Humpback Whale
The humpback whale (Megaptera noveangliae) has some of the most spectacular aerial displays of all the large baleen whales. The are often seen breaching, raising their mammoth body high out of the water, then falling on their back into the water. Displacing up to 80,000 pounds of water with a single breach, humpbacks may engage in up to 20 successive breaches. The reasons for this behavior are not clear but it could be to displace parasites, signal to other whales, scratch an itch, or just for fun. In any case, propelling 30-40 tons of body weight out of the water requires a lot of energy and produces a lot of excess body heat.
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Humpback Whale Bubble Net Feeding 8/1/05 Juneau, Alaska
Click on the whale for a movie! |
One distinguishing feature of the humpback whale are their long pectoral fins. Notice in the drawing below, the humpback’s pectoral fins can be up to 1/3 the length of the body, or about 15 feet (total length: 50 feet). These long appendages can be used to dispel excess heat. Blood shunted into vessels in the fin will be warmer than the surrounding water, so heat will be lost to the environment. A similar adaptation is seen in the large ears of elephants. Feeding behaviors of humpback whales are unique among the large whales, including one method of rounding up fish known as “bubble net feeding”. This feeding strategy involves one whale emitting a circular stream of bubbles from its blowhole to encompass a school of fish. The bubbles act as a net, effectively concentrating the fish into a tight ball. One whale trumpets a high-pitched “feeding call,” and then the whales charge up through the school with their huge jaws wide open to engulf mouthfuls of fish. When they are hunting cooperatively, one whale may use their large, white pectoral flipper to stun or scare the fish into a corner of the bubble net, thereby further condensing the school into a “bite size” morsel! Humpbacks, like most large baleen whales, feed in polar, nutrient rich waters during the summer season. There is, however, a population of humpbacks that feed in the Gulf of the Farallones, where upwelling brings cold water to the surface, causing a massive planktonic bloom. |
In the late fall, humpbacks will begin their migration to warmer equatorial waters in Hawaii and Mexico to breed. During the winter months male humpback whales engage in a courtship ritual where they produce sounds with a great variety of notes, and have rhythmic patterns that are repeated again and again. These are the songs of the humpback whales. The singing whales remain motionless in the water for the duration of the song, which can go on for up to 24 consecutive hours. Males in an area all sing the same song, and the song changes during the course of the breeding season. The probable reason for the songs is to attract females! The patterns in the songs include high frequency sounds, which reach females closer in proximity and lower frequency sounds, which travel farther under water. More information about the songs of humpback whales, as well as recordings, can be found on websites listed below.
Humpbacks were one of the first species of cetaceans to be individually identified using a method called “photo identification”. The underside of the flukes of humpback whales have a black and white pattern which is unique to each whale. Individuals can be identified by this pattern, so photographs taken of the flukes as the whale dives can be used for identification. This allows scientists to determine social systems of the whales, and track their migratory patterns.
Web Sites:
Hawaii Whale Research Foundation http://www.hwrf.org/
Zoom Whales: Humpback Whales http://www.zoomdinosaurs.com/subjects/whales/species/Humpbackwhale.shtml
Discovery Channel: Humpbacks of Madagascar http://www.discovery.com/exp/humpbacks/humpbacks.htm
