October 25, 2006

SIGNS OF SUCCESS IN FERRET POPULATION

Biologists sweeping spotlights across the sage hills of northwestern Colorado recently spotted two pairs of green, gleaming pupils that mark a turning point in the state’s black-footed ferret program.

The eyes belonged to two ferrets born in the wild.

Since 2001, federal and state biologists have introduced more than 200 of the prairie predators to two areas near Dinosaur National Monument.

The ferrets are thought to be the rarest mammal in North America. In 1985, after decades of disease and habitat eradication, only 18 ferrets remained. A massive recovery effort, including captive breeding at Cheyenne Mountain

Zoo and six other facilities, and release into the wild in six states, has brought the population up to about 1,000.

Most of the ferrets released in Colorado have died in less than a year.

“Chances were slim to none any would make it more than a couple months,” said Rick Krueger, a wildlife biologist for the U.S. Fish and Wildlife Service.

Then last fall, searchers using powerful flashlights to spot the nocturnal hunters in the field documented a yearling female who wasn’t like the 12 other ferrets they saw.

Captive-bred ferrets have two computer chips, each the size of a rice grain, under their skin. Biologists use a ring placed over a den entrance to read the chip as a ferret exits.

The young female had no chip.

It could have been a fluke, Krueger said. “As unlikely as it is, both chips could have come out.” But researchers were hopeful.

Then, in September, they collared two more chipless youngsters.

“It was great news,” Krueger said. “The wild-born critters are smarter, more able to survive, more able to hunt.”

He has observed different reintroduction efforts from lynx to wolves to Colorado squaw fish. “It’s not unusual early on to see 100 percent mortality in reintroduction efforts. Then, suddenly, for whatever reason, a wild-born population gains a foothold and takes off.”

It can’t come too soon.

In recent years, the U.S. Fish and Wildlife Service, which oversees the annual distribution of captive-bred ferrets across the West, cut back the number of ferrets reintroduced in Colorado.

“We’re certainly not giving up on Colorado, but we haven’t been giving the state a large allocation because of the problems,” said Mike Lockhart, who heads the National Black-Footed Ferret Conservation Center north of Fort Collins.

He called the wild-born ferrets in Colorado “very encouraging news.”

“Once they’re established, the wild ferrets can be very resilient,” he said. “We have sites in Wyoming that we all but gave up on because of disease. We stopped releasing ferrets there. But the ones that survived reproduced. Now it’s growing by leaps and bounds. Ultimately, what we want is self-sustaining populations. This is a big step in the right direction.”

Tuesday, biologists released 10 more captive-bred ferrets on the Colorado release site, for a total of 25 this year. Lockhart said the good news may lead to more ferrets being released in the state next year.

“Seeing wild-born kits is a major milestone,” said Della Garelle, the zoo’s conservation director. “It shows the animals we’re breeding are healthy enough to survive and reproduce out there.”

The zoo has 12 kits scheduled to ship out Thursday. Some will go to other captive breeding centers. Some will be released on the land, where wild mates can show them how to breed the old-fashioned way.