NATAL SITE FIDELITY IN NORTHERN FUR SEALS, CALLORHINUS-URSINUS

More than 37 000 records of northern fur seals tagged at their natal areas and resighted during a recent mark-recapture study and past commercial harvests, were analysed to study the age and sex variation, and temporal dynamics of natal site fidelity in this highly polygynous, long-lived, migratory species. Data were available on males (2-6 years old) and females (2-20 years old). All ages and sex classes with sufficient sample sizes to allow statistical tests showed a significant tendency to return to the same area of the island where they were born. The proportion of young male and female seals found at their natal area during the breeding season increased significantly with age. Young females showed significantly greater age-specific natal site fidelity than young males (ages 2-6 years) and apparently exhibited their maximum site fidelity at a younger age than males. The increasing expression of natal site fidelity with age appears to be related to sexual maturation and reproductive activity, the latter beginning later in males than in females. Within a season, natal site fidelity of juvenile males increased with time since arrival on St Paul Island. This change in site fidelity implies that they may be less particular in selecting a landing site when they first arrive, then begin to orient more specifically towards their natal area. This behaviour may indicate a transition from a general homing goal while migrating (the island as a whole) to a more specific goal (the natal area) upon arrival. (C) 1995 The Association for the Study of Animal Behaviour