Research Technical Report

Unique feeding mechanism defines foraging duration and location in the largest marine predators

Acevedo-Gutiérrez, A., D.A. Croll, and B.R. Tershy (2001)

Manuscript submitted to Nature, 10pp.

ABSTRACT

The blue whale (Balaenoptera musculus) and the fin whale (B. physalus) are the largest predators on earth. Adults average 24.7 and 21.2 m in length, and 92,671 and 52,584 kg in weight, respectively 1 . Although large body size usually extends dive duration in air-breathing vertebrates 2 , these two large species perform short dives for their size 3 (Fig. 1). Two hypotheses may explain this paradox: the foraging behavior of these whales is metabolically expensive or prey are always located in shallow water and disperse quickly during foraging bouts. Optimality models and remote-sensing techniques (time-depth recorders or TDRs) were used for the first time in these species. They demonstrate that lunge feeding at depth reduces foraging dive duration due to exceptionally large energetic costs associated with this unusual feeding behavior. Consequently feeding by these enormous mammals is confined to short durations of submergence and to areas with dense prey aggregations. As a corollary, blue and fin whales may be particularly vulnerable to perturbations in prey abundance.

Cite as: Acevedo-Gutiérrez, A., D.A. Croll, B.R. Tershy. 2001. Unique feeding mechanism defines foraging duration and location in the largest marine predators. Manuscript submitted to Nature, 10pp.