Young trees will help sustain snowshoe hare, primary prey for lynx, and toppled older trees may boost denning habitat
By Bob Berwyn
SUMMIT COUNTY — If there’s a silver lining to the pine beetle storm clouds sweeping Colorado forests, it may be for the threatened Canada lynx. The rare cats depend on snowshoe hares as their most important source of food, and as dead lodgepole pine forests grow back over the next few decades, they will provide vast new areas of good hare habitat, at least temporarily.
“It’s almost the best thing that could happen in terms of improving lynx habitat,” said White River National Forest biologist Wendy McGuire, explaining that the young trees will provide winter food for snowshoe hares, as well as cover for lynx. And when older, beetle-killed trees topple in the wind, they’ll provide denning habitat for lynx, right in the middle of what could be prime hunting grounds.
McGuire, who recently took over the White River slot, has been taking a close look at lynx as part of a study for the forest travel management plan. The biological assessment, as it’s formally called, was recently submitted to the U.S. Fish and Wildlife Service for a required review.
In the course of that study, the Forest Service confirmed that, even at a mature stage, lodgepole pine forests provide important cover for lynx — especially in areas with high recreational use like Vail Pass. Even dead stands of lodgepole can provide some cover for the cats as they move between areas of good habitat.
But mature lodgepole forests aren’t good for snowshoe hares, and here’s why: In winter, the hares rely on low-hanging evergreen branches for food. Since most mature lodgepoles don’t have any branches near the ground, there’s not much available for them. But when the taller trees die, the forest canopy opens. With more light reaching the ground and less competition for water and soil nutrients, the lodgepole seedlings grow quickly. In areas where lodgepoles were killed by beetles five to 10 years ago, at the start of the outbreak, the new lodgepoles are already approaching a stage of growth at which the branches will be available to hares.
Studies from Alaska and Canada show that lynx populations are tied closely to snowshoe hare population cycles, suggesting that a great abundance of snowshoe hares in emerging lodgepole pine stands could benefit lynx. Other studies in Washington show the greatest abundance of lynx and snowshoe hares in 20-year-old lodgepole pine stands that regenerated after logging, fire, or silvicultural disease.
The basic studies of lynx populations show a well-defined 10-year cycle in the northern portions of their range. coinciding with the snowshoe hare cycle. The “low population density phase” lasts 3 to 5 years. The “population increase phase” lasts approximately 3 years and is a result of high fecundity, high kitten survival, and low adult mortality. The “peak phase” lasts approximately 2 years, with little population growth. The “crash phase” occurs 1 to 2 years following the crash in the snowshoe hare population, and is due to high natural mortality, a collapse in recruitment, and increased dispersal rates.
Earlier research suggested that, in the southern portions of their ranges, snowshoe hare and Canada lynx populations are not cyclical. “This may be due to greater habitat fragmentation, resulting in lower but more stable snowshoe hare populations, and the presence of predators and competitors that do not occur in northern areas.
But those assumptions may be challenged by new research in Colorado, where biologists suspect the recent downturn in the number lynx births may be traced to a crash in the number or hares. It’s not known whether the widespread pine beetle mortality in the state has affected hare populations.
But all these factors must be considered by National Forest rangers and wildlife managers as they try to develop long-term lynx conservation and recovery strategies.
Filed under: endangered species, wildlife Tagged: | conservation, endangered species, lodgepole regeneration, lynx, pine beetles, Summit County Colorado, Summit County News, White River National Forest, wildlife