Humpback whales feed on bottom, too

New NOAA-led research on tagged humpback whales in Stellwagen Bank National Marine Sanctuary off Massachusetts has revealed a variety of previously unknown feeding techniques along the seafloor.

Rather than a single bottom feeding behavior, the whales show three distinct feeding approaches: simple side-rolls, side-roll inversions, and repetitive scooping.

A recently published paper in the journal Marine Mammal Science indicates that bottom side-roll techniques are common in the sanctuary and the Great South Channel study area, a deep-water passage between Nantucket and Georges Bank to the southeast.

The study further states that this feeding behavior also leads to vulnerability to entanglement in bottom set fishing gear, an issue which is a major mortality factor for the species. This finding reaffirms a NOAA Fisheries regulation that mandates the use of sinking line between fishing traps used in the lobster fishery as a way of reducing entanglements.

The new findings follow earlier studies detailing “bubble net” feeding behaviors near and at the surface.

“Tagging technology is allowing us to observe whales underwater, much as land-based biologists study animal subjects in their specific environments,” said David Wiley, sanctuary research coordinator and co-author on the paper. “The data have allowed us to detect new feeding techniques as well as nuances in those behaviors. We have determined that bottom feeding is a much more commonly used technique than the more well known bubble net behaviors.”