Summer Snow Dens Used by Polar Bears in the Canadian High Arctic

This paper describes the use of snow dens by polar bears during two summers on northern Baffk and Bylot Islands. More dens were found during 1976 than 1975, probably because of heavier snow during 1976. Dens were of three types, shallow surface pits, shallow dens, and deep burrows. This paper describes, for the first time, the use of snow dens by polar bears (Ursus maritimus Phipps) during the summer. Polar bears have long been known to use snow dens during winter throughout their range (Harington, 1%8; L$n& 1970; Jonkel et al., 1972; Uspenski and Kistchinski, 1972; Lentfer, 1976). These dens provide escape from inclement weather for probably all sex and age classes of polar bears and maternity shelter for parturient females (Harington, 1968; Van de Velde, 1971). Polar bears also use earth dens during the summer along the coasts and on the islands of southern Hudson and James Bays as places to avoid heat and insects when they come onto land during the ice free period (Jonke et al., 1972). Some earth dens may be used for winter maternity dens. Jonkel et al., (1972) mentioned the use of snow dens by polar bears in the high Arctic during the summer, but they did not describe these dens in detail. This paper describes some characteristics of the snow dens found during the late summers of 1975 and 1976 and relates numbers of dens found to the climatic conditions during the two seasons. Observations of summer snow dens were made from a helicopter during polar bear capture surveys on northern Brodeur and Borden Peninsulas,