Formations of foraging sperm whales, Physeter macrocephalus, off the Galápagos Islands

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Abstract
Groups of sperm whales, composed mostly of females and their offspring, which were tracked in the waters off the Galapagos Islands during 1985 and 1987, generally foraged in ranks about 550 m long aligned perpendicular to the direction of travel. While at the surface, they swam in clusters containing a mean of 1.7 whales, and these clusters were spaced out along the rank. When feeding at depth the whales were estimated to be about 40 m apart. The ranks travelled at approximately 2 kn (3.7 km/h) and maintained their headings for periods of several hours. Individuals showed some coordination in the timing of their dives. There were no indications that individual whales, mature males, or first-year calves were more likely to be found in particular positions along the rank. The major benefits for individuals of foraging in a rank are probably gathering information about prey densities, avoiding mutual interference, and possibly catching prey that elude other members of the formation.