El Centro, Calif. — Spring has arrived and things are beginning to hop - or at least crawl at a determined pace - around the Drye residence. Ravenous after a winter of hibernation, No. 6 and No. 7 thrust wrinkled necks toward any offering - a friendly scratch under the chin is nice, but a gooey banana is better. No. 7, a 22-pound, 2-foot-long desert tortoise, remembers where the best eating is and often noses through the doggie door and around the corner to the kitchen while Pat Drye cooks dinner.
As pets, Nos. 6 and 7 look like miscast anachronisms, lugging their prehistoric-era patchwork shells between lounge chairs and around the swimming pool as they get reacquainted with home. These two are the early risers, but they'll be joined soon by 18 other desert tortoises - all relocated to the backyard from a desert habitat that has become so unaccommodating to these creatures that it is believed they may go the way of their extinct ancestors.
It is people like the Dryes, not only caring for the reptiles as pets but treating them with scientific care, who may help perpetuate the species if it continues a downhill battle in the wilds. The green lawn and shaded areas of the Drye's backyard is resort living for the tortoises, whose numeric names derive from the ID numbers painted on the base of their shells.
Pat Drye's commitment to the tortoises is reflected in her comment about being offered several hundred dollars for one of her reptiles. ''To sell one is not the way you go about preserving a species,'' she says. Twenty tortoises are a lot to keep track of, but she and her family are trying to raise a whole new clutch of young born last fall. They rank a protected space in a terrarium on a kitchen cabinet.
As recently as 20 years ago, the desert tortoise was a common sight - even from cars on high-speed highways in California, Arizona, Utah, and Nevada.
But now the desert tortoise probably is easier to find in backyards than in the wild. Encroaching urban development, off-road vehicle activity, livestock grazing, continued agricultural development, and more recently, the wet weather have disrupted the tortoise's environment.
In the Mojave Desert, for example, tortoise populations averaged from 200 to 500 per square mile in the late 1800s, estimates Kristin Berry, a biologist with the US Bureau of Land Management and a recognized authority on the shelled creatures.
That original 6,000-square-mile Mojave habitat has been divided and developed , she explains, shrinking the possible tortoise habitat there to 2,300 square miles. But while the habitat has been cut by 60 percent, she estimates that 90 percent of the tortoise population in the area has been lost.
There have been some official gestures to protect the tortoise. The Endangered Species Act lists the tortoise population in southwestern Utah as ''threatened,'' but not ''endangered.'' Other populations are being considered in a status reveiw by the US Fish and Wildlife Service. In California it is illegal to take a tortoise from the wild, as was done by the truckload years ago. And all captive tortoises are required to be registered with California's fish and game department. (Slightly more than 20,000 have been registered, but Dr. Berry says that only 1 in 10 tortoises she has dealt with have been registered.)
Land preserves for tortoises - composed of government as well as private lands - are criticized because they are not continuous chunks of land, but checkerboard areas that are hard to maintain.
While the official status of the tortoise is being determined, people such as Mrs. Drye suggest that, endangered or not, the dwindling tortoise populations warrant attention before they are endangered. They don't want the tortoise - California's official state reptile - to go the way of the state's wild condor population.
The situation has given rise to several turtle and tortoise clubs - mostly tortoise owners concerned about their own pets as well as tortoises in the wild. Like Mrs. Drye, they are serious about their work, collecting data on births, development, and the best food and environment for tortoises in captivity. They also have adoption services, screening applicants almost as stringently as services for humans, says Laura Stockton of the Desert Tortoise Preserve Committee in Bakersfield, Calif. ''They make a big deal about making provisions in your will for the tortoises,'' she says, noting that tortoises typically live 80 years.