Site fidelity of Weddell seals: the effects of sex and age

Abstract

Site fidelity is believed to be an important life history strategy for Weddell seals (Leptonychotes weddellii), that return to traditional breeding colonies each spring. We examined four hypotheses concerning their fidelity to these colonies: 1) fidelity is stronger to natal sites (natal fidelity) than to other sites, 2) females exhibit greater site fidelity than males, 3) site fidelity for both sexes increases with age, 4) site fidelity in adult females is related to their reproductive status and their total number of offspring. Analysis of a long-term tagging database from McMurdo Sound did not support hypotheses 1 and 2. Although animals did express fidelity to specific sites over their lifetime (χ² tests, P < 0.05), fidelity to natal colonies was lower than to other sites (χ² test, P < 0.05). There were no differences in site fidelity between males and females (χ² tests, P > 0.05). Hypothesis 3 was supported. Since the probability of a returning seal occupying the same colony as the previous year increased with age among both sexes to about age 12. Finally, in support of hypothesis 4, females with a higher degree of site fidelity were more likely to both have a higher reproductive rate and return to a site where they have previously given birth.