provided by EG-BAMM, Meagan Dewar
The humpback whale (Megaptera novaeangliae) is a species of baleen whale and is one of the larger rorqual species, ranging in length from 11 to18 metres and can weigh up to 45 tons. Humpback whales belong to the family of rorqual whales, which are characterised by their flat heads, pointed snouts, round bodies and having their dorsal fins set well back on the body. In humpback whales, the most distinctive feature is their long pectoral fins. Humpback whales not only have the largest pectoral fins of any cetacean species, but also the largest appendage of any living animal with their fins measuring over 15 feet in length or almost one third of the whale’s body. The size of these exceptionally large pectoral fins is also reflected in their Latin name, Megaptera novaeangliae, meaning “long winged from New England.”
Humpback whales perform some of the longest migrations of any mammals, with humpback whales migrating annually from their feeding grounds in the North and South Pole, to their winter breeding grounds in the tropics near the equator. During the breeding season, humpback whales are known for their remarkable surface displays and vocal songs sang by the males during their annual migration.
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The humpback whale is a cosmopolitan species found in all the major ocean basins and all but one of the subpopulations migrate between mating and calving grounds in tropical waters, usually near the continental coastlines and productive colder waters in temperate and high latitudes. In the Southern Ocean humpbacks are abundant throughout the Antarctic during the summer months and can be found south of the ice edge but not within the pack ice. In the winter, humpbacks in the Southern Ocean migrate from their polar feeding grounds to their sub-tropical winter breeding grounds in the Atlantic, Indian Ocean and Pacific. The Southern Hemisphere humpbacks are known feed in areas I-V of the management areas in Antarctic. Currently the International Whaling Commission recognises seven major breeding stocks (A-G). These include; Breeding Stock A - Southwest Atlantic, (Brazil), Breeding Stock B - Southeast Atlantic, (West Africa from the Gulf of Guinea down to South Africa), Breeding Stock C – South western Indian Ocean (coasts of eastern South Africa, Mozambique, Madagascar (southern, western and eastern coasts), Mayotte, the Comoros and other western Indian Ocean island groups), Breeding Stock D – South eastern Indian Ocean (North Western Australia), Breeding Stock E – South west Pacific/North eastern Australia, New Caledonia, Tonga and Fiji, Breeding Stock F - Central South Pacific (Cook Islands and French Polynesia), Breeding Stock G – South east Pacific (Ecuador, Galápagos, Colombia, Panama and Costa Rica). Although not much is known about the summer feeding areas for each breeding stock, the use of photo-identification, genetics data and satellite tracking has provided some information on the potential feeding grounds for each breeding stock. Breeding stock A feeds in the South Georgia/South Sandwich Islands in Area II, Breeding stock D feeds in Antarctic area IV and perhaps eastern area III, breeding stock G feeds along the Antarctic Peninsula and the South Shetlands; whilst breeding stock E feeds in Antarctic areas V. At this stage information on the feeding grounds of breeding stock B, C and F is not available.
Humpback whales can dive to a depth of 150m, with dives lasting anywhere from 3-40 minutes.
Humpback whales grow between 11-18m long, with males being around 1-1.5m shorter than females, and weighing between 24-40 tons. Humpback whales live for around 50 years, becoming sexually mature at around 5 – 10 years of age. At birth calves are around 4-4.6m long and weigh around 1-2 tons. Humpback whales only give birth to one calf, with gestation ranging from 11.5 months, although multiple foetuses have been recorded in dead pregnant whales. Calves remain with their months for approximately 12 months.
Humpback whales are found worldwide in all major oceans. They occur primarily in coastal and continental shelf waters, although they are also known to feed around some seamounts and migrating whales often pass through deep waters.
Like most baleen whales, humpback whales, are strictly carnivorous, feeding on zooplankton and small fish. Their diet includes; euphausiids krill, copepods, herring, sandlance, mackerel, sardines, anchovies and capelin. When feeding humpback whales utilise a filter based system, using their baleen plates to filter their prey from the water column. Baleen whales have developed two different methods of feeding known as lunging and skimming. All rorqual whales, including humpback use the ‘Lunging’ style of feeding, which involves the animal opening its mouth extremely wide, opening the lower jaw almost to a 90 degree angle from the body axis. They depress their tongues and expand their ventral grooves. They then lunge into a school of prey and gulping in great quantities of water. The whales then use their baleen plates to strain the food out of the water. Water is expelled through small gaps in the hairs of the baleen plates.
Humpback whales live for around 50 years, becoming sexually mature at around 5- 10 years of age. Mating and calving occurs during the winter at the winter breeding grounds, with gestation ranging from 10-11 months. At birth calves are around 4-4.6m long and weigh around 1-2 tons, although multiple foetuses have been recorded in dead pregnant whales. Weaning begins at 6 months of age; with calves consuming their first meal upon return to the summer feeding grounds in Antarctica, with nursing continuing until the calf is 12 month old. Calving interval in humpback whales is generally every 2 -3 years.
During the breeding season males sing long complex songs, presumably to attract females and perhaps to establish dominance over other males. During the winter breeding season, males compete aggressively for females, often becoming quite violent, with lunges, tail slashes, charges and blocks. Competitive groups of 2 -20 males can surround a single female in estrous. This behaviour can last for hours, with the composition of the group continuously changing.
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