Pregnancy rates and serum progesterone levels of polar bears in western Hudson Bay

摘要: Blood samples were collected from 354 female polar bears (Ursus maritimus) on 476 occasions between 1982 and 1990. Serum progesterone concentrations determined to evaluate reproductive status. Progesterone levels greater than 2.5 ng/mL considered indicative of pregnancy in autumn. Of 85 females classified as pregnant that seen the following year, 67% with cubs 33% without cubs. Possible explanations for large proportion apparent failure include neonatal mortality, implant, or abortion. The minimum weight a confirmed autumn was 189 kg, but approximately 10% suspected below this may have had insufficient fat stores fast through winter produce Based levels, implantation appeared occur mid-September mid-October, likely followed by parturition mid-November mid-December. annual rate solitary females, determined...