Association patterns of cooperative lunge-feeding humpback whales in southeast Alaska

Cynthia D’Vincent
Intersea Foundation

Wednesday, May 10, 2000
3:00 p.m.—Pacific Forum

The Alexander Archipelago in southeastern Alaska hosts the largest aggregation of feeding humpback whales (Megaptera novaeangliae) in the North Pacific. Humpback whales feed in these productive waters during the summer season, utilizing a wide variety of feeding behaviors to capture small schooling fish and euphausiids. One of the most complex strategies is the coordinated feeding maneuver. Cooperative feeding of the humpback whale has been observed over a 19-year period. Using distinctive pigmentation markings on the flipper, we have verified that each whale maintains a constant physical orientation and spatial relationship within groups during the vertical lunge-feeding maneuvers. A uniform vocalization, with a fundamental frequency of approximately 500 Hz, is closely associated with the cooperative feeding behavior, with apparent effect upon the prey, Pacific herring (Clupea harengus). Resightings of humpbacks indicate that cooperative groups align along the continuum from sedentary and territorial to highly nomadic with large home ranges. Group size shows a strong positive correlation with high food resources, while territory size appears responsive to prey density. The average group size is seven animals, with both large and small groups exhibiting similar dive profiles (139 seconds average). This suggests that search and capture time is not regulated by group size.

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Last updated: December 19, 2000