TWENTYNINE PALMS . (AP) — The Marine Corps is hoping to deploy some four-footed recruits in the Mojave Desert — about 500 threatened desert tortoises.

It's a serious shell game that aims to help save the species from extinction.

The hatchlings live in a special 5-acre facility at the Marine Corps Air Ground Combat Center in Twentynine Palms. The Desert Tortoise Head-Start Facility is protected from predators by wire and netting.

The $100,000-a-year program is funded by the Defense Department. It began in 2006 under a partnership between the Marine Corps and UCLA.

The slow-growing tortoises may need a year or more before they're big enough to be released into the desert.

"The program is going well, but it's taking longer than we hoped," Ken Nagy, a UCLA emeritus who oversees the hatchery program, told the Los Angeles Times (http://lat.ms/XVl4Z2 ). "These animals grow very slowly, they do everything very slowly."

The tortoise is threatened by development, off-road vehicles, disease and predators, especially ravens. Tortoise experts say that more than 90 percent of young tortoises, whose shells are soft, fail to reach maturity.

A desert tortoise census now under way at the base is expected to show a decline in the population.

However, the Marines take their survival seriously. Every Marine training at Twentynine Palms gets a video lecture about the animals, and troops are warned to halt training and notify the range master when a tortoise is spotted.

To avoid attracting ravens, Marines at the 600,000-acre base must pick up food litter and make sure that trash cans have raven-proof lids. Anti-raven pamphlets titled "Invasion of the Tortoise Snatchers" are handed out.

"If you don't start somewhere, you'll never get where you want," said Marie Cottrell, natural and cultural resources officer for the base.

Other Mojave Desert military bases also have preservation projects.

About 20 tortoises that were released from the Army's Fort Irwin carry tiny transmitters so they can be tracked.

Edwards Air Force Base hatched and released tortoises previously but they were killed by predators. A new batch will be released next year, when they are older and stronger.