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Biogeography of Humpback Whales

From:

http://bss.sfsu.edu/holzman/courses/spring%2005%20projects/humpbackwhale.htm

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Mysticeti
Genus: Balaenopteridae
Species: Megaptera novaeangliae

These are excerpts from the webpage that may be of interest to students.

Migration:

During the summer months in both the Northern and Southern Hemisphere, the humpback whales are gorging themselves with food. The high latitudes provide an endless supply of food during the summer, but in the winter, humpbacks migrate to lower latitudes and warmer water. Humpbacks begin their journeys in the Northern Hemisphere as early as October, and it is the mature females and yearling calves (Winn & Winn 1985). It is not proven how humpbacks navigate this migration. Scientists predict that it is a sonar system which acts like a radar for underwater topography (Winn & Winn 1985). Gaskin writes that shallow water near a coast is important, for breeding and calving, as well as warmer water temperature (1982). Findings have recently indicated the possibility that more males than females make the journey to the breeding grounds (BCHSB 1995). Scientists claim that the females possibly stay behind in the hopes of feeding and getting bigger, as size is more important than age in the sexual maturity of a humpback (BCHSB 1995).

Distribution:

Humpbacks have been sighted in every ocean, but tend to stay in concentrated feeding areas (Winn & Winn 1985). Evans (1987) refers to the population as ‘cosmopolitan,’ and claims that there are at least ten separate populations. As noted before, almost all humpback whales have strong migration patterns that take them from the summer feeding grounds in the cold water Arctic and Antarctic, to the breeding grounds of the warm waters of tropical and subtropical regions.

Feeding Grounds:

Humpbacks feed in cold water. The feeding grounds are usually in areas where ocean fronts occur between water masses, areas of upwelling, and dynamic or topographic eddies (Gaskin 1982). The whales will concentrate where there is stability in the vertical water column, because this is where large swarms of phytoplankton and zooplankton concentrate (Gaskin 1982). In the Northeast Atlantic, humpback feeding grounds concentrate the population along the coastlines of the Denmark Strait, the Greenland Sea, and the Barents Sea (Evans 1987). In the North Atlantic, humpbacks can be found heavily in Newfoundland waters, the Gulf of St. Lawrence, and the Gulf of Main (Evans 1987). They also have concentrations in Massachusetts Bay and Cape Cod Bay (Evans 1987). As far as the North Pacific is concerned, humpbacks feed near the Aleutian Islands, the Gulf of Alaska, and the East Bering Sea (Winn & Winn 1985). There are also populations in the Sea of Okhotsk (Evans 1987). In the Southern Hemisphere, humpbacks are dispersed along the coast of Antarctica. The cold water provides a rich supply of euphasiids and krill, so most rorqual species exploit these feeding grounds (Evans 1987). During migration, humpbacks will move mostly along coastlines, but if their destination is in the middle of the ocean, the will swim directly to it (Winn 1985). http://

Breeding Grounds:

Warm shallow waters are ideal for calving. If the calf is born in this environment, it will have a much better chance to build up strength and fat reserves before entering the extremely cold Arctic and Antarctic. Northeast Atlantic populations head south along the western coast of Europe, to the warmer waters of Cape Verde islands of the western coast of Africa. Northwestern Atlantic populations can be found moving southward off the east coast of North America, stopping at the Bermuda Banks, and continuing on to the West Indies, and the Silver, Navidad and Mouchoir Banks north of Hispaniola (Evans 1987). In the North Pacific, whales migrate both in the open ocean, and along coastlines. Part of the population will migrate south down the Pacific Coast, past California and continue on to Baja and Sonora (Evans 1987). Evans also refers to several groups that migrate to coastal islands like the Revillagigedo archipelago (1987). Other parts of the Northeastern Pacific population will herd and move south to the Hawaiian island chain. ‘Hamakua,’ as the Hawaiians call them will breed off the coasts of Maui, Molokai, Lanai and Kahoolawe, as well as the Big Island’s north Kona coast (Evans1987). Some theories were presented claiming that because both the Mexican population and Hawaiian population have similarities in their ‘whale song,’ they may not be considered a separate population, and may have some genetic mixing amongst them (Evans 1987). Humpbacks that feed in the Northwest Pacific will migrate south to the Ryuku Islands, Formosa, and the Bonin Islands (Evans 1987). The migration will take them between Japan and Mainland China. Humpbacks in the South Atlantic can be found migrating off the coasts of both West Africa, as well as the east coast of South America on their way to feed off the coast of Brazil (Evans 1987). In the Southern Indian Ocean, humpbacks will migrate between East Africa and Madagascar, and occupy coastal regions from South Africa to the Horn of Africa (Winn & Winn 1985). Other populations will migrate to the northwestern coast of Australia, and breed there (Winn & Winn 1985). Populations of humpbacks in the south pacific will often be found migrating to the east coast of Australia, as well as Pacific Islands like Tonga and Samoa (Evans 1987). Other populations in the south pacific will migrate along the coast of Chile and western South America to the Galapagos Islands.

Indian Ocean Population:

Although in the Southern Hemisphere humpbacks feed in Antarctica, recently the song of the humpback has been heard in the Indian Ocean when they should, according to migration patterns, not be in the tropics (Evans 1987). Theories about the population origin are widely speculated. Some think that they stay there all year long, others think they migrate from the south, others from the north, and some think they come from both (Winn 1985).