Gustavus Forelands Bear Population Study

Brown bear approaches a scented hair trap.

NPS

 

Black and brown bears provide important wildlife viewing opportunities within Glacier Bay National Park, and sport hunting opportunities in areas near the park, such as Gustavus and in the Preserve at Dry Bay. During 2011 and 2012 Glacier Bay National Park and Preserve and ADF&G collaborated on a study to assess the bear population in a 200 km study area of the Gustavus Forelands using genetic analysis of bear hair from bear rub trees (and scented hair traps). Map of Study Area

Wildlife managers often rely on population estimations to guide decisions on harvest levels of game species. Many game animals regularly cross federal and state jurisdictions, creating a shared interest in population data across multiple agencies, which pertains to the black bear in northern Southeast Alaska. Until this project, there had been no regional population studies on this species despite management goals of 10% harvest rates. Over the course of the study, researchers collected 196 hair samples from 25 rub trees and eight baited hair traps, and identified 33 individual black bears and 14 individual brown bears. Pinjuv (2013) estimated that the likely population of black bears in this region to be 54.5 ± 10.3 individuals (estimate ± SE). The average number of black bears killed by humans annually from 1990 through 2011 was 3.68 individuals, indicating that the level of harvest during the study was within the 10% allowable take. Continued monitoring of population and harvest rates is encouraged to allow state and federal wildlife managers to ensure black bear harvest and viewing opportunities into the future.

The number of individual brown bears identified in the Gustavus Forelands was surprising because they had rarely been seen and have only recently begun using the area after a 50 year absence, providing further evidence of brown bears’ recent range expansion as documented by Lewis (2012). Information from this study and others has led to increased community outreach regarding brown bear behavior and safety in the town of Gustavus.

Lewis TM (2012) Shoreline distribution and landscape genetics of bears in a recently deglaciated fjord: Glacier Bay, Alaska. MS Thesis, University of Alaska Fairbanks, Fairbanks, Alaska.
Pinjuv K (2013) Estimating black bear population size in Gustavus, Alaska: implications for determining the effect of human caused mortality on population size. MS Thesis, Evergreen State College, Olympia, WA.

 

Do Bears Shed in the Woods? Find out how we collect bear hair for analysis.

Bears rub on trees repeatedly over time, often along regularly used bear trails. The trees are identified by claw and bite marks. Bear rub trees in the study area were equipped with two small strands of barbed wire so when bears rub on the trees they leave clumps of hair on the barbs. Additionally, eight scented hair traps were deployed throughout the study area. These are enclosures of a single strand of barbed wire placed in proximity of regularly used bear corridors. In the center of these enclosures there is pile of rotten wood with a smelly attractant on it, such as a mixture of rotten cow's blood, fish fertilizer, and glycerin. The bears slip underneath the barbed wire, depositing hair on the individual barbs. Motion sensor cameras placed overlooking some of the traps suggest that bears spend very little time investigating once they determine that there is no actual food reward.

 

Check out the bears on film!.
See what our hidden cameras discovered near Gustavus

 

The hair samples are sent to a lab for genetic testing. These tests provide information on individual id, species, sex, and potential genetic relatedness of other bears beyond the study area. Mark-recapture analysis will be done when the genetic tests are complete. A "mark" occurs when we obtain the first sample of an individual bear. "Recapture" occurs when we obtain hair from that same bear during another sampling session. Statistical analysis will be done to inform the probability of marking new individuals and recapturing marked individuals. The results from this analysis will give us a minimum number and an estimated population of bears using the Gustavus Forelands.

 

Read more about this project.

Project Poster
Gustavus Forelands Bear Population Study