DENVER -- Ten lynx kittens have been found so far during a annual spring lynx survey conducted by the Colorado Division of Wildlife.

The kittens -- seven female and three male -- were the first documented in the state since 2006.

Division of Wildlife researchers said they located five dens, including three near traditional release sites in the San Juan Mountains. Two dens were further north in Gunnison and Eagle counties.

"The discovery of kittens this year is extremely promising," said Tanya Shenk, DOW lynx field researcher. "The locations of the dens show that lynx are beginning to expand their ranges and are once again finding both food and habitat necessary for successful reproduction."

In addition, two dens housed kittens from Colorado-born parents--the first kittens documented where both parents are native to Colorado. Division biologists believe there may be additional dens and kittens not found during this year's survey.

"The number of lynx fitted with active radio collars is perhaps the lowest since we started the program," said Shenk. "We can't track all the female lynx so it is probably safe to assume there are more dens and kittens out there than what we found during our survey."

State wildlife researchers are currently monitoring 49 lynx with active radio collars. A large percentage of the original collars have stopped functioning and the vast majority of kittens born in Colorado have not been fitted with transmitters. As a result, DOW estimates of the number of kittens produced are conservative.

Division biologists speculate that a reduction in the snowshoe hare population may have contributed to a declining number of kittens surveyed in recent years. In Alaska and Canada, it is well documented that the population of lynx fluctuates with the snowshoe hare population. Limited observations by wildlife managers indicate that the hare population is down from just a few years ago.

Since the lynx reintroduction program began in 1999, a total of 218 lynx have been reintroduced. The cats were brought to Colorado from Alaska and Canada.

A total of 126 lynx kittens are known to have been born in Colorado: 16 kittens in 2003; 39 kittens in 2004; 50 kittens in 2005; 11 kittens in 2006 and 10 kittens in 2009.

While these results give a strong indication that lynx are adapting well to Colorado's mountains, DOW biologists are reluctant to say they've reached the conclusion of this project.

"We are very close to achieving all of our goals for the lynx reintroduction," said Rick Kahn, DOW lead biologist. "We have had successful breeding and we have had Colorado-born lynx reproduce. Our next goal is to determine if our level of recruitment is exceeding our mortality rates over a couple of years. We are very encouraged by the results this year and are hopeful that these animals will contribute towards a sustaining population for Colorado."

The lynx reintroduction program is funded by the DOW, private donations and Great Outdoors Colorado, which receives its funding through the Colorado State Lottery. The Colorado Wildlife Heritage Foundation has been instrumental in helping raise funds to continue lynx monitoring efforts.