Publication Date:
2019-07-17
Description:
The potential effects of ocean warming on marine predators are largely unknown,
though the impact on the distribution of prey in vertical space may have far reaching impacts on
diving predators such as southern elephant seals. We used data from satellite-tracked southern
elephant seals from Marion Island to investigate the relationship between their dive characteristics
(dive depths, dive durations and time-at-depth index values) and environmental variables
(temperature at depth, depth of maximum temperature below 100 m, frontal zone and bathymetry)
as well as other demographic and behavioural variables (migration stage, age-class, track day
and vertical diel strategy). While other variables, such as bathymetry and vertical diel strategy
also influenced dive depth, our results consistently indicated a significant influence of temperature
at depth on dive depths. This relationship was positive for all groups of animals, indicating
that seals dived to deeper depths when foraging in warmer waters. Female seals adjusted their
dive depths proportionally more than males in warmer water. Dive durations were also influenced
by temperature at depth, though to a lesser extent. Results from time-at-depth indices showed that
both male and female seals spent less time at targeted dive depths in warmer water, and were presumably
less successful foragers when diving in warmer water. Continued warming of the Southern
Ocean may result in the distribution of prey for southern elephant seals shifting either poleward
and/or to increasing depths. Marion Island elephant seals are expected to adapt their
ranging and diving behaviour accordingly, though such changes may result in greater physiological
costs associated with foraging.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
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