Genetic Noninvasive Capture-Recapture Techniques to Manage Polar Bears: a Pilot Study

Abstract

Global polar bear (Ursus maritimus) population numbers are expected to decline steadily over the next 50 years. A noninvasive genetic survey of polar bear numbers may be a useful addition to traditional aerial capture mark recapture (CMR) surveys undertaken throughout the Canadian polar bear population. We attempted a pilot study of noninvasive genetic survey techniques in M’Clintock Channel between May-June 2006-2009. Throughout the survey, we compared our values to the most recent (CMR) survey, conducted by Taylor et al. (2006) between March-June 1998-2000 where 133 cubs, sub-adults and adults were tagged. A total population size of 300 bears was estimated from this aerial CMR survey (Taylor et al. 2006). We found noninvasive sampling stations are sufficient for the capture of a large amount of data on individual bears in an area. Across 4 years, we collected a total of 300 hair samples, and found between 59 and 82 individual bears entered our sampling stations, depending on the stringency of our identification parameters. We estimated genotyping error from duplicated samples, and found this was low (range: 0%-6%), but large enough to not be ignored. There appeared to be a discrepancy between the capture ratio of male adult bears; the CMR survey (1998-2000) captured 25% male bears, while we estimated approximately 64% of our captured bears were male. We felt the most likely explanation of this result is that our traps have a sex bias. However, further research is required to confirm this hypothesis. On the whole, our methods are very important for the management of polar bears, but more research must be done before it can be fully implemented.