The primary prey of Canada lynx in this geographic region is snowshoe hare (Aubry et al. 2000). Nick McCann, a M.S. student at the University of Minnesota Duluth, is using a mark-recapture approach to calibrate pellet counts with snowshoe hare density. Calibration is required to convert the index of hare density provided by pellet counts from the ca. 180 transects (Figure 1) established on the Superior National Forest to an actual estimate of density. Pellet counts are conducted following the same protocol used for pellet plots. Sites that were selected fell within or near known Canada lynx use-areas. Mark-recapture efforts with live traps were conducted in February thru April 2005 at six of these sites, each site trapped 8-10 days. Captured snowshoe hares were ear-tagged and released.
It is believed that nearly all snowshoe hares utilizing each site were marked, as greater than 90% of all hares captured in the last 2 days and 100% of hares captured on the last day of trapping were recaptures. Overall, 170 individual hares were marked and released and 298 recaptures were recorded. Preliminary analysis indicates a strong relationship between pellet density and the minimum number of hares utilizing each site (Figure 2). Two additional pellet counts (Fall 2005 and Spring 2006) and 1 additional mark-recapture period (Winter 2006) are planned.
|Figure 1. Hare pellet transects. (click here to see a larger version)||Figure 2. Relationship between spring 2005 pellet counts and winter 2005 snowshoe hare population density estimates at six Superior National Forest sites.|