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Age‐specific reproductive performance of female polar bears ( Ursus maritimus )
Author(s) -
Derocherand A. E.,
Stirling I.
Publication year - 1994
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1994.tb04863.x
Subject(s) - ursus maritimus , biology , litter , reproduction , predation , bay , reproductive success , ecology , zoology , demography , population , arctic , sociology , civil engineering , engineering
Age‐specific patterns of maternal weight, litter size, litter weight and reproductive effort were investigated for polar bears ( Ursus maritimus ) from western Hudson Bay. Most relationships were described by quadratic equations. Maternal weight in spring and autumn increased until 17 and 15 years of age, respectively, and then declined. Age‐related increases in maternal weight were thought to be associated with improving hunting skills. The relationships between age and litter size, litter weight and reproductive effort, in both the spring and autumn, increased until 14 to 16 years, followed by a decline. We speculate that age‐related decreases in reproductive performance are due to undetennined processes associated with ageing that impair the accumulation of fat stores necessary for reproduction. Pregnant females lost an average of 127 kg overwinter which represented an average of 43.5% of their autumn weight. Fat stores remaining after the overwinter fast may be critical for maintaining an energy supply to cubs once they return to the sea ice where the distribution and abundance of their prey is unpredictable. We suggest that maternal condition is an important factor contributing to lifetime reproductive success in polar bears.