Megaptera novaeangliae

Humpback Whale

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Humpback Whale

 

Description

Humpback whales are among the best-studied cetaceans, yet they are still among the most mysterious. Among the mysteries are the reasons for their songs and the complex social behaviors that accompany them. These songs are intricate, with up to nine musical themes. Males may sing for days, changing themes over time, yet all the males from one population will sing the same song. Humpbacks are popular subjects for ecotourism and the whale-watching business. They are easily identified by enormous, wing-like flippers, which are far longer than in any other whale. They are known for spectacular displays at the surface. They breach, leaping headfirst out of the water; slap the surface with a long flipper; or slam the tail flukes repeatedly. Humpbacks may be the only whales to trap or herd prey into a bunch to make feeding more efficient. They concentrate a school of fish into a stack by blowing columns of bubbles to form a circle around it, and then lunge into the mass to feed. Although endangered, humpback whale populations are making a good comeback.

Geography

The humpback whale is a cosmopolitan species found in all the major ocean basins (Clapham and Mead 1999), and all but one of the subpopulations (that of the Arabian Sea) migrate between mating and calving grounds in tropical waters, usually near continental coastlines or island groups, and productive colder waters in temperate and high latitudes.

Humpbacks in the North Atlantic range in summer from the Gulf of Maine in the west and Ireland in the east, and up to but not into the pack ice in the north; the northern extent of the humpback's range includes the Barents Sea, Greenland Sea and Davis Strait, but not the Canadian Arctic. They occur mainly in specific feeding areas, as noted below. In the winter the great majority of whales migrate to wintering grounds in the West Indies, and an apparently small number use breeding areas around the Cape Verde Islands.

In the North Pacific their summer range covers shelf waters from southern California, to the Gulf of Alaska, Bering Sea and southern Chukchi Sea, the Aleutian chain and Kamchatka, Kurile Islands, Okhotsk Sea and northeastern Japan. Wintering grounds are off the coasts of Mexico and Central America, around the Hawaiian Islands, the Bonin Islands, Ryukyu Islands and the northern Philippines, and possibly around additional island groups in the western North Pacific.

Humpbacks are abundant throughout the Antarctic in summer south to the ice edge, but not within the pack ice zone. In the winter, Southern Hemisphere whales aggregate into specific nearshore breeding areas in the Atlantic, Indian Ocean and Pacific, two of which extend north of the equator, i.e. off Colombia in the eastern Pacific and in the Bight of Benin in the Atlantic. Some wintering grounds are fairly localized, e.g. around island groups, and some are more diffuse, e.g. along the western coast of southern Africa and the southern coast of West Africa.

There is a resident year-round population in the Arabian Sea, which is genetically distinct from that of the southern Indian Ocean.

Humpbacks rarely enter the Mediterranean and are considered only visitors there (Reeves and Notarbartolo di Sciara 2006).

Ecosystem

Humpback Whales have been recorded across most of the South Pacific, although densities vary from large numbers in East Australia to very low numbers in Fiji (in E3) and parts of French Polynesia. They are regularly found around island groups but also in open water away from islands. Humpbacks have been recorded throughout the southern ocean, including south to the ice edge and in the RossSea.

Little is known regarding life history parameters for the Oceania subpopulation of Humpback Whales, although it is assumed that these rates are similar to those described from whaling records in Australia and New Zealand (Dawbin 1956, 1964, 1966; Chittleborough 1965). One rate that has been preliminarily investigated in the region is calving interval, which is approximately 2-3 years (consistent with that reported from other oceans). The diet of these Humpback Whales consists mainly of krill, which they consume while in Antarctic waters. They are not known to feed while in tropical breeding grounds.

 

Conservation

As of 1999, listed as an endangered species in the ESA. Humpbacks were heavily exploited commercially until 1963 when IWC protection started. Now protected by IWC, CITES, and CRW (mothers and calves, specifically). Population estimated around 25,000 worldwide. 

 

Threats

Although commercial whaling seriously depleted all humpback populations, the species has demonstrated remarkable resilience, and most populations have increased since the end of whaling, although there are several populations that remain small and for which no increase has yet been detected, such as the population in the Arabian Sea, the population breeding near South Pacific islands, and the western North Pacific population. Humpback whales have been protected from commercial whaling worldwide since 1966, and there have been few catches since 1968.

Today, small numbers only are taken by a 'subsistence' whaling operation off St Vincent (1-2 animals per year); it is possible that other small unreported catches occur elsewhere.

The government of Japan announced plans to resume humpback whaling in the Antarctic from the 2007/08 season, starting with an experimental catch of 50 animals per year under scientific permit (Government of Japan 2005). The impact of these catches on small unrecovered stocks of humpbacks in Oceania that feed in the whaling grounds of Area V is not clear.

Also, in humpback habitat off the coasts of Brazil, Gabon, Angola, Mozambique and Madagascar (Breeding Stocks A, B, and C), there is a great deal of ongoing and planned offshore oil and gas development, with potential impacts.

Humpback whales are subject to entanglements, often fatal, in fishing gear. They are also vulnerable to injury by ship strikes, which can also be fatal. The documentation of such incidents is best for US waters. For the Atlantic coasts of the US during 1999-2003, there were 19 reports of death or serious injury caused by entanglements and 7 cases of death or serious injury due to ship strikes (Anon. 2005b). For US Pacific waters (mainly Alaska) during 1999-2001 there were 13 reports of deaths and serious injuries due to entanglement and 3 reports of deaths due to ship strikes (Anon. 2005a).

Japanese Annual Progress Reports submitted to the IWC during 2003-06 listed 3-5 humpback whales caught annually in fishing gear, mainly coastal trap nets (Miyashita and Kato 2006).

In most areas, the observed increases in humpback whale abundance in recent times implies that human-caused mortality is not sufficient to threaten the populations concerned. However, the situation should be kept under review for populations that are still small and for which no increase has been detected, such as the in western North Pacific and parts of Oceania.

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