Dear colleagues,
The following article was recently published on-line in Marine Mammal Science:
Individual foraging site fidelity in lactating New Zealand fur seals:
Continental shelf vs. oceanic habitats
Baylis, A.M.M, Page, B., McKenzie, J. and Goldsworthy, S.
A copy is available via the journal website, or upon request.
Kindest regards
Al Baylis
[email protected]
www.falklandsconservation.com
Abstract
Wide-ranging marine central place foragers often exhibit foraging site fidelity
to oceanographic features over differing spatial scales (i.e., localized
coastal upwellings and oceanic fronts). Few studies have tested how the degree
of site fidelity to foraging areas varies in relation to the type of ocean
features used. In order to determine how foraging site fidelity varied between
continental shelf and oceanic foraging habitats, 31 lactating New Zealand fur
seals (Arctocephalus forsteri) were satellite tracked over consecutive foraging
trips (14–108 d). Thirty-seven foraging trips were recorded from 11 females
that foraged on the continental shelf, in a region associated with a coastal
upwelling, while 65 foraging trips were recorded from 20 females that foraged
in oceanic waters. There were no significant differences in the mean bearings
(to maximum distance) of consecutive foraging trips, suggesting individual
fidelity to foraging areas. However,
overlap in area and time spent in area varied considerably between continental
shelf and oceanic foragers. Females that foraged on the continental shelf had
significantly greater overlap in consecutive foraging trips when compared to
females that foraged in oceanic waters (overlap in 5 × 5 km grid cells visited
on consecutive trips 55.9% ± 20.4% and 13.4% ± 7.6%, respectively). Females
that foraged on the continental shelf also spent significantly more time within
the same grid cell than females that foraged in oceanic waters (maximum time
spent in 5 × 5 km grid cells: 14% ± 5% and 4% ± 2%, respectively). This
comparatively high foraging site fidelity may reflect the concentration of
productivity associated with a coastal upwelling system, the Bonney Upwelling.
Lower foraging site fidelity recorded by seals that foraged in oceanic waters
implies a lower density/larger scale habitat, where prey are more dispersed or
less predictable at fine scales,
when compared to the continental shelf region.
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