[MARMAM] New paper: Threshold foraging in sympatric rorqual whales within a fjord system

Eric Keen ericmkeen at gmail.com
Tue Mar 14 20:52:55 PDT 2017


Dear colleagues,

I am pleased to announce the release of the following publication in
Ecosphere:

Keen, EM. (2017) Aggregative and feeding thresholds of sympatric rorqual
whales within a fjord system. Ecosphere 8(3): 10.1002/ecs2.1702.

This publication is Open Access; PDFs can be downloaded at:
http://onlinelibrary.wiley.com/doi/10.1002/ecs2.1702/full

Best wishes,

Eric Keen


Abstract:
Rorqual whales (f. Balaenopteridae) supposedly respond to increases in prey
supply according to both aggregative and feeding thresholds. With the
former, they gather in areas above a minimum prey density set by their
basal metabolic needs. With the latter, feeding occurs only above a prey
density set by the energetic cost of lunge feeding. To compare prey
preferences and the two threshold types in sympatric rorquals, I conducted
systematic transect surveys and behavioral observations of humpback whales
(Megaptera novaeangliae) and fin whales (Balaenoptera physalus) in a
British Columbia fjord system. While multiple prey features were found to
influence whale aggregation and feeding, both threshold types were observed
in each species' response to krill volume. Humpback response to prey
features was less predictable and influenced by more factors than that of
fin whales, which appeared to be exclusively euphausivorous and interested
in the deepest high-volume krill patches within the deepest channels.
Compared with fin whales, humpbacks found higher-volume krill patches and
had higher aggregative thresholds, but had lower feeding thresholds.
Findings aligned overall with the expectations that aggregative behavior is
responsive to local prey supply, while feeding thresholds are governed by
less mutable energetic constraints imposed by body size and feeding mode.
Both aggregative and feeding threshold responses appeared to be a function
of local conditions: As total krill-like backscatter increased, feeding
thresholds stabilized (became more nonlinear and more nonrandom), while
aggregative thresholds destabilized. All results emphasized the importance
of incorporating observations of feeding effort in studies of prey
preference and habitat use.
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