Florida panthers get genetic boost from Texas : Inbreeding has weakened the Everglades natives. Cougars have been imported to halt decline.

Deep in this subtropical swamp, hidden away in a den of dense palmetto palms, TX 101 is nursing a rambunctious pair of kittens that represent the best evidence yet that the Florida panther can be saved from extinction.

TX 101 is a 2-year-old female cougar from Texas--one of eight released in Florida last spring--and the birth of her fraternal twins less than two months ago has buoyed the hopes of biologists overseeing a rare experiment to restore the vitality of the species by freshening the panthers’ gene pool.

The plan to crossbreed the endangered Florida panther with a related subspecies comes after 10 years of genetic analysis and debate, and is described as a last-ditch effort to revitalize a population of big cats riddled by health problems, including heart murmurs and sterility.

“We have a small, isolated population that has been inbreeding for 150 years, with an ever-increasing loss of genetic variation,” explained Tom Logan, chief of wildlife research for the Florida Game and Fresh Water Fish Commission. “And that’s the extinction process.”

To halt that process, scientists bet that the green-eyed females from the Lone Star State would prove irresistible to Florida males. And they bet right. When TX 101 met No. 45, the result was, bingo.

Biologists were able to find the den, and examine the kittens, by tracking the signal from a radio-transmitter collar worn by TX 101.

“In six to eight years,” Logan said, “we should have gone through a couple generations of young, and we will have restored the genetic variation that’s been lost.”

Big Cypress Swamp is a 2,400-square-mile prairie of shallow fresh water dotted by islands of slash pine and cypress trees in the northwest corner of the Everglades. Once heavily lumbered, the Big Cypress was declared a national preserve in 1974, and since then it has become a sanctuary for alligators, wading birds and wild orchids.

Although the preserve is less than an hour away from Naples, on Florida’s west coast, and less than two hours from Miami to the east, it remains one of the least accessible spots in Florida.

From the top of the food chain, the Florida panther once ruled this area, as it did woodlands throughout the South. But by 1920, habitat destruction and a legendary fear that panthers preyed on livestock and people pushed the cat into the swampy center of Florida. By the mid-1980s, the population had dropped to less than 50 animals, all south of Lake Okeechobee.

For years the future of the Florida cats was on hold while scientists and government bureaucrats debated issues of species hybridization, molecular genetics and whether or not a crossbred Florida panther would be protected by the Endangered Species Act.

Eventually, the U.S. Fish and Wildlife Service dropped its opposition to the plan after Stephen J. O’Brien, a geneticist at the National Cancer Institute, and others argued that panthers were already hybrids because historically the ranges of the Florida and Texas cats overlapped.

The aim of the South Florida panther breeding program is not to increase the animal’s numbers, which are about right for the available territory, biologists say.

Rather, the crossbreeding program is designed solely to rid the remaining Florida population of the genetic flaws resulting from inbreeding. Tests have shown that a majority of male Florida panthers have heart murmurs, undescended testicles and deformed sperm. One virus discovered in the Florida panther, O’Brien says, is a close relative of the feline version of the human AIDS virus, which attacks the immune system.

Sightings of panthers in the wild are rare. Naomi Lewis, who is postmaster of the nation’s smallest post office in Ochopee and has lived in this area all of her 60 years, said: “I saw one crossing the highway last year, but I’d have to go back to childhood to remember one before that.”

Thanks to radio telemetry, state biologists know where most of their panthers are at all times. All of the Texas animals wear the radio collars, as do many of the native Floridians. One of the eight Texas females was struck by a car and killed last month. She was pregnant with three fetuses.

Scientists figured TX 101 was pregnant and about to give birth when she stopped moving for several days after spending a lot of time with No. 45, who was radio-collared three months earlier. Her kittens were examined last month by biologists, who implanted electronic identification chips under their skin, Logan says. They will be recaptured and fitted with radio collars when they are about 8 months old, he added.

The crossbreeding program costs about $180,000 a year, and is funded entirely through the sale of specialty license plates bearing the panther’s image.

“There are still some people who think it was a mistake to introduce the Texas cougars to Florida,” O’Brien said. “But we needed to do something about this population, or lose it.”