Large carnivores potentially change their behavior following physical capture, becoming less responsive to the attractants that resulted in their capture, which can bias population estimates where the change in behavior is not appropriately modeled. We applied occupancy models to efficiently estimate and compare detection probabilities of previously collared grizzly bears (Ursus arctos) with bears captured at DNA hair-snag sites that were not previously collared. We found that previously captured bears had lower detection probabilities, although their detection probabilities were still >0, implying that they were still visible to be sampled via the DNA hair-snag grid, which was able to detect finer differences in capture probabilities of previously collared bears compared with Huggins closed-captures population models. To obtain relatively unbiased population estimates for DNA surveys, heterogeneity caused by previous live capture should be accounted for in the population estimator.
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1 April 2008
Use of Occupancy Models to Estimate the Influence of Previous Live Captures on DNA-Based Detection Probabilities of Grizzly Bears
John Boulanger,
Gary C. White,
Michael Proctor,
Gordon Stenhouse,
Grant Machutchon,
Stefan Himmer
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Journal of Wildlife Management
Vol. 72 • No. 3
April 2008
Vol. 72 • No. 3
April 2008
DNA sampling
grizzly bear
hair snags
mark–recapture
occupancy models
program MARK