle swam swiftly into the murky pond to begin its life anew.

USGS Zoologist Denise Clark released a western pond turtle. (Photo by the author)

USGS Zoologist Denise Clark released a western pond turtle. (Photo by the author)

The released turtles will be checked on daily by USGS and Zoo staff will radio track them three times a week. “Once they have established their mircrohabitat, they won’t have to be monitored so frequently,” said Thomas. Shortly before the transmitter batteries run down, scientists will catch the turtles again, give them an exam, and attach a fresh radio pack. Nonnative predators like bullfrogs and sunfish have been removed from the area to improve the turtles’ survival. “It’s exciting to partner with organizations to help restore native species to local watersheds,” said Thomas. For the mysterious western pond turtles, the project is going swimmingly!

Karyl Carmignani is a staff writer for San Diego Zoo Global.


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.


Hungry New Insectivores in Town

Researcher Frank Santana prepares to release his charges into a mountain stream.

Researcher Frank Santana prepares to release his charges into a mountain stream.

The little dotted frogs could not have picked a more picture-perfect day for their release into a remote mountain stream within their historic habitat. As wind rustles the swaying tree crowns and sunshine warms our backs, the team of multi-agency collaborators—along with a bevy of reporters—descends on Indian Creek in the San Jacinto Mountains. Bred at the San Diego Zoo Institute for Conservation Research, 65 juvenile mountain yellow-legged frogs Rana muscosa are stowed in pairs in Tupperware containers (with puncture holes) in 2 large, temperature-controlled coolers, awaiting their freedom…and a feast of fresh crickets skirting over the water’s surface. It’s an exciting milestone, years in the making.

Amphibian Adventure
In 2002, the U.S. Fish and Wildlife Service listed Southern California’s mountain yellow-legged frog (MYLF) as endangered, with fewer than 200 adult frogs scattered throughout perennial streams in the San Gabriel, San Bernardino, and San Jacinto mountains. In 2006, a group of tadpoles (once referred to as pollywogs) were collected from the wild and brought to the Zoo’s Institute for Conservation Research. Research Coordinator Frank Santana took painstaking care of little guys, monitoring tank temperature, water quality, ambient light, and everything that could possibly impact the froglets’ development.

Though there was high survivorship, breeding seemed to be at an impasse, so Frank came up with an experiment to let a subset of the frogs hibernate for 60 days in a wine chiller. This proved to be the answer to the amphibian amour riddle, as the hibernated individuals were soon mating after “waking,” with six clutches of eggs laid within two days. With the fertility issue solved, Frank was able to shift his focus to field reintroduction efforts, which culminated in the dozen people buzzing about the three release sites in the stream on June 12, 2013. By raising the tadpoles in captivity into their tailless juvenile stage (about 14 months), it is hoped that there will be less predation and higher survivorship of these animals in the wild. Driving up to the release site, Frank confides that these dappled frogs are “just as deserving of a CHP escort as the pandas.” Given the years of research and collaboration required to get to this MYLF release, I’d have to agree.

The radio telemetry "backpack" will enable researchers to keep tabs on the mountain yellow-legged frog for 30 days, when it will be removed.

The radio telemetry “backpack” will enable researchers to keep tabs on the mountain yellow-legged frog for 30 days, when it will be removed.

The Fungus Among Us
Mountain yellow-legged frogs have not graced this stream since the 1990s when the perfect storm of habitat loss and degradation, nonnative introduced trout, which eat the frogs and their eggs, and the deadly amphibian chytrid fungus sweeping the globe, conspired to destroy this species. It’s up to humans to repair MYLF habitat and safeguard against the chytrid fungus. As the road wound higher into the mountains, Frank shared with me the “extra step” taken to ensure these animals released have the best chance at survival. “We are soaking the frogs twice for 4 hours in water containing beneficial bacteria, to protect them against the chytrid fungus.” Dr. Vance T. Vredenburg, a professor at San Francisco State University, discovered that a naturally occurring strain of bacteria may help ward off the fungus in frogs. This could be a game changer for amphibian conservation!

Frank gently released 65 juvenile mountain yellow-legged frogs into the stream.

Frank gently released 65 juvenile mountain yellow-legged frogs into the stream.

Release Me
Frank and Adam Backlin from U.S. Geological Survey (USGS) crouch next to the stream with several Tupperware containers bobbing on the surface. Stream water seeps in through the air holes and the frogs seem giddy with their natural habitat so near. Other USGS staff is testing the tiny “backpacks” of radio transmitters, which will be strapped onto 15 of the frogs released. This will enable researchers to track the frogs for the next 30 days to see where they settle, and then remove the transmitters. Frank wades knee-deep into the creek and gently holds a spotted, two-inch long frog on his palm over the water. The frog pauses (for a photo?), then leaps into the water, diving deep into the blessed muck on the bottom. Frank scoops up another frog. Cameras click. The liberation process is mesmerizing. One frog hops back into his Tupperware, but quickly changes his mind. Splash! As we stand under the warm sun, the frogs begin to swim to the surface, eying their audience from their chilly element. They linger, as we do, savoring this giant leap for amphibian conservation.

THANK YOU! San Diego Zoo Global is grateful to mountain yellow-legged frog recovery collaborators at the Los Angeles Zoo, the U.S. Forest Service, U.S. Geological Survey, California Department of Fish and Game, and U.S. Fish and Wildlife Service.

Karyl Carmignani is a staff writer for San Diego Zoo Global. Read her previous post, Chillin’ Out with Cold-Blooded Creatures.


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.