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.
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.
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.
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.