Abstract:
Access to different environments may lead to
inter-population behavioural changes within a species that
allow populations to exploit their immediate environments.
Elephant seals from Marion Island (MI) and King George
Island (KGI) (Isla 25 de Mayo) forage in different oceanic
environments and evidently employ different foraging
strategies. This study elucidates some of the factors influencing
the diving behaviour of male southern elephant
seals from these populations tracked between 1999 and
2002. Mixed-effects models were used to determine the
influence of bathymetry, population of origin, body length
(as a proxy for size) and individual variation on the diving
behaviour of adult male elephant seals from the two populations.
Males from KGI and MI showed differences in all
dive parameters. MI males dived deeper and longer
(median: 652.0 m and 34.00 min) than KGI males (median:
359.1 m and 25.50 min). KGI males appeared to forage
both benthically and pelagically while MI males in this
study rarely reached depths close to the seafloor and
appeared to forage pelagically. Model outputs indicate that
males from the two populations showed substantial differences
in their dive depths, even when foraging in areas
of similar water depth. Whereas dive depths were not
significantly influenced by the size of the animals, size
played a significant role in dive durations, though this was
also influenced by the population that elephant seals originated
from. This study provides some support for interpopulation
differences in dive behaviour of male southern
elephant seals.
