Home range and movements of female brown bears in southwestern Alaska

Abstract

Between 1993 and 2003, 40 adult female brown bears (Ursus arctos) were radiocollared and monitored in the southwest Kuskokwim Mountains of Alaska. The 95% kernel home range size for individuals with ≥50 relocations (n = 20) ranged from 93–623 km2 (x̄ = 356 km2). Bears occupied lower elevations during July and August (x̄ = 454 m) when salmon (Oncorhynchus spp.) were available and higher elevations in September (x̄ = 520 m), presumably to feed on berries, ground squirrels (Spermophilus parryii), and caribou (Rangifer tarandus). During the denning period, bears moved to higher average elevations (x̄ = 632 m), generally remaining through June (x̄ = 570 m). Radiomarked females entered the den in mid October and exited in mid May. There was fidelity to denning areas, with an average distance between consecutive dens of 4.5 km (SD = 3.1). Females with cubs were found at higher average elevations than females without young or with yearlings. Radiomarked females were found closer to anadromous streams from 16 July–15 August, coinciding with chinook (O. tschawytscha), chum (O. keta), and sockeye salmon (O. nerka) availability. Beginning in 1998, chinook and chum salmon escapement was low in the Kuskokwim drainage. There was an inverse relationship between measures of salmon availability and bear distances to anadromous streams. This indicates that although the study area was at the fringe of salmon range, salmon abundance influenced bear seasonal movements and distribution. With reduced salmon availability, this area may support a lower bear density, and brown bear population management should be considered in salmon escapement goals.