Reproductive biology and ecology of female polar bears (Ursus maritimus)

摘要: Data on age-specific natality rates, litter size, interbirth interval, age of first reproduction, reproductive senescence, weaning and cub survival were determined for a free-ranging population polar bears inhabiting Hudson Bay, Canada, near the southern limit species range. Serum progesterone levels also females at different stages their cycle to provide corroborative support parameters described. Animals live captured using immobilizing drugs each animal uniquely marked future identification. First parturition occurred four or five years rate increased with until approximately 20 years, after which it dropped markedly. At least 40% adult displayed two-year intervals 55% cubs in second year independent mother. Mean size litters spring was 1.9 13% had three more cubs. The 5–20-year-old estimated as 0.9, higher than that reported any northerly bear populations where are rare, fewer 5% yearling weaned triplet occur less 1% frequency. Cub mortality initially high declined age. Although western Bay younger lighter weight counterparts northern populations, rates similar. reason differences is not known. We speculate sea-ice conditions may be sufficiently allow body hunt seals successfully there further north.