Twentynine Palms -- The Combat Center’s Natural Resources and Environmental Affairs division completed its second release of juvenile desert tortoises from the Tortoise Research and Captive Rearing Site March 14 through 17, 2017.
Biologists with the head start program, an initiative implemented by NREA in 2006 in partnership with University of California, Los Angeles, released 50 tortoises, who were hatched at the facility approximately nine years earlier, into the Sandhill non-live fire training area. The release of these tortoises is in no connection to desert tortoise translocation efforts that will serve as a mitigation effort in support of the National Defense Authorization Act of 2014, and is slated to take place at a later time.
TRACRS’ first release of 35 large juveniles occurred in September 2015. The tortoises released in 2015 have maintained a survival rate which is 10 percent higher than the average survival rate of tortoises raised in the wild. Biologists closely monitor each animal via Global Positioning System tracking for years after their release.
The Combat Center established the program to assess how to protect nests, hatchlings and juveniles until they grow resilient enough to endure the harsh physical environment, better fend off predation by Common Ravens and Coyotes, and mature to fully-functional adults who can produce offspring that will further bolster the population. NREA will continue with periodic releases until the remaining 390 tortoises have grown large enough to fend off predators and can be released into the wild.
“The primary factor here is that the TRACRS fencing and netting keeps out nearly all predators that would kill and eat tortoise eggs, neonates, hatchlings and small juveniles,” said Dr. Ken Nagy, research professor, UCLA. “Secondly, TRACRS is irrigated when necessary to achieve a natural rainfall regiment typical of a ‘good rainfall’ year during every year, so that food plants are available every year, on a regular seasonal schedule.”
Once the juveniles are released, they are tracked and monitored weekly via transmitted signals using directional antennas and receivers until they retreat underground for their winter dormancy period. Tracking continues during those months and picks up more frequently once the tortoises become active above ground in the warmer months.
Nagy said this monitoring will continue for many years in support of researching and supporting the recovery of the threatened Desert Tortoise species.