Humpback Whale's Bottom Feeding Tactics Revealed [VIDEO]

Humpback whales employ a variety of bottom feeding techniques on the ocean floor, researchers have learned after studying whales tagged in the Stellwagen Bank National Marine Sanctuary off the coast of Massachusetts.

Rather than a single bottom-feeding behavior, the whales use three distinct strategies when dining upon the sea floor, according to NOAA-led research published in the journal Marine Mammal Science.

Researchers have labeled the humpback's bottom feeding styles as simple side-rolls, side-roll inversions, and repetitive scooping.

"Tagging technology is allowing us to observe whales underwater, much as land-based biologists study animal subjects in their specific environments," said David Wiley, research coordinator at Stellwagen Bank National Marine Sanctuary and a 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."

Bubble net behavior refers to a surface-feeding tactic in which the whales corral schools of fish into a small, edible area by trapping them in nets of air bubbles. Bubble netting is used by individual whales as well as by pairs in coordinated feeding efforts.

On the sea floor, the humpback whales prey upon the sand lance, which tend to burrow into the sediment at night or form schools close to the sea floor. Researchers learned that the whales will do what it takes to get the bottom-dwelling fish. The whales were observed rolling from normal position to anywhere from 45 to 135 degrees to the side in order to catch the prey, a technique the researchers have dubbed the side-roll. A side-roll inversion happens when the whale rotates beyond 135 degrees from normal "upright" position. One humpback was observed using a technique that employed a repetitive sequence of "scooping" moves every 20 or so feet as the whale rolled from a 90 degree position to completely inverted.

The researchers hypothesize that humpback side-rolls may be similar to the feeding technique of gray whales in the Pacific. The variety of bottom-feeding techniques observed may be due to different prey distributions or could just reflect individual preference between whales.

Occasionally, a humpback whale will be spotted with scarring on its head near the mouth. The researchers suspect that the scarring is a result of scraping their heads on the sea floor during bottom feeding situations.