Estimating Population Size of Maryland's Black Bears Using Hair Snaring and DNA Analysis

Wildlife Outstanding Technical Paper

Black bear (Ursus americanus) populations have expanded in Maryland since the late 1970s. Previous attempts to estimate bear numbers have been hampered by access to private land and manpower shortages. The development of hair snaring techniques, coupled with genetic fingerprinting, provides a more efficient technique than traditional mark-recapture methods to estimate black bear numbers in Western Maryland. In May-June 2000, we established 108 grids throughout occupied bear range in Garrett and western Allegany counties in western Maryland. We established hair traps in each grid for 4 week-long sampling periods. Hair samples that were snagged on barbed wires were collected after each sampling period and kept for DNA analysis. We subjected 330 hair samples to DNA analysis and identified 92 individual bears. We identified 45 males and 43 females; the gender of an additional 4 bears could not be determined. We used Program CAPTURE to estimate the bear population in western Maryland, and a total of 227 bears (95% C.I. 166-337) were estimated to occupy the 2,152 km2 area, 10.5 bears/100 km2 (95% C.I. 7.7-15.7). We found this technique to be more practical for estimating bear numbers in western Maryland than the traditional mark-recapture technique of running trap lines. Costs were substantially less per bear marked in 2000 than in previous attempts.

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