Migration and foraging strategies at varying spatial scales in western North Atlantic right whales: a review of hypotheses

Abstract

Western North Atlantic right whales (Eubalaena glacialis) utilise several important foraging habitats off the northeastern United States andeastern Canada, where they feed on dense patches of zooplankton. At a fundamental level, a right whale’s optimal strategy should be tolocate and exploit the prey patches with the highest net energetic return from foraging. There remain many questions, however, concerningtheir migration and foraging strategies and the environmental cues and sensory modalities involved in migration and foraging, all of whichare likely to vary at different spatial scales. For example, a right whale most likely uses different mechanisms and strategies for locationof primary feeding grounds than those used for detection of optimum prey patches within a feeding area. This paper proposes a multi-scaled,hierarchical, conceptual model of right whale migratory and foraging strategies and presents a variety of hypotheses concerning themechanisms involved. Right whales may return to the general area of their feeding grounds based on prior experience. The locations ofsuccessful foraging in the immediately preceding years are likely to be re-visited, as are habitats to which an animal was exposed whileaccompanying its mother during its first year of life. It is also possible that the whales utilise large- or medium-scale environmental cues,such as currents, temperature discontinuities, or salinity signals indicating coastal plumes, to locate likely areas of high zooplankton patchdensity. Whilst on their feeding grounds, right whales tend to be aggregated, but there are usually outliers which may represent occasionalexcursions in search of other prey patches, though there is currently no evidence to address whether they communicate information aboutprey to other individuals. Their behaviour whilst actively feeding indicates that they can detect differences in patch density and adjust theirbehaviour accordingly. A likely sensory mechanism for quantification of patch density and triggering of feeding behaviour would be thevibrissae around the anterior opening of the mouth.