Biological Projects

Kuskokwim MountainBrown Bear Study:

In 1991 and 1992, State and Federal regulatory boards significantly liberalized brown bear subsistence hunting within the Western Alaska Brown Bear Management Area (WABBMA). This area includes the Yukon-Kuskokwim Delta, the Togiak River drainage, the Aniak River drainage, and the upper Tikchik lakes of southwest Alaska.

The brown bear population affected by the liberalization had never been studied, and little was known about brown bears in southwest Alaska in general. Objectives of the study were to delineate brown bear home ranges, obtain productivity and survival rates, and collect seasonal habitat use areas and movements. The Kuskokwim Mountain Brown Bear Study began in 1993. Togiak National Wildlife Refuge cooperated with the Yukon Delta National Wildlife Refuge, Alaska Department of Fish and Game, and the U.S. Bureau of Land Management on this study. The WABBMA Working Group, established in 1995 to facilitate local public involvement in research efforts, was also cooperating.

Togiak Refuge and cooperators captured and weighed brown bears within the study area. Males captured averaged 520 pounds, and average weight of females was 290 pounds. Females were fitted with radiocollars (white object on left side of photo). Movements of radiocollared animals were tracked from a fixed-wing airplane every other week while the bears were active (May to October) and once a month while bears were dormant (November to April)

Information collected from radiocollared animals included reproductive parameters (litter size, cub survival), home range, habitat use, bear density (number of bears per 1000 km²), behavior, and mortality (age, cause of death).

Preliminary results indicate that female brown bears in the Kuskokwim Mountains have their first litter of cubs when they are around seven and one-half years old. Cubs are usually twins, and most cubs stay with their mothers for three years. Although most brown bears only live to about 30 years of age in captivity, we observed a mother with cubs who was 29 years old. Average home range size for brown bears in the study is 875 square miles. This home range size is comparable to other Alaskan bears. This study concluded in the spring of 2003, at which time radiocollared bears were recaptured and their collars removed.

Last updated: July 24, 2008