There has been growing concern over the impact of increased human disturbance and research effects on Antarctic species. The Weddell seal of McMurdo Sound in particular has been used as a model species for over four decades of research, with some individuals handled multiple times over a single season. Using opportunistic data, we performed an assessment of blood indicators in adult males (n = 26) and adult females (n = 24) based on high versus low disturbance areas, with results showing no variation in overall seal health. In addition, we performed a preliminary analysis of blood and faecal indicators of inflammation and stress collected from adult, non-lactating females (n = 13) handled twice in less than two weeks for research purposes. There was no indication of a change in white blood cells, platelets, globulins or haptoglobins, or faecal corticosteroids (all P > 0.05). While based on a small, opportunistic sample size with limited power in some cases, preliminary results indicate there is no acute impact of repeated handling or difference in overall traffic level on adult Weddell seals.

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.

Survival of juvenile Weddell seals Leptonychotes weddellii in McMurdo Sound, Antarctica was examined using 25 years of tagging and resighting data. Using mark–recapture models, we estimated age- and sex-specific apparent survival (survival confounded with emigration) rates of Weddell seals from birth to 6 years of age for 17 cohorts (1973–89). Survival in the first 2 years of life (0.429 and 0.635 for the first and second years, respectively) was lower than annual survival after 2 years of age (0.806), and was significantly lower for males than for females. First-year survival of the 1978 and 1983 cohorts was significantly lower than average first-year survival across cohorts. Reproductive rate of adult females was significantly correlated with first-year survival in concurrent years, but not when first-year survival lagged reproductive rate by 1 year nor with annual survival after 1 year of age. This correlation, however, was only significant in male first-year survival, possibly indicating that survival of males is more dependent on maternal or environmental conditions than survival of females. Average weaning mass varied significantly among cohorts and was nearly correlated to reproductive rate of adult females. This may indicate that maternal condition is reduced in years of low reproduction although more data are needed to test this conclusively.