STEVE INSKEEP, Host:
Let's report next on a big cat that's making a comeback. Life for lions, tigers and other big cats has become precarious. Their numbers are declining around the world - but there's an exception in Florida, as NPR's Christopher Joyce reports.
CHRISTOPHER JOYCE: By 1995, there were maybe 25 Florida panthers left. Melody Roelke, a veterinarian who's tracked them for years, says they were a mess, with heart disease or undescended testicles.
MELODY ROELKE: The males, with even a single testis, the quality of that sperm was just abysmal.
JOYCE: They just couldn't reproduce.
ROELKE: We were actually watching extinction process right in front of our eyes. And this is what happens with small populations and inbreeding of close relatives.
JOYCE: Roelke had waded through swamps and dodged rattlesnakes to follow panthers. But this looked hopeless.
ROELKE: It was devastating. In fact, so devastating I decided to move to Africa because I had - the battle was over.
JOYCE: But a geneticist who studies big carnivores, Stephen O'Brien of the National Cancer Institute, devised a plan to save the panthers: He combined genetics and math to calculate the panther's fate.
STEPHEN O: They were going to go extinct in 25 years with a 99 percent probability if we left them alone. That's what stimulated the decision to act, to intervene.
JOYCE: So, the Texas cats came to Florida. To see if the plan was working, scientists tracked every panther and its offspring. Roelke came back from Africa - now sporting a cheetah scar on her leg - and signed on. She led teams of cat- tracking dogs into the cypress swamps.
ROELKE: They get within less than half a mile of where the cats are, and then the scent is so strong, the dogs are so excited, they just let loose and they bay and they start running. The cat then typically will run and jump up a tree.
JOYCE: A marksman would shoot the cat with a dart full of anesthetic.
ROELKE: Then we have a very brave field person who actually climbs up the tree with the cat semi-awake and puts a harness, a rope, around their chest, and then we lower them into a net.
JOYCE: Before the Texas females arrived, the Florida panthers were, well, pretty lame.
ROELKE: They would be laying there in the tree like, oh, just let me, just let me die up here, because they just lacked any kind of vigor.
JOYCE: Now, 15 years later, O'Brien says the Florida panther is a new cat.
BRIEN: I think we can say, cautiously, that it was the right decision. The population increased in number threefold. The admixture cats, which are hybrids, are much stronger and more robust and they look a little bit like Arnold Schwarzenegger version of cats.
JOYCE: Craig Packer, an ecologist at the University of Minnesota who's worked with lions in Africa, says the project is a textbook case of how dangerous inbreeding can be, even in wild animals.
CRAIG PACKER: The importance of this study is to really emphasize, not only that this population really did suffer substantial costs of inbreeding, but that it was relatively easy to resolve by bringing in a small number of new animals to the population.
JOYCE: But the Florida panthers aren't out of the woods yet. O'Brien says 100 panthers isn't quite enough to stop inbreeding altogether. On the other hand, more panthers means they will literally be out of the woods.
BRIEN: A lot of people don't want to have cougars in their backyard when they're raising their kids and their little dogs, and I think that this is a reasonable fear.
JOYCE: Christopher Joyce, NPR News.
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