DENVER — Colorado wildlife officials declared victory Friday in their 11-year effort to reintroduce lynx to the state, saying the cats are reproducing faster than they're dying, a sign of a self-sustaining population.
Colorado's native lynx died out in the early 1970s because of trapping, poisoning and development.
The state Division of Wildlife began reintroducing them in the San Juan Mountains of southwest Colorado by releasing lynx that were captured in Alaska and Canada.
By 2006, 218 lynx had been brought in, equipped with tracking devices on collars, so researchers could monitor their movements.
The first kittens born to the transplanted lynx were documented in 2003, and third-generation cats were first found in 2006.
At least 141 have been born in Colorado, including 14 this year.
No estimate is available for the state's total lynx population, partly because these animals live in remote wilderness areas. No more releases are planned.
"We put plenty of them on the ground for them to succeed," said Colorado Division of Wildlife Director Tom Remington. "They have been successful until now and we're confident that they will continue to succeed.'
The number of births varied widely, from none in 2007 and 2008 to 50 in 2005. Such wide swings are typical of lynx in Alaska and Canada. Birth rates fluctuate with the number of snowshoe hares, their primary food during the winter, researchers said.
"What we've seen from lynx in Colorado is exactly what we'd expect to see from lynx in their northern habitat," said Tanya Shenk, a retired Division of Wildlife biologist who was the lead researcher on Colorado's lynx project from 1999 to 2010.
"This supports our strong belief that the habitat in Colorado will sustain lynx over the long term," she said.
Climate change, wildfires, the bark beetle epidemic or other problems could still degrade or shrink lynx habit, researchers said.
Wildlife officials said they are shifting to a new, less-intrusive way of monitoring the lynx. Instead of capturing and collaring them, they will use other methods, such as extracting DNA from hair found in their habitat.
The program initially got off to a bumpy start after several cats starved when they were released. Officials wanted to release the cats almost as soon as they were trapped and brought to Colorado, but found that didn't work for some lynx, especially younger cats, Remington said.
They changed their methods, holding the cats in captivity for three weeks, fattening them up before releasing them in late winter and early spring, just before breeding season.
"That worked well," Remington said.
Some cats had to be brought back to Colorado after wandering into other states, including Iowa, Nebraska, Utah, and Montana.
One 9-year-old lynx that had fathered kittens in 2005 and 2006 traveled 1,200 miles back to near Nordegg, Alberta, where it got caught in a trap and died earlier this year. It was within 300 miles where it had been trapped in 2003.