Saturday, April 2, 2011
April 2, 2011 : Humpback Whale
The humpback whale (Megaptera novaeangliae) is a species of baleen whale. One of the larger rorqual species, adults range in length from 12–16 metres (39–52 ft) and weigh approximately 36,000 kilograms (79,000 lb). The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the water. Males produce a complex whale song, which lasts for 10 to 20 minutes and is repeated for hours at a time. The purpose of the song is not yet clear, although it appears to have a role in mating.
Found in oceans and seas around the world, humpback whales typically migrate up to 25,000 kilometres (16,000 mi) each year. Humpbacks feed only in summer, in polar waters, and migrate to tropical or sub-tropical waters to breed and give birth in the winter. During the winter, humpbacks fast and live off their fat reserves. The species' diet consists mostly of krill and small fish. Humpbacks have a diverse repertoire of feeding methods, including the bubble net feeding technique.
Like other large whales, the humpback was and is a target for the whaling industry. Due to over-hunting, its population fell by an estimated 90% before a whaling moratorium was introduced in 1966. Stocks have since partially recovered; however, entanglement in fishing gear, collisions with ships, and noise pollution also remain concerns. There are at least 80,000 humpback whales worldwide. Once hunted to the brink of extinction, humpbacks are now sought by whale-watchers, particularly off parts of Australia, New Zealand, South America, Canada, and the United States.
Humpback whales are rorquals (family Balaenopteridae), a family that includes the blue whale, the fin whale, the Bryde's whale, the sei whale and the minke whale. The rorquals are believed to have diverged from the other families of the suborder Mysticeti as long ago as the middle Miocene. However, it is not known when the members of these families diverged from each other.
Though clearly related to the giant whales of the genus Balaenoptera, the humpback has been the sole member of its genus since Gray's work in 1846. More recently though, DNA sequencing analysis has indicated the Humpback is more closely related to the gray whale (Eschrichtius robustus) and to certain rorquals, such as the fin whale (Balaenoptera physalus) than it is to other rorquals such as the minke whales. If further research confirms these relationships, it will be necessary to reclassify the rorquals.