How Lynx Choose Dens - Rocky Mountain Research Station - RMRS

Finding a suitable home is an important challenge facing Canada lynx, a species listed in 2000 as threatened under the Endangered Species Act. But the specific type of habitat the Canada lynx prefer hasn’t been well defined, which makes managing the ecosystems that affect the lynx difficult. A new study that tracked lynx habitat behavior from 1999 to 2006 helps answer some of the questions about lynx habitat.

John Squires and other researchers at the Rocky Mountain Research Station were particularly interested in understanding whether lynx choose their habitat by the characteristics of the immediate den site, or whether the composition of the surrounding forest matters as well. They found that lynx prefer den sites with abundant woody debris, generally in mature spruce-fir forests. For forest managers, the findings suggest that thinning spruce-fir forests reduces the quality of habitat for lynx when denning.

Squires and his associates studied the denning ecology of lynx on three study areas in western Montana that represented different mixes of private, state, tribal, and Bureau of Land Management (BLM) holdings as well as areas in Lolo National Forest and Kootenai National Forest. The areas contained extensive road systems and fragmented mosaics of forest species, ages, and densities.

To conduct the study, they captured female lynx and outfitted them with telemetry collars. The lynx traps were baited with beaver carcasses and road-killed deer scented with beaver-castor lure with most lynx being captured in large box traps. They remotely monitored the lynx as they chose their den sites. After 14 days, they visited the dens to record their precise locations and determine the litter size. Even with telemetry, finding dens is often difficult because lynx often move their kittens from the natal site to a nearby maternal den within two weeks after their initial localization.

Squires and his associates studied den selection at three hierarchical scales: the den site itself (a 11.2-meter-radius circle); the den area (a 100-meter-radius circle); and the den environs (one-kilmeter-radius circle) within the female home ranges. They concluded that lynx select den sites through a hierarchical process that takes into consideration den site, den area, and den environ. Lynx select dens primarily based on the habitat structure immediately surrounding the den sites, and they typically don’t reuse den sites.

But the habitat beyond the den site has some influence on selection as well. Lynx avoided forests with thin canopy coverage, whether naturally sparse or mechanically thinned. Lynx chose dens farther from roads, but the avoidance of roads was more a function of how roads correlated to landscape patterns rather than an attempt by the lynx to avoid human disturbances.

Although the lynx appeared to have plenty of available suitable den sites, the study suggests that forest management should maintain patches of mature forest within managed landscapes. In areas that are harvested or that burn, strategies that maintain woody debris--such as leaving large-diameter logs in piles or retaining patches of dense burned forests that will wind-throw over time--will provide good future den sites. Although the threatened lynx might have other problems to contend with, finding a suitable place to raise the young ones won’t have to be one of them.