Abstract:
Strategies employed by wide-ranging foraging animals involve consideration of habitat
quality and predictability and should maximise net energy gain. Fidelity to foraging sites is
common in areas of high resource availability or where predictable changes in resource
availability occur. However, if resource availability is heterogeneous or unpredictable, as it
often is in marine environments, then habitat familiarity may also present ecological benefits
to individuals. We examined the winter foraging distribution of female Antarctic fur seals,
Arctocephalus gazelle, over four years to assess the degree of foraging site fidelity at two
scales; within and between years. On average, between-year fidelity was strong, with most
individuals utilising more than half of their annual foraging home range over multiple years.
However, fidelity was a bimodal strategy among individuals, with five out of eight animals recording
between-year overlap values of greater than 50%, while three animals recorded values
of less than 5%. High long-term variance in sea surface temperature, a potential proxy
for elevated long-term productivity and prey availability, typified areas of overlap. Withinyear
foraging site fidelity was weak, indicating that successive trips over the winter target
different geographic areas. We suggest that over a season, changes in prey availability are
predictable enough for individuals to shift foraging area in response, with limited associated
energetic costs. Conversely, over multiple years, the availability of prey resources is less
spatially and temporally predictable, increasing the potential costs of shifting foraging area
and favouring long-term site fidelity. In a dynamic and patchy environment, multi-year foraging
site fidelity may confer a long-term energetic advantage to the individual. Such behaviours
that operate at the individual level have evolutionary and ecological implications and
are potential drivers of niche specialization and modifiers of intra-specific competition.
