BrightSource Energy Establishes “Head-Start” Program for Desert Tortoise
As a part of BrightSource Energy’s extensive desert tortoise protection program, the company has established a “head-start” program at the Ivanpah project site. Head start programs are a critical avenue for enhancing repopulation of the desert tortoise – a federally listed “threatened” species. In their natural environment, less than ten percent of juvenile desert tortoises survive beyond five years of age due to predation from ravens, kit foxes, and coyotes and other factors such as drought and disease.
“One of the biggest challenges facing the desert tortoise population is the high mortality rates for juveniles. Head-starting in areas where tortoises have been depleted for other reasons is a significant step in the right direction,” says Mercy Vaughn, the lead biologist for the Ivanpah project. “The project is leading the way for private industry serving as a proactive model in conservation of the threatened desert tortoise.”
In addition to moving the desert tortoise out of harm’s way, the head-start program is enabling tortoises to be hatched within a protected area, watched over to ensure they are more likely to survive, and ultimately released into its natural environment to further repopulate. The Ivanpah program will provide desert tortoise biologists with important information about head-starting and its effectiveness in repopulating the desert tortoises.
Late spring and early summer is prime egg-laying season for egg-bearing (“gravid” in tortoise biology terms) female tortoises. In the new head-start facility, the egg-bearing females found on the project site will be placed in special hatchery pens until eggs are laid. To date, 23 gravid tortoises have been placed in the Ivanpah pens and are being monitored daily to assess if eggs have been laid. After the eggs are laid the females are moved to different pens to ensure that the eggs are not inadvertently damaged by the female tortoise. (Unlike some other species, once the desert tortoise female lays her eggs, they do not take any further care of their offspring in the wild.)
The eggs will incubate for approximately 90 days, and upon hatching, the neonates (newly hatched tortoise) generally use a rodent burrow for hibernation until the following spring. Egg-bearing female tortoises generally lay 4 to 8 eggs each season. The newly hatched juveniles will be protected from predators, fed, watered, and monitored daily by trained biologists following a detailed tortoise care plan. Once they grow large enough to be less vulnerable to predation, the tortoises will be reintroduced to the wild.
This summer, biologists working with BrightSource will build a series of highly secure, specialized juvenile tortoise pens to care for and protect the hatchlings. The pens will be carefully protected from predators – which include ravens, raptors, ground squirrels, foxes and coyotes – by special mesh security fencing. The fencing will be buried about a foot below ground to prevent predators from burrowing into the pens. Juvenile tortoises also require special habitat considerations because they may not be able to dig through rocky terrain. Biologists will identify a location that is most suitable for juveniles in terms of vegetation, topography and soil.
There are currently a small number of head start programs for tortoise, including programs at Ft. Irwin National Training Center, Edwards Air Force Base, Twenty-nine Palms Marine Corps Base, Mojave National Preserve and others. Biologists are hopeful that future and ongoing desert tortoise head start programs can share information and findings to maximize the success of each facility and aid in the recovery of this important species.