PENS HELP SAVE BABY TORTOISES SPECIES IS THREATENED.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - Threatened with extinction by disease, predators and the activities of man, desert tortoises are getting help from the Air Force.

In an experimental program at Edwards Air Force Base, expectant mother tortoises are brought to protective pens to lay their eggs, and the baby tortoises live in the pens until they are released into the wild.

``The goal is to protect the eggs and young tortoises though their vulnerable times,'' said base biologist Mark Hagan.

He added: ``This is one tool in the toolbox. ... It's not a panacea. This is not going to save the tortoises by itself.''

Declared a threatened species in 1990, tortoises in some areas of the Mojave Desert number barely 10 percent of what they were even two decades ago, researchers say.

Areas where researchers found hundreds of tortoises in the late 1980s and early 1990s were surveyed 10 years later to find few living tortoises, but hundreds of skeletons and empty shells.

Researchers say tortoises face many threats: a deadly respiratory disease blamed on pet tortoises let loose in the desert, environmental pollutants such as lead and cadmium, off-road vehicles and Army tanks, loss of habitat to urban development and even migrant ravens that eat soft-shell babies.

At Edwards, biologists are tracking 20 adult female tortoises that live in the wild at the 301,000-acre base. Fitted with radio transmitters, the tortoises are picked up when they near their birthing season - roughly late May to early June - and are X-rayed to see if they are carrying eggs.

When eggs are detected, the creatures are brought to the pens until they lay their eggs, then they are released again back into the wild. A female tortoise can lay as many as 14 eggs, but four to seven is more typical, biologists said.

The eggs hatch around September.

Researchers are trying to determine how long to keep the young tortoises in the pens to increase their chances of survival. At 2 years old, the long-living, slow-maturing tortoise still measures only about 2 inches long.

The Edwards project, which started three years ago and is a concept used for years at the Army's Fort Irwin, will eventually keep some tortoises as long as seven years.

``It's an experiment,'' Hagan said. ``We don't have all the answers. We're learning as we go.''

Of the first eight 1-year-old tortoises released last year, only three have survived thus far. One death is believed to have been from predation.

Last year, 40 baby tortoises hatched in the pens, but only nine have survived. There are indications that ground squirrels had gotten into the pens, but it's not clear as to whether the squirrels actually killed the tortoises or if they were scavenging tortoise carcasses and eggs.

``That was devastating,'' said biologist Scott Hillard, from the University of California, Los Angeles. ``We should have had a lot of babies.''

A metal band roughly three feet off the ground now surrounds each pen to keep the squirrels away.

Researchers are also conducting an experiment in which some of the pens are being watered to encourage plant growth. The idea is to see what effect additional growth has on the development of young tortoises and whether there is any advantage toward their survival.

The project is also providing other opportunities for other research. Mark Bratton, a contractor biologist for Environmental Management, conducted a study of paternity of the egg clutches in the pens. Bratton found that in all but one of the clutches, there was multiple paternity.

Jim Skeen, [phone]

james.skeen(at)dailynews.com

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3 photos

Photo:

(1 -- 2 -- color in AV edition only) Scott Hillard, a biologist from the University of California, Los Angeles, measures a baby tortoise. In an experimental program at Edwards Air Force Base, baby tortoises live in protective pens.

(2) A tortoise equipped with a radio transmitter to track its movement emerges from its burrow.

Jim Skeen/Daily News