Catalogue of Polar Bear (Ursus maritimus) Maternal Den Locations in the Beaufort and Chukchi Seas and Nearby Areas, 1910–2018

Polar bear den records were derived from on-ground observations by residents and visitors in coastal northern Alaska, chance encounters by petroleum industry personnel, State, Federal and industry ground and aerial surveys for maternal dens in likely polar bear denning habitat, chance encounters during State or Federal polar bear field studies, and through standardized very-high frequency (VHF) aircraft radio-telemetry or satellite radio-telemetry of radio-equipped adult female polar bears. Den records were classified as confirmed following compelling evidence that the structure was used for parturition (e.g., den tenure duration, subsequent observation of the adult with dependent young, post-denning site visitation showing evidence of denning). Dens were classified as probable if there was compelling evidence that denning did occur (e.g., radio-collar sensors indicated prolonged high collar temperature relative to ambient temperatures and low activity relative to that of free-ranging bears) but lacked subsequent field observations of the den itself or the adult with dependent young. Den site position was determined from communication with observers, review of topographic maps, aircraft navigation systems, or hand-held GPS receivers during on-ground site visits, from which coordinates were transcribed onto paper data sheets and then entered manually into an electronic database. Den coordinates derived from satellite radio-telemetry were obtained electronically from the service provider (i.e., through Collecte Localisation Satellites, or CLS, Toulouse, France; http://www.argos-system.org/, or by Iridium satellite communications, Iridium Satellite Communications, McLean, VA, USA) and usually transferred electronically into databases.