Kenai Brown Bear Population


Field work for a DNA-based, mark-recapture estimate of the Kenai brown bear population on the Kenai National Wildlife Refuge and Chugach National Forest was conducted during 1 June–1 July 2010. Bears were attracted to barbed wire stations deployed in 145 9km × 9km cells systematically distributed across 10,200 km2. Using two Bell 206B helicopters and four 2-person field crews, we deployed the stations during a 6-day period and subsequently revisited these stations on five consecutive 5-day trap sessions. We collected 11,175 hair samples during the sessions from both black and brown bears, and another 91 hair samples were collected from other sources. Extracted DNA was used to identify individual bears and develop capture histories as input to mark-recapture models. Combined with data from ADFG-collared bears, at least 211 brown bears were known to be alive on the Kenai Peninsula in 2010. AIC selection of DNA-based mark-recapture models, based on 99 females and 104 males, resulted in an estimate of 428 (95% lognormal CI = 353–539) brown bears (including all age classes) on the study area. Extrapolating the density estimate of 42.0 bears per 1,000 km2 of available habitat on the study area to the Kenai Peninsula suggests a peninsula-wide population of 582 brown bears (95% lognormal CI = 469‒719).  

[NOTE: This revised estimate is slightly lower than a previously reported value of 624 brown bears. This change occurred because a recalculation of the available habitat within the sample frame increased from 9,500 kmto 10,200 km2 which decreased the density estimate and, consequently, the extrapolated estimate of the peninsula-wide population.] 

The revised full report can be downloaded below: