26 Jul New San Diego Zoo program to offer threatened California Desert Tortoises a head start
Spartacus moves slowly, but with determination. The male California Desert Tortoise is not a big fan of the heat, and if it were up to him Spartacus would probably be hiding from the morning sun a few feet underground in a cool burrow of his own making.
A resident of The Living Desert zoo in Palm Desert, Spartacus is used to the finer things in life, like fresh lettuce leaves and the occasional hand-picked prickly pear. For his relatives in the wild, life has grown increasingly difficult. The California state reptile has been threatened by human disturbance, development and predation, causing a steep decline in native populations.
San Diego Zoo Global, the international conservation organization that operates the city’s famous animal park, has recently kicked of a program providing a safe environment for tortoise hatchlings before releasing them into their natural habitat, where they will continue to be monitored for research.
Referred to as “headstarting” programs by experts, initiatives like this provide an environment for the small tortoises to mature out of the hatchling phase, during which they’re the most threatened by predators. Just about 2 percent of tortoises survive this phase of their lives, according to a news release by Cadiz Inc, one of the zoo’s partners on the project.
While predators have always posed a threat to tortoise hatchlings, human encroachment on tortoise habitats has improved conditions for predators, such as ravens.
“Ravens are a natural component of the Mojave Desert ecosystem,” Sarah Greely, desert tortoise conservation coordinator at The Living Desert, explained. “The problem is that because humans have moved into the Mojave Desert — because we also like the desert — we have inadvertently provided subsidies.”
Enjoying the artificial moisture of watered lawns, the comfortable seating and nesting opportunities provided by roadside billboards and trash cans full of leftover treats to scavenge, ravens have been able to thrive in the desert. “As they’re seeking out food, they learn new sources and one of them happens to be desert tortoise hatchlings,” Greely said.
To help protect the local tortoise population, Greely and her team are urging local businesses to lock their trash cans to reduce food sources for ravens, and keep populations at bay.
In addition, Greely said, desert residents should refrain from “rescuing” desert tortoises they find in the wild, or releasing pet tortoises in the desert. “Keep your wild tortoises wild, and the captive tortoises captive,” Greely said. Once they’ve spent time in captivity, tortoises can carry diseases that will kill their desert-dwelling relatives.
Aside from known predators and fatal diseases, there has been limited research on the factors at play in the desert tortoises’ demise, especially in the early stages of an animal’s life.
“It’s an understudied life stage, because they’re so hard to find in the wild,” said Lisa Nordstrom, associate director of recovery ecology at the San Diego Zoo Institute for Conservation Research. Before their release, every juvenile will be fashioned with a radio transmitter to monitor their progress in the wild.
By tracking juvenile tortoises, researchers hope to gain more information about the relationship between habitat characteristics and survival chances, the threat levels faced by juvenile tortoises of different age groups and a number of other factors that may have an impact on tortoises’ chances of survival.
The project will nurse two separate tortoise cohorts, the first of which is expected to hatch soon. The second will join the program as eggs in early 2019. Both will be released simultaneously in early 2020. By releasing juvenile tortoises of two different age groups into their natural habitats in the Mojave and Colorado deserts, researchers hope to learn more about their individual survival chances in each environment.
“We’re really hoping to gain a lot of different information from this single study,” Nordstrom said. “We really need a lot more information to create a successful program and be able to increase those populations.”
Cadiz Inc., a publicly held utility company with land holdings in eastern San Bernardino County, provided crucial resources to the project by providing funds and land for the project’s new headstarting facility in a critical desert tortoise habitat.
“It’s a master plan of a resort for the desert tortoise,” said Tim Shaheen, the utility’s chief financial officer. “It’s very exciting to be part of a project to save a species from extinction.”
But saving the desert tortoise goes beyond the survival of just one species. Nordstrom said. “Desert tortoises really play a key role in the ecosystem,” the conservation specialist explained. “In an area where desert tortoises are blinking out, that might be a sign that the desert ecosystem as a whole isn’t doing as well.”
After all, desert tortoises have been roaming the desert for much longer than its human residents. “They’ve been around for millions of years, and we hope to keep them around for longer,” Nordstrom said.