The U.S. Marine Corps has announced a plan to fly more than 1,100 endangered desert tortoises away from their habitat in California to make way for a new training ground, but conservationists aren’t happy about it.

The move, they say, could result in hundreds of tortoise deaths.

The plan is to translocate the animals from the Johnson Valley Shared Use Area—which is about to become a part-time military training ground—to nearby terrain where they won’t be crushed by military equipment.

Ileene Anderson, senior scientist with the Center for Biological Diversity, worries the move could put this batch of animals at higher risk of death from predators, disease, and other environmental obstacles.

The fears aren’t unfounded. Back in 2008, the Army moved about 770 desert tortoises from areas around California’s Fort Irwin, and a large number of them were killed by coyotes almost immediately after arriving in their new habitat. At least 120 more died from unknown causes.

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Desert tortoises are basically homebodies, Anderson explained. They can live to be 80 or 90 and spend most of that time within very small ranges.

“Once they’re old enough to survive and be out there on the landscape they settle down on the territory,” Anderson said.

Each tortoise digs four to eight burrows, in which they spend the majority of their lives when they aren’t looking for food. Not only do the burrows protect them from predators, but the consistent underground temperatures also keep them safe from the desert’s scorching sun and cold nights.

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Moving tortoises away from their burrows creates problems.

“They don’t know where they are,” Anderson said. “They don’t know where there are any escape burrows. They’re on the surface for so much longer, so if it’s particularly hot or particularly cold, then, being reptiles, they can be exposed to environmental conditions.”

Some tortoises monitored in other relocation efforts died because they tried to find their old burrows. “The tortoises that have been translocated have this incredible capacity for homing back to their home territory,” Anderson said. “They can travel six or seven miles and have been successful at that, and one of them traveled up to 15 miles to make it back to his home territory.” That, too, leaves them exposed on the surface for dangerously long periods of time.

But the threat of disease may be the most pressing issue. An upper respiratory tract disease has made its way into wild tortoise populations, most likely owing to humans releasing captive animals back into the wild.

“It’s like pneumonia for tortoises,” Anderson said. “There have been examples where there have been translocations and there has been a disease breakout in that resident population.”

The U.S. Fish and Wildlife Service, which administers the Endangered Species Act, signed off on the Marine Corps’ plan back in 2012, but no translocation plan has been made public.

“I’ve been checking in every day for the translocation plan,” Anderson said. She wants to know where the tortoises will be moved, and to ensure that the plan reflects scientific information about translocations that has been learned since the disastrous attempts at Fort Irwin.

The Marine Corps did not respond to TakePart’s request for comment, but a spokesperson told the Hi-Desert Star that the relocated tortoises would be monitored for 30 years, at a cost of $50 million.

The Center for Biological Diversity has notified the Marine Corps that it intends to sue to block the translocation. That lawsuit could move forward in 60 days. Meanwhile, the tortoises may not have much time. The Marine Corps plans to start training exercises on Aug. 1.