GROWTH IN EARLY-LIFE AND RELATIVE BODY-SIZE AMONG ADULT POLAR BEARS (URSUS-MARITIMUS)

Data on the body lengths (cm) of polar bears (Ursus maritimus), collec ted as part of a long-term ecological study in the Hudson Bay region o f Canada, were examined to test the hypothesis that growth early in li fe influences adult body size. Data for 42 females and 30 males that w ere captured as two-year-olds (2.6-2.9 years), after the period of mat ernal care. and later recaptured as adults were analysed. On average, females increased in length by 11.2% and males by 23.1% between captur es. Relative adult body length was significantly correlated a with rel ative length as a two-year-old in females but not in males. Thus, body length attained by two-year-olds is a weaker determinant of adult bod y length in males than in females. We suggest that, in comparison with females. prolonged growth beyond the period of maternal care may pred ispose the growth and eventual adult body size of male offspring to a greater degree of environmentally mediated variation. Furthermore, whi le data on maternal investment strategies in polar bears are lacking, variation in the allocation of maternal resources to cubs, within and among litters, may have a limited impact on the eventual adult body si ze of any surviving male offspring.