| Travelling Australia http://www.travelling-australia.info |
PHOTOGRAPHS BIRDS JOURNALS |
 | |
| HOME | BACK |
| Humpback Whale - Megaptera novaengliae | |
|
| Humpback whale off Twofold Bay. |
 The humpback whale can be distinguished from other whales by extremely long flippers, reaching nearly a third of the body length. Distinctive knobby protruberances on the head are an additional identification feature for the species. These whales are black on top, and mottled black and white on the underside. Flipper colour ranges from all black to all white. Tail flukes are curved with serrated trailing edge; the underside of the tail fluke is black and white and carries a pattern unique to each whale; the colour pattern and shape of the tail flukes, combined with the shape of the dorsal fin, allows researchers to identify each individual whale at sea. A small dorsal fin distinguishes the humpback from the Southern Right Whale. Humpback whales generally inhabit the open ocean except during the annual migration between cold water feeding areas in the Antarctic (south of 55° S latitude) and warmer calving/mating ground off Queensland and north Western Australia. During this time they often appear quite close to the coast and, on the journey south, congregate for short periods in sheltered bays. During the return to the Antarctic, humpbacks are the focus of whale watching especially on the east coast. From late September to November a stream of whales can be seen leisurely, but purposefully, moving southward close inshore along the coast of New South Wales and southern Queensland. There is a definite order during migration. Immature animals and females with yearling calves lead the way on the northern migration; these are followed by adult males, then non-pregnant mature females with pregnant females at the rear. The order on the southward migration is similar with cow/calf pairs travelling last. Populations on the east and west coast are distinct. A few humpbacks observed in the eastern Great Australian Bight (at the Head of the Bight and near Kangaroo island) are thought to be strays from the east coast population. East coast humpbacks (known as Group V population) have their Antarctic feeding grounds between longitude 150° and 180° (south of the Tasman Sea between Australia and New Zealand) and use the Coral Sea area as their calving and mating ground. West coast humpbacks (known as Group IV population) have the Antarctic feeding ground between longitude 80° and 110° and use areas off north-west Western Australia for calving and mating. Humpback whales are baleen whales feeding on krill (small shrimp-like custaceans) and small schooling fish such as mackeral; each whale eats up to 1300 kilograms per day. Baleen whales do not have teeth; they have 270-400 fringed overlapping plates of baleen hanging from each side of the upper jaw. During feeding, the whale lunges with mouth open into schools of prey taking large volumes of water and food into the mouth; pleated grooves in the throat expand and increase the volume of water taken in. As the mouth closes, water is expelled through the baleen plates trapping food on the inside near the tongue and ready to be swallowed. Male humpback whales regularly produce 'songs' on the breeding grounds. A song includes many sounds such as moans, cries, clicks, squeeks, roars and whistles lasting from 5 to 30 minutes and sometimes repeated identically for hours. Songs differ between populations (i.e. there are substantial differences between song of the east and west coast populations) and change slightly from year to year within each population. A range of surface activity may be observed including flipper and tail slaps, breaching and spyhopping (hanging vertically at the surface with the head and eyes in air so the whale can see around). |
| Humpback Whales - page 2 | ||
| ||
| ||
| ||
|
Adults grow to at least 15 metres long, females are larger than males; average adults weigh 40,000 kilograms. They are thought to live for about fifty years.
Humpbacks can stay submerged for up to 30 minutes but most dives last no longer than 15 minutes with 3 to 10 minutes more usual. When resting near the surface whales may blow every few seconds. The blow is a single, tall and bushy cloud 2 to 4 metres high. The whale arches its back when diving; leaving the tail as the last part of its body visible as the animal submerges. Humpback whales usually remain near the surface in the upper 100 metres of ocean. Speed when leisurely moving is 3.5 knots to 5 knots. Females with calves swim at about 3 knots; average migration speed is 1.3 to 3.6 knots. Swimming speed when chased can reach 9 or 10 knots. Sexual maturity is reached at 6 to 8 years of age. Gestation period is 11 to 12 months. Calves born in tropical waters are 3 to 4.5 metres long at birth, weighing up to 1300 kilograms. The mother suckles the calf for about twelve months before weaning it to solid food. The normal reproductive rate is recorded as one calf every two to three years but it appears that humpbacks are breeding once per year while numbers are so low. The Humpback was an easy target for early whalers because of its slow swimming speed and habit of feeding, mating and calving inshore and numbers declined sharply while they were hunted. The International Whaling Commission (IWC) gave them protected status in 1966. The population did not begin to recover until the 1970s, possibly due to continued illegal whaling; it is now assessed that population has returned to about a quarter of the original population. |
 |
| Humpback whale feeding. The left side of the mouth is above the surface and the front of the whale is to the right. The knobby part is the top of the upper jaw with baleen visible protruding from the underside. Seawater will be forced out of the mouth through the baleen which will retain food items to be swallowed. Humpbacks do not routinely feed during migration south; they are known to feed in only a few places including off Twofold Bay. |
|
|
Information. ¶ The Whale's Journey - A year in the life of a humpback whale, and a century in the history of whaling. by Stephen Martin, pub Allen & Unwin, Sydney, 2001. ¶ "The action plan for Australian Cetaceans - Humpback Whale" prepared by the Department of the Environment, at www.environment.gov.au/coasts/publications/cetaceans-action-plan/whaleap5a18.html |
|
| 5 March 2007 |
|
| http://www.travelling-australia.info/Infsheets/Humpback.html |
| TOP |
|