Humpback Whales are Rock and Rollin' on the Seafloor

Picture from FreeDigitalPhotos.net

Picture from FreeDigitalPhotos.net

Humpback whales are one of the most admired ocean mammals due to their tremendous size and grace.  They are known for their surface feeding including acrobatic jumps, which has helped spark the success of the whale watching industry. Humpbacks are known for capturing fish in their large mouths by creating bubble nets with the assistance of other whales in the pod. Humpbacks utilize the lunge feeding method for retrieving prey, primarily herring and sand lance, which entails the whales speeding through large numbers of fish condensed into a “bait ball” with their mouths open. Once inside the humpback’s mouth, baleen plates separate the fish from the water, which is then squirted out of the blowhole, while the fish are passed through the whale’s throat to the stomach. For years scientists believed this was their main technique of acquiring food but the humpbacks that inhabit the Gulf of Maine are proving them wrong. The Stellwagen Bank National Marine Sanctuary and the Great South Channel monitor the local humpbacks using tags and critter cams to track their location and migration patterns. After the data is collected the results are three dimensionally mapped for a visual representation. Recently new data surprised scientists and sparked an entirely new investigation of the humpback whales. The maps showed humpbacks swimming to uncommon depths between 11:00 p.m. and 4:00 a.m. The scientists relied on the critter cams for answers. It showed that the whales were engaging in “bottom side rolls” because the whale’s rostrum, a snot-like projection, hit the seafloor and the whale’s ventral pleats expanded indicating feeding. The scientists theorized that the humpbacks somehow acquired this new skill of shaking up the sand to expose the hidden sand lance, which normally gather around the seafloor at night. The whales perform the bottom side rolls at a rate of 30 rolls per hour at about 1-2 meters above the sea floor. Furthermore, the whales execute the bottom side roll as a group to uncover a larger portion of the sand lance. They speculate that the whales must have a previous family or close bond to have learned this behavior . The same family relationships are viewed during surface feeding when the bubble net is implemented. Humpback whales are a family oriented species that communicate new feeding and survival skills to each other. The scientists investigated other Gulf of Maine humpbacks that focused on herring as a main food source and this behavior was not witnessed.  This discovery will open new doors for understanding the behaviors of the humpback whales and fuel continued research. The only concern with this observed behavior is the risk of the whales becoming entangled in seafloor fishing gear such as, gillnets and trap fisheries. More research needs to be conducted to determine exactly why the humpbacks have resorted to this behavior. A possibility is that the food source at the surface is not as plentiful or the whales are not as successful in capturing prey due to anthropogenic causes. 

National Oceanic & Atmospheric Administration. “Research reveals   bottom feeding techniques of tagged humpback whales in   Stellwagen Bank National Marine Sanctuary.” NOAA: National   Marine Sanctuaries, 26 Sept. 2013. Web. 18 Oct. 2013.

Zieliniski, Sarah. “The bottom feeding behavior of humpback   whales.” Science News: Magazine of the Society for   Science &   The Public, 8 Oct. 2013. Web. 18 Oct. 2013.