The Army is seeking to move more than 1,000 Mojave Desert tortoises onto adjacent Bureau of Land Management lands to make way for expanded training operations at California's Fort Irwin, despite the loss of many tortoises that were relocated last year.

The fort's resident tortoises, which are listed as threatened under the Endangered Species Act, would be relocated to BLM lands south and west of the training base, as well as to other Army lands purchased to provide habitat for tortoises. The new round of relocations would allow the Army to use about 94,000 additional acres for training.

But about 90 of 600 tortoises moved last year died in their new habitat, primarily from coyote predation, prompting the Army and BLM to temporarily suspend the $8.7 million translocation program.

The Army has proposed to move more than 1,000 threatened desert tortoises from Fort Irwin, in California's Mojave Desert, to make room for additional training grounds. Photo courtesy of the National Park Service.

Ileene Anderson, a biologist with the Center for Biological Diversity, said the Army and BLM should hold off on relocating additional tortoises until they can provide greater certainty that the animals will survive.

"I would have thought that the Army and BLM would have made some provision to limit coyote access to the desert tortoise habitat," Anderson said. "It appears that the feds aren't really interested in the actual success of the translocation if they fail to address the documented issue that caused the primary failure in the initial translocation."

Studies done as recently as 2004 and 2005 suggest that desert tortoise populations continue to decline, particularly in the western portion of their range. The tortoise's remaining habitat is concentrated in desert regions of Arizona, Southern California, southern Nevada and southwestern Utah (Land Letter, Feb. 12).

A BLM environmental assessment of the Army's new translocation proposal, issued July 31, concluded there was not much difference in predation levels between the relocated tortoise population and the fort's resident population.

"Analysis of the ... data indicates that translocated tortoises were not preyed upon differently from resident tortoises," the assessment states. High predation rates also occurred in wild tortoise populations throughout the Mojave Desert, BLM added. "Therefore, it is generally concluded that the rates of predation associated with the initial ... translocation was within natural levels."

The higher tortoise predation levels may be related to drought, which scientists believe may have reduced the population of rabbits, coyotes' typical prey base, forcing them to rely more heavily on tortoises for sustenance, according to BLM. Researchers plan to monitor about 20 percent of the translocated tortoises over the next five years, according to the assessment.

Predator control is not an option at the translocation sites because studies have not demonstrated that it is effective, BLM said, adding that if predation continues to be an issue, "additional strategies may be developed" to deal with the problem.

Data questions

Chris Otahal, a wildlife biologist with BLM's field office in Barstow, Calif., said new information submitted during the current public review period casts doubt on whether more tortoises can be successfully moved from the fort onto BLM lands.

Specifically, he said, there remain "some serious questions" about the reliability of the data in the study that concluded predation rates were virtually the same for both translocated tortoises and those still inhabiting their native habitat at the fort. "Obviously, that's a major concern," Otahal said. "Now we're finding out the data we've been basing a lot of our analysis on may have some issues."

The U.S. Geological Survey, which conducted the study in question, is re-evaluating its data, he added.

Given the new uncertainty about the USGS data that BLM relied on to conclude that predation was not greater in translocation sites, and therefore not a major concern in the new translocation proposal, BLM could suggest delaying the effort.

"Obviously, we, BLM, want to make sure we base our decision on the best data," Otahal said.

That would likely be unwelcome news for the Army, which hopes to begin moving the tortoises as soon as next month. Tortoises can only be moved in the fall or spring.

John Wagstaffe, a spokesman for Fort Irwin, said the Army wants the translocation effort to be successful. "We're not going to do it if we're going to kill them," he said. "It would be crazy after all the time and money we put into the tortoises to relocate them only for them to die."

BLM will issue a determination on the environmental assessment Monday, Otahal said. The 15-day public comment period, abbreviated to accommodate the Army's request for an accelerated timeframe, ends tomorrow.

Click here to read the environmental assessment.

April Reese writes from Santa Fe, N.M.