NATAL SITE FIDELITY IN NORTHERN FUR SEALS, CALLORHINUS-URSINUS

More than 37 000 records of northern fur seals tagged at their natal a reas and resighted during a recent mark-recapture study and past comme rcial harvests, were analysed to study the age and sex variation, and temporal dynamics of natal site fidelity in this highly polygynous, lo ng-lived, migratory species. Data were available on males (2-6 years o ld) and females (2-20 years old). All ages and sex classes with suffic ient sample sizes to allow statistical tests showed a significant tend ency to return to the same area of the island where they were born. Th e proportion of young male and female seals found at their natal area during the breeding season increased significantly with age. Young fem ales showed significantly greater age-specific natal site fidelity tha n young males (ages 2-6 years) and apparently exhibited their maximum site fidelity at a younger age than males. The increasing expression o f natal site fidelity with age appears to be related to sexual maturat ion and reproductive activity, the latter beginning later in males tha n in females. Within a season, natal site fidelity of juvenile males i ncreased with time since arrival on St Paul Island. This change in sit e fidelity implies that they may be less particular in selecting a lan ding site when they first arrive, then begin to orient more specifical ly 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 Assoc iation for the Study of Animal Behaviour