MOJAVE DESERT: Tortoises born in captivity released into the wild
Last of 35 juvenile tortoises is let out to venture out into the big, wide world – hopefully large enough not to be a snack for a coyote.
What: Tortoise Research and Captive Rearing Site (TRACRS)
Started: 2006 with $80,000 a year from Department of Defense.
Where: Marine Corps Air Ground Combat Center, Twentynine Palms
Hatchlings: 475 tortoises have been raised at the 6-acre site.
Releases: The first 35 tortoises from the program were released over the past two weeks.
Brian Henen acts like a nervous parent, sending his teenager off in the car alone for the first time.
The ecologist has reason to be worried: A young desert tortoise that he helped raise from a hatchling is being released into the wild.
The juvenile tortoise, known simply as Two Dash Four – being the fourth offspring of adult female No. 2 – was lifted from its protective pen at the Marine Corps base in Twentynine Palms on Wednesday and placed in the open desert to make its own way.
“It’s a very important day,” said Henen, who leads the desert tortoise program at the base.
The program started in 2006 with an $80,000-a-year commitment from the Department of Defense.
The goal was to reinvigorate the desert tortoise population in the western Mojave Desert after it was nearly decimated by a respiratory virus in the late 1980s. The desert tortoise is listed as threatened under the Endangered Species Act.
In the past nine years, 475 baby desert tortoises have been raised at the 6-acre site known as the Tortoise Research and Captive Rearing Site, or TRACRS.
The compound is located at Sand Hill, in the southwest corner of the base near Landers; the area has the largest population of desert tortoises on the base.
But until this point, the slow-growing tortoises weren’t big enough to be outside their fenced compound that is covered with nets to keep out birds of prey.
There they got supplemental water from sprinklers meant to mimic rainfall and a steady diet of shrubs and wildflowers that grow naturally in their spacious pens. That helped them grow faster than they would in the wild, Henen said.
Researchers discovered in earlier efforts that releasing tortoises before they are at least 4 inches long almost ensures they will become lunch for ravens, coyotes or kit foxes.
Once they reach that size, their shells harden and they no longer risk becoming what one scientist called “walking ravioli” for predators.
Two Dash Four was the last of 35 young tortoises to venture out into the big, wide world. The others were released over the past couple of weeks.
Being larger, they also are better equipped to cope with the desert’s heat and lack of water.
“There’s all sorts of advantages to being big,” Henen said.
FINDING A BURROW
Like its mother, Two Dash Four has a small radio transmitter attached to its shell. Scientists planned to follow its movements in the hours after release to make sure Two Dash Four found a burrow.
On Wednesday, before two dozen reporters, state wildlife officials and base personnel, Two Dash Four made its way directly into a burrow surrounded by creosote bush, one of the desert tortoise’s favorite foods.
A few minutes later, the young animal was outside again, heading across the dusty, barren landscape at a surprisingly brisk clip.
That might indicate the tortoise was uncomfortable in the burrow, or it might mean it was curious about its surroundings, said Ken Nagy, a UCLA professor emeritus and lead investigator on the program.
“The burrow is critically important to their success out here because it protects them from the two main causes of death: overheating and predation,” he said.