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Colorado’s lynx are feeding, but not breeding

Article by Allen Best

Wildlife – February 2002 – Colorado Central Magazine

NEARLY THREE YEARS since the first of 96 Canada lynx were transplanted into Colorado, survival of the species here remains in doubt.

It’s not for lack of food. Unlike February 1999, when four of the first five lynx released into the San Juan Mountains died of starvation, wildlife researchers are confident that lynx have found enough to eat. Some have even been caching kills, to eat later.

But unless the lynx start reproducing, it’s likely that the lynx will disappear from Colorado, one by one, just as the native population that preceded them. To date, wildlife researchers have found no signs of lynx kittens resulting from the 44 lynx — 24 female and 18 males — still known to survive. Twelve more are unaccounted for, and hence may be alive or dead.

“We hope to see some little tracks along with the bigger tracks this winter,” said Todd Malmsbury, spokesman for the Colorado Division of Wildlife, which transplanted the lynx from Canada and Alaska. “But we saw nothing this summer to suggest there are small lynx out there.”

A few lynx have been roaming along Interstate 70, but most remain in, or have returned to, the San Juan Mountains. Even so, that’s a broad sweep of chaotic geography, and the chance that one of the 18 males will encounter a female in heat appears to be rather slim. Unlike some species, male and female lynx do not pair for extended periods or for life.

Instead, they breed in March, and go their separate ways. Gestation takes about nine weeks, resulting in a litter of one to six (three is typical) kittens to be raised by their mother. The youngsters generally disperse in the fall, although occasionally they stay through the winter.

Additional transplants would boost the odds of lynx mating, and hence a self-sustaining population. However, that idea is caught in a Catch-22. To justify more transplants, state authorities first want to see evidence that reintroduction is working.

“It is difficult to reintroduce species, and it is also very expensive,” explains Malmsbury. “And it certainly would be more difficult to justify going forward with reintroduction given there are other priorities. This is not the only species we are worried about or need to pay attention to.”

Re-establishing a population was never certain in the program, Malmsbury added. “We hoped it would occur, but we never assumed that it would.”

So far, $1 million has been spent. The money came from donations by the Turner Foundation, media mogul Ted Turner’s philanthropic organization; Great Outdoors Colorado, which dispenses lottery proceeds; Vail Associates, operator of Vail and Beaver Creek; and from hunting licenses.

One of the largest costs has been to pay trappers to capture the lynx in Canada and Alaska. It was expensive before, when lynx there were at population peaks, and the cost would escalate now that lynx populations have crashed, part of a 12-year cycle that has been documented since the 1830s.

HOWEVER, SOME BIOLOGISTS warn that Colorado may be preparing to draw the wrong conclusions. More animals are vital, they say, to ensure reproduction.

“If we don’t get reproduction, we could come to the wrong conclusion that indeed, lynx cannot survive as a viable population in Colorado, when in fact we might have only had too few of them out there,” says Tanya Shenk, a Fort Collins-based mammalian researcher for the state wildlife agency.

Durango-based Scott Wait, a terrestrial biologist, warily points out that the decision belongs not to wildlife biologists, but to the Colorado Wildlife Commission, which sets wildlife policy, and to its parent agency, the Department of Natural Resources.

“I cannot make the policy whether (more transplants) are necessary or whether we accept the position that lynx are no longer capable of living in Colorado,” says Wait.

Gene Byrne, a Glenwood Springs-based terrestrial biologist who helped engineer the original releases, says that from the outset, wildlife biologists were dubious that 100 transplanted animals would be enough to create a self-sustaining population. “It’s a numbers game, and more is better,” he says.

Rich Reading, a conservation biologist affiliated with the Denver Zoo and the University of Denver, says his study of hundreds of wildlife reintroductions in several countries suggests four or five years of transplants will be needed to ensure a reproducing population.

“That seems to be a threshold,” he says. “If you don’t do four or five years, most reintroductions fail, and it has a lot to do with something called the Allee Effect.”

THE ALLEE EFFECT, he went on to explain, is named after the researcher who articulated the phenomenon. Simply put, reproduction is difficult simply because there are too few of the animals for them to find one another, especially during the narrow period of time when females are receptive to male advances.

Lynx are solitary creatures anyway. So the probability is low that one of the dozen or so males in the San Juans will find a female during her narrow window of receptivity.

Reproduction may also be affected by the tendency of species, when recolonizing areas, to be slow to reproduce. It could be because of suboptimal habitat, or perhaps because of hesitancy about new terrain.

“It would be a shame not to see this project through to its completion, because I think it can succeed,” adds Reading, who co-chairs the lynx advisory team.

If frustrated by the lack of reproduction, however, wildlife researchers have already learned much. “We have basically been writing the textbook about lynx in the Southern Rocky Mountains ecosystem, and to an extent in the lower 48 states,” says Malmsbury. “There wasn’t that much known about them.”

First, it appears the prey base for lynx is at least adequate. They’re finding snowshoe hare, their primary prey, and sometimes stashing the uneaten portions of their kills. A five-month survey last winter by ground crews located 88 kill sites: two-thirds were snowshoe hares, the remainder mostly red squirrels and cottontails.

This count suggests that lynx in Colorado will be less dependent upon snowshoe hare populations than lynx in Canada and Alaska, where hare comprise up to 90% of lynx diets. Biologists had predicted this.

However, biologists had not predicted all the ways that lynx could die.

First, there were lynx starving soon after being released. After that flurry of deaths among the first transplants in February 1999, animal activists called for a summary end to the transplanting. However, wildlife researchers instead refined their procedures, confining lynx for three weeks while feeding them rich diets before finally releasing them. With that change, few died quickly of starvation.

Altogether, 9 have died of starvation, 10 of unknown causes that may have included starvation, and 4 died of unknown causes that didn’t include starvation.

Five have died on highways, including two along Interstate 70, two more in the San Juans, and one in New Mexico. This mortality came as no surprise.

Another five have been shot to death, including one killed by a sheepherder who said the lynx had been attacking one of the sheep under his guard.

The only real surprise has been the death of three lynx because of plague. “That is something we had not anticipated, and it could be a significant factor,” says Malmsbury.

So far, there appear to be no clear conclusions about whether Colorado’s habitat works well for lynx. With its profusion of timberline-piercing mountains and broad valleys, the Southern Rockies are naturally far more patchy than the vast stretches of pine forests in Canada and Alaska.

And Colorado’s patchy habitat has been made even more patchy by the maze of highways.

Wildlife researchers are unready to draw conclusions about compatibility of lynx with ski areas, which occupy the same band of forest terrain — 8,500 feet up to timberline — favored by lynx.

Ski area managers want to believe that lynx and ski areas are compatible. They have eagerly publicized sightings of transplanted lynx, first at Keystone in 1999 and then at Telluride in 2001.

However, wildlife biologists aren’t yet ready to draw conclusions. “We are just now studying the data,” says Wait from his Durango office. “We have no strong management recommendations on that one way or another.”

If those recommendations are rendered, they will strongly influence where ski areas can expand and, in a few cases, if new ski areas can be created.

Allen Best has been known to ski when he isn’t writing about lynx. He lives on the Interstate 70 Sacrufuce Zone, with terminals at Arvada and Glenwood Springs.