DENVER (AP) – Four years after lynx were introduced into Colorado’s high country the transplanted cats have produced their first offspring.

Biologists had been watching the 128 transplanted Canada lynx from the air and the ground in the San Juan Mountains of southwestern Colorado, hoping that the animals would reproduce to show the program was viable.

Four of the first five released in the state died of starvation.

On Wednesday biologists, tipped by a radio signal showing that a female was denning, found the female and two kittens at 11,000 feet on a north-facing slope, said Todd Malmsbury, spokesman for the Colorado Division of Wildlife.

“It is a big milestone,” Malmsbury said Friday. “These two are the offspring of the class of 2000.” They were born on or around May 14.

The 10-ounce kittens, their eyes still closed, are tucked into a remote den with their mother.

Wildlife biologists briefly handled the kittens to check their conditions, take hair for DNA samples and attach ear tags. The growling mother stayed close by and returned to the den after the biologists left.

Biologists think eight other female lynx may have bred this year, but this is the only confirmed cases.

Malmsbury said the confirmed births are a good start but more animals are needed. At least 45 of the animals have died since the program started in February 1999, including ten who were shot. They have been imported from Canada and Alaska.

Colorado was the southernmost point of the cat’s historic range. Trapping, poisoning and development wiped the lynx out, with the last confirmed sighting in Colorado before the recovery program in 1973 near Vail.

Opponents of the expansion of the Vail ski area set a fire that caused $12 million damage to protest the invasion of what they considered prime lynx habitat.

The lynx is protected as a threatened species under the federal Endangered Species Act. Colorado lists the lynx as endangered.

The medium-sized cats are thriving in Alaska but have significant populations in only three of the lower 48 states: Washington, Montana and Maine.