Characteristics of an Unharvested Lynx Population during a Snowshoe Hare Decline

Biologists require an understanding of the importance of untrapped areas to cyclic population fluctuations of lynx (Lynx lynx) to better manage this resource. Consequently, I examined an unharvested lynx population in the Northwest Territories, between 1989 and 1993, to determine the influence of a reduction in snowshoe hare (Lepus americanus) densities on lynx population characteristics. Lynx densities peaked at about 30/100 km2 and declined to about 3/100 km2 the winter after a decline in hare numbers. Kitten production and survival were high during peak and declining hare densities, with kittens making up 43-49% of the population. Kitten recruitment did not occur during years of low hare densities. Annual survival rates declined from about 0.90 before and during the decline in hare densities to 0.25 (P < 0.001) during the first year of low hare densities, and to 0.37 during the second year of low densities. All radio-collared lynx resident prior to or during the hare decline dispersed and/or died by the end of the first winter of low hare densities. Natural causes accounted for 1 of 4 deaths during years with high and declining hare densities, compared with 19 of 27 deaths during years with low hare abundance (P = 0.08). Most deaths from natural causes occurred during midwinter. Annual home-range size was similar between sexes (P > 0.46) and differed among years (P < 0.01); the smallest ranges occurred during declining hare numbers. Trapping pressure in the region surrounding the study area was comparatively light; only 10-12% of the estimated lynx population was harvested annually, and 19-23% of the area was > 10 km from any trapline. There was substantial natural lynx mortality during years of low hare densities. Lynx trapping during at least the first 2 winters of hare scarcity may be partly compensatory. Season restrictions may be desired to enhance the capability of lynx populations to recover once hare numbers begin to rebound.