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What’s killing female desert tortoises?

  • Biologist Kristen Lalumiere removes a gopher snake from the road in Joshua Tree National Park. (Irfan Khan/Los Angeles Times/TNS) Irfan Khan

  • A desert tortoise with radio transmitters installed on his back. tns photo



Los Angeles Times
Thursday, May 18, 2017

JOSHUA TREE NATIONAL PARK, Calif. — Wildlife biologists say an alarming number of female desert tortoise carcasses found earlier this year just outside the southern edge of Joshua Tree National Park may be the result of mothers fighting extinction by exhausting their water and energy to lay eggs, even under stress.

U.S. Geological Survey biologist Jeffrey Lovich, who has monitored tortoises in and around the park for two decades, said the potentially lethal response to prolonged drought may become more common throughout the Southern California desert as temperatures rise and forage diminishes.

“This is still a hypothesis,” Lovich said on Monday, “but I believe these tortoises died after continuing to lay clutches of four eggs the size of ping pong balls year after year, using up vital resources they need to survive.”

“It was an evolutionary gamble,” he said. “If it pays off, their genetic information will be passed on to a new generation of hatchlings in conditions more suitable for survival of the species.”

A research team led by Lovich was surveying a study area of several square miles on the northern flanks of the Orocopia Mountains when it found the remains of 14 female and 3 male tortoises, and 15 live animals, most of them males.

Judging from the deterioration of the carcasses and chalkiness of the bones, Lovich concluded the animals perished over the last five to 10 years, a period including five consecutive years of drought regarded as the most severe in history.

The find has stepped up concerns over the fate of tortoises within the nearly 800,000-acre national park, which recent rains made into a showcase of habitat, lush with plants and flowers for the lumbering reptiles to fatten up on.

But vast swaths of terrain carpeted with daisies can only do so much, biologists say, in the face of longer droughts and climate change.