Observations of habitat use by polar bears, Ursus maritimus, in the Alaskan Beaufort, Chukchi, and Northern Bering Seas

Abstract

A total of 1 112 Polar Bears (Ursus maritimus) at 482 sightings were recorded during aerial surveys in the Beaufort, Chukchi, and northern Bering Seas conducted primarily during September and October from 1979-1999. Of these bears, 784 were observed offshore at 400 sightings. The surveys were conducted by the Naval Ocean Systems Center and Minerals Management Service; they were designed to monitor the fall Bowhead Whale (Balaena mysticetus) migration. Over the 20-year period, 1 096 620 kilometers of surveys were flown. The majority of the offshore Polar Bears, 595 bears at 290 sightings, and most of the kill sites and polar bear tracks were recorded in 80-100% ice cover. The number of bears per kilometer increased substantially in >24% ice cover, with the highest number observed in 80-100% ice cover. This habitat use probably is related to the availability of seals, their primary prey. There were 328 bears (83 sightings) recorded on land, and most of them were associated with whale carcasses and bowhead whale subsistence harvest sites along the Alaskan Beaufort Sea coast.