GROWTH AND SEXUAL DIMORPHISM OF ATLANTIC WALRUSES (ODOBENUS ROSMARUS ROSMARUS) IN FOXE BASIN, NORTHWEST TERRITORIES, CANADA

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Abstract

Growth of Atlantic walruses (Odobenus rosmarus rosmarus) was investigated using morphological data collected in association with Inuit subsistence walrus hunts. Four growth models were examined. The growth parameters of a constrained Richards model were used to quantify growth and to test for sexual dimorphism. The asymptotic length of male walruses (315.2 cm ± 3.8 (SE), n= 103) was significantly larger (t= 7.21, df = 191, P < 0.05) than the asymptotic length of females (276.6 cm ± 3.4, n= 90). Sexual size dimorphism in adults was due to a longer growth period and a faster growth rate in males. The predictive equation relating mass (M, kg) to standard length (SL, cm) was: Log10M= -3.74 + 2.68(Log10SL), n= 25, r2= 0.98. There were no significant differences in the size of male walruses from Foxe Basin collected in the 1950s and this study. There were too few data to compare females. There were no significant differences in size between walruses sampled in Greenland and Foxe Basin in the 1980s and 1990s. Foxe Basin walruses were significantly larger than walruses sampled in northern Hudson Bay in the 1950s. Female Atlantic walruses sampled in Foxe Basin were larger than female Pacific walruses (Odobenus rosmarus divergens) sampled in Alaska.

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