Humpback Whales Are Primarily Bottom Feeders [VIDEO]
Building off recent research that documented three distinct types of bottom feeding tactics deployed by humpback whales, further study has concluded that bottom feeding is the primary means of attaining sustenance for the humpback whales in the Gulf of Maine.
Humpback whales in the southern Gulf of Maine spend more time bottom feeding than they do using air bubbles to corral and "trap" their prey, which has long been considered a primary method of feeding for the whales, according to a release from the University of New Hampshire.
The find also brings to light some conservation issues, including fishing equipment placed on the gulf floor that may pose a danger to the whales.
"Humpbacks have not been known as bottom-feeders, yet this is their dominant feeding mode in this region," said University of New Hampshire professor of data visualization Colin Ware, lead author of a paper published in the journal Marine Mammal Science in July. "You've got this prominent species, and until now nobody knew how they were doing most of their feeding."
The researchers collected their data by affixing devices that record motion and sound to the whales with strong suction cups. Then, with a custom piece of software written by Ware, the data collected by the whales was used to create 3-D illustrations of the movement of the whales at the time the data was collected. In all, data was gathered from 52 individual whales.
The data highlighted the frequency with which each whale performed specific movements, such as diving to the bottom of the ocean, rolling on its side, tilting its head and feasting on side lance, a favorite food.
Ware and his colleagues, which included David Wiley of the Stellwagen Bank National Marine Sanctuary of the National Oceanic and Atmospheric Administration (NOAA) and Ari Friedlaender of Duke University Marine Laboratory and Pratt School of Engineering, documented the whales between 2004 and 2009.
They identified three distinct types of behavior exhibited by whales when bottom feeding: 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," Wiley recently said. "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."
Additional humpback data was collected via a National Geographic Society "Crittercam", which provides a whale's-eye view into what the creatures see when they are beneath the waves.
But Ware is quick to point out that there is still much more to learn about the bottom-feeding behavior of the humpback whale.
"The big mystery is we still don't know exactly how they're feeding. We don't know the mechanism," he said.