Humpback Whale

Megaptera novaeangliae

HUMPBACK_WHALEClass: Mammalia
Order: Cetacea
SubOrder: Mysticeti
Family: Balaenopteridae
Genus: Megaptera
Species: Novaeangliae

Physical Description
The Humpback whale has distinctive knobbly protuberances on the head and long flippers making this one of the most easily recognised of the large baleen whales. Its name is derived from the hump under the dorsal fin, which is particularly noticeable when the whale arches its back to dive. Each of these bump-like knobs contains at least 1 stiff hair – the purpose of which is not known – though it is thought that they may allow the whale to detect movement in nearby waters. There are at least 20 – 50 ventral grooves which extend slightly beyond the navel.

Length & Weight
Adult males measure up to a maximum length of 15 – 18m and weight of 40 tonne. Adult females measure up to 15m and weigh from 22 to 35 tonne. The flippers are very long, between 1/4 and 1/3 the length of the body, and have large knobs on the leading edge. The flukes (tail) can be up to 5.5m wide and are serrated and pointed at the tips.

Mating and Breeding
Humpbacks do not reach sexual maturity until they are at least seven years old. A single calf is born after a gestation period of approximately 12 months and will generally stay with the female for a further year. The breeding season is characterised by the winter migration to warm tropical waters and the long complex sounds or songs produced by the males during the journey. The reason for these calls is not known but it could be a combination of sexual and territorial display.

Feeding
Humpback Whales main prey, krill and small schooling fish such as mackerel are caught by repeated open mouth lunges into the prey school. The resultant mouthful of water is then expelled through the baleen plates thus trapping the fish, which are then swallowed. This method of feeding can often involve a number of whales in what appears to be a cooperative feeding strategy.

Distribution and Migration
Humpback Whales have a worldwide distribution involving two broad population groups that do not appear to mix – one in the Northern Hemisphere and one in the Southern Hemisphere. It generally inhabits the open ocean except during the annual migration between cold water feeding areas and the warmer calving grounds. During this time they will often appear quite close to the coast and on the journey south (in the Southern Hemisphere) will congregate for short periods in sheltered bays on route. The numbers of Humpback Whales crashed during the peak of the whaling industry especially in the 1960s and 1970s. A total ban on hunting has enabled the populations to slowly recover however they are still considered vulnerable.

Natural History
Humpback whales can launch themselves out of the water in a spectacular motion called breaching. There are theories as to why whales breach. They may be communicating to other whales across vast distances, trying to attract other whales (including a mate), to warn off vessels, or perhaps to cool off, remove parasites such as barnacles, or just for fun! Seen from any distance, this action is one of the most dramatic and awe-inspiring in the animal kingdom.

Humpback whales are one of the most exuberant of all whale species, and are celebrated for their energetic antics and haunting ‘songs’. During migration, male humpback whales often ‘sing’ complex, lengthy and distinctive songs to communicate their presence to females to entice them to mate. They use syllables and rhyming phrases with a complex sequence of clicks, moans and eerie high-pitched wails that can last for a few moments or an hour. The sounds range from canary-like chirps to deep rumbling sounds that carry for hundreds of kilometres. The ‘songs’ change subtly each year and different humpback populations have different songs.

Status
Because the Humpbacks feeding, mating and calving grounds are close to shore and because they are relatively slow swimmers they were an easy target for early whalers. In 1966 the International Whaling Commission (IWC) gave them worldwide protection, but there were large illegal kills by the Soviets until the 1970’s. It is believed that the present population of about 35,000 – 40,000 is approximately 30 – 35% of the original pre-whaling levels.

Acknowledgements
Australian Museum; American Cetacean Society; National Geographic Society; Department of the Environment, Water, Heritage and the Arts