APPARENT BOTTOM FEEDING BY HUMPBACK-WHALES ON STELLWAGEN BANK

Humpback whales, Megaptera novaeangliae, on Stellwagen Bank of eastern Massachusetts, U.S.A., apparently bottom feed on northern sand lance, Ammodytes dubius. The feeding behavior is characterized by the whales brushing the bottom in depths of less than 40 m, causing sand lance b urrowed in the bottom to be flushed up into the water column. The grea test densities of sand lance were in beds of shells and shell debris, termed ''shell hash.'' The brushing against or along the bottom, parti cularly in these shell hash areas, caused the humpbacks to acquire abr asions and wounding, sometimes rather extensive, of the lateral lower jaw, and lateral and dorso-lateral upper jaw, here termed ''jaw scuffi ng.'' Scuffing of the dorsal fin and fluke edges was also common and m ay be at least partially related to this feeding behavior. Both mature and immature, and male and female, humpbacks exhibited jaw scuffing. The bottom-feeding behavior was not exclusive, as jaw-scuffed individu als were also observed to use other feeding behaviors. In recent years (1991-1933), however, bottom feeding appears to have became relativel y more common, particularly among young animals. Overall, in the Stell wagen Bank area between 1979 and 1993, a majority of the population en gaged in, or had engaged in, bottom feeding and the associated prey fl ushing.