Growth in early life and relative body size among adult polar bears ( Ursus maritimus )

• Published in: Journal of Zoology
• Main Authors: Atkinson, S. N., Stirling, I., Ramsay, M. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Canada; Hudson; Hudson Bay; polar bear; Ursus maritimus
• Online Access: http://dx.doi.org/10.1111/j.1469-7998.1996.tb05449.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1469-7998.1996.tb05449.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1996.tb05449.x; https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1996.tb05449.x

Data on the body length (cm) of polar bear ( Ursus maritimus ), collected as part of a long‐term ecological study in the Hudson Bay region of Canada, were examined to test the hypothesis that growth early in life influences adult body size. Data for 42 females and 30 males that were captured as two‐year‐olds (2.6‐2.9 years), after the period of maternal care, and later recaptured as adults were analysed. On average, females increased in length by 11.2% and males by 23.1 % between captures. Relative adult body length was significantly correlated with relative 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 body length in males than in females. We suggest that, in comparison with females, prolonged growth beyond the period of maternal care may predispose the growth and eventual adult body size of male offspring to a greater degree of environmentally mediated variation. Furthermore, while 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 size of any surviving male offspring.