Tortoise Tales: Tracking Desert Tortoises

Lindsey poses with a desert tortoise in the Mojave Desert.

We translocated a group of desert tortoises from the San Diego Zoo’s Desert Tortoise Conservation Center (DTCC) into the wild Mojave Desert and followed them to study their movements post-release (see Spring Desert Tortoise Translocation).  My days started at 5 a.m. at the release site out in the desert. There are six separate sites that our tortoises reside in, and it was my job to locate every one of these tortoises every week. While working on this project, I saw some interesting things in the desert!

Immediately after translocation, the tortoises began to move around looking for their new homes. A small group took an especially long journey to the corner of the site, all at least a kilometer (0.6 miles) away from each other and from any other study tortoise. One resident tortoise living in this area joined our study, so we were able compare her movements as a normal wild tortoise to those of the tortoises we translocated. I nicknamed her Mrs. Rogers, because she was the only resident tortoise in a whole neighborhood of translocated tortoise friends. This site from then on was known as Mrs. Rogers’ neighborhood. In the future, we hope a male tortoise will take on the role of Mr. Rogers to help increase the population!

Lindsey uses tracking equipment to help find translocated desert tortoises.

I ran into a bit of luck one day while tracking a resident tortoise in another area. When I finally located her, I saw that she was flipped on her back, unable to right herself.  Was this due to a scuffle with another tortoise or a run-in with a predator? Because of the unique anatomy of a tortoise, death can occur if a tortoise remains on its back for an extended period of time because it is vulnerable to dehydrating and overheating if unable to seek shelter during the hottest parts of the day. I immediately righted the tortoise, wondering if I was too late. Fortunately, she walked away, seemingly unharmed.  A month after that incident, that resident tortoise is still doing great!

Sometimes, tracking tortoises can be a tricky job. Change in elevation, tortoise movement, and other obstacles make it difficult to get a good signal on our equipment. Sometimes, though, the tortoises make it easy. As I drove down the desert road, I was listening for one tortoise when I saw another study tortoise walking across my path. At first I was pretty excited, because this was one less animal I had to search for, but then I noticed he was missing his GPS unit, which we attached to him before he was released. The GPS units are only programmed to emit a signal for a certain period of time, and at that moment I only had about five minutes to locate it before the signal stopped. I quickly entered the GPS frequency and began searching for the unit. I finally found the missing unit in the mouth of a nearby burrow only a moment after the beeping stopped. The unit was recharged and reprogrammed and put back on the tortoise shortly after.

One afternoon I was tracking a group of tortoises in a wash, and I found something none of us had yet come across. There were several broken eggs in the dirt surrounding the caliche cave where one of my tortoises was living. Unfortunately, a predator attacked this clutch before hatching, but under good environmental conditions a tortoise may produce two clutches per year, so maybe next time we will see some hatchlings!

This badger was found in a desert tortoise burrow.

It is not unusual to come across a tortoise digging a soil burrow while tracking our study animals. One morning I was approaching a burrow in a wash, and I saw dirt flying out of it. As I got closer I came face to face with an American badger staring at me from the entrance of the burrow. I was getting an extremely strong signal from the burrow, indicating the tortoise that I was looking for was inside!  Badgers are carnivorous and are known to prey on tortoises, so I was concerned for the well-being of our study tortoise. I sat down several meters away to fill out my data sheet, which took several minutes.  I got up to leave and walked over to the burrow to take one last look. Our tortoise was looking right back at me! I guess the badger and tortoise are just two friends sharing a burrow.

My summer as a telemetry technician was filled with ups and downs: hiking, pulling cactus spines out of my legs, amazing wildlife, and awkward tan lines. Now, at the end of the summer, I can say the tortoises are all doing well and have somewhat settled down into homes throughout the site. They are interesting little creatures, and I hope the work we did and the data we documented will help make future projects a success!

Lindsey Perry was a seasonal research assistant at the San Diego Zoo’s Desert Tortoise Conservation Center. Thank you, Lindsey!