HUMPBACK WHALE

(MEGAPTERA NOVAEANGLIAE)


BIOLOGY

One of the best known aspects of Humpback whales is their acrobatic air shows, when the body of the whale is completely out of the water, entering it back with a huge sideways fall.

The social organization is rather scarce, they are rather lonely individuals. Usually they bind small and unstable groups, sometimes lasting barely a few hours. The most stable groups occur in summer, when they cooperate to find food. They can often be seen with other whales and dolphins, but with very few interspecific interactions between them.

Overall, life expectancy is 40-50 years.


Reproduction:

They reach sexual maturity at 4-6, reaching their adult size shortly after. The males compete intensely with each other for the females and the belief is that their songs are a form of courtship. The procession takes place during winter, and groups of two to twenty males surround a female, performing various displays that serve to establish dominance relationships among males.

Females have calves every two or three years. Gestation lasts 10 to 12 months and pups are nursed for a year, with milk being their only food for the first six months. The next six months, they alternate breast milk and food captured by themselves. Calves accompany their mothers on the return migration to the polar areas, abandoning them early in the second year, when they reach about 9 meters long.


THREATS

· Whaling: humpback whales have always appeared in sailors stories. Whaling has been conducted for several centuries and for different economic reasons: food (fat and protein), heating and lighting (oil), strings (intestines), cosmetics and pharmaceuticals. Whaling increased considerably since the nineteenth century, as the Industrial Revolution improved hunting technologies. It is estimated that during the twentieth century 200,000 whales were hunted, reducing the global population by over 90%. Although whaling is now banned, countries like Japan, Russia, Norway and Iceland continue hunting them. This includes also some populations performing Aboriginal artisanal hunting such as the Eskimos from Alaska, Siberia, Canada and the Caribbean.

· Bycatch: the whales are particularly vulnerable to collisions with ships and to entanglements in fishing gear and drifting nets. Like other whales, humpback whales can be injured by excessive noise.

· Contamination: due to increased pollution in the oceans, whale populations are being affected. They are very vulnerable to changes in the marine environment.

· Climate change: the change in the stocks of fish that are consumed by whales, is causing an imbalance in the entire food chain, directly affecting this species. Eating contaminated fish has already killed several whales. Also they are affected by noise pollution.

· Tourism sightings: humpback whales are very curious, spontaneously approaching boats and swimming around them. This makes them the ideal target species for whale watching all over the world, like the Pacific coast (Washington, Vancouver Island and Alaska), the south coast of the Pacific Ocean (Australia), the north coast of the Atlantic Ocean (New England, Boston), Snaefelsens Peninsula (Iceland), Samana Bay, Banco de Plata (Dominican Republic) and Praia do Forte (Brazil).

The mothers are very protective of her calves and try to always be placed between the boat and the calf. Too much tourism produces a lot of stress on individuals of this species, so tour operators have been asked to follow a code of conduct, to cause minimal stress to the whales during sightings.


original

Photo: Bryant Austin

SCIENTIFIC NAME: Megaptera novaeangliae

Common Name: Humpback whale, bunch, hump whale, hunchbacked whale.

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Cetartiodactyla

Family: Balaenopteridae

Genus:  Megaptera

DESCRIPTION

Their dorsal area is blue-black and their ventral side is white. The pectoral fins are long and can reach a third of the body length (5m approx.) With a black coloration on the back and white on the inside.

The dorsal fin is very small and very variable in shape for each individual, it can be almost absent or high and sickle-shaped.

From the bottom of the mouth to the belly, they have a number of folds that can be expanded when filtering water during feeding, allowing it to considerably increase the volume of the oral cavity. They have between 270 and 400 dark baleen  plates disposed on each side of the mouth, with which they filter the water holding their food.

In the head and jaws they have a series of bumps caused by tubers and barnacles. They have a thick layer of skin and fat,  varying in thickness depending on age, season and physiological condition.

The tail has on its underside a unique pattern in each individual ranging between black and white, and a characteristic serrated edge of the caudal fin.

Often they perform impressive jumps and mysterious songs. When they emerge they expel all the air from their lungs, through both nostrils they have on their back, creating a cloud of up to three meters and often pulling the tail at the beginning of each dive. To perform the immersion generally they tend to arch their back, so that the caudal fins rise above the water clearly visible.

Females have a lobe of 15cm in diameter in the genital region, which differentiates the sexes, since males only have a slot.                                                                                          

CONSERVATION

· Red List (IUCN): classified as Least Concern (LC). The subpopulation of the Arabian Sea and the subpopulation of Oceania are classified as Endangered (EN).

· Bonn Convention (CMS): cited in Appendix I, Convention on Migratory Species.

· Council of the EU: all cetaceans are listed in Annex A of Regulation 338/97, therefore, are treated by the EU as if they were included in Appendix I of CITES, which bans trade.

· United Kingdom: it is a priority species of the Biodiversity Action Plan of the UK. Under the 1981 Wildlife and Countryside Act it is illegal to intentionally kill, injure, capture or harass whales and dolphins in UK waters.

· Costa Rica: they have established a Whale Marine National Park, specially designed for the protection of humpback whales.

· Canada: Species at Risk Act (SARA): off the west coast, they have established the Gwaii Haanas National Park Reserve (3,400Km²), considered a primary feeding habitat for the North Pacific humpback whale. The act considers this population as threatened and of special interest. Thanks to this law, according to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), the humpback whale population is increasing by about four percent annually.

· United States: the Glacier Bay National Park and Preserve and the Cape Hatteras National Seashore, among others, have also become major factors in sustaining populations.        


Size:

Male length: 12-15m             Male weight: 25-30 tons

Female length: 13-16m        Female weight: 25-36 tons

Newborn length: 4-4.5m          Newborn weight: 700 kg


HABITAT

Humpback whales are found in both tropical and polar zones depending on the season and are associated with shallow coastal waters. They can be found in all the oceans between latitudes 60° to 65ºN, although they may reach the edge of the Antarctic ice at 77ºN.

It is estimated that the population is 12,000 individuals in the North Atlantic Ocean, 7,000 in the Pacific Ocean  and 17,000 in the Southern Hemisphere.

They are a migratory species, covering distances of more than 25,000km a year. They spend summers in high latitudes where the waters are cooler and to reproduce they move to tropical or subtropical waters.

Only one population doesn’t migrate, it is the one living in the Arabian Sea (Persian Gulf), where they remain in tropical waters throughout the year.

In the North Atlantic, they live from Scandinavia to New England, Caribbean and Cape Verde.

In the South Atlantic and Indian oceans, the populations are located in Brazil, in the coasts of Central America, South and East Africa, including Madagascar.

A large population inhabits the Hawaiian Islands, from southern to northern Kure Atoll, feeding off the coast of California to the Bering Sea.

Populations have also been observed in the Pacific coast of Costa Rica, Panama, Antarctica, east and west coasts of Australia (Sanctuary Cadmen Sound), New Zealand, Kermadec Islands, fjords of southern Chile, Peru, Asia (China, Japan, Vietnam, Taiwan, Philippines). They have also increased in the eastern Mediterranean Sea, Baltic and Scandinavian fjords such as Kvænangen.


FEEDING

Humpback whales feed intensively in summer and live off their fat reserves during migration and winter, feeding during this stage is rare and opportunistic.

They feed primarily on krill. Also small fish such as herring, Atlantic salmon, capelin, mackerel, coal fish and haddock. In Australian waters and the Atlantic they also feed on copepods.

They have inside their big mouths baleen plates, which are used to filter plankton organisms such as krill from the water.

They capture their prey by stunning them hitting the water with their pectoral or caudal fins or by direct attacks. Another outstanding technique is known as “bubble net”, in which a group of individuals swim in concentric circles under the schools of fish, releasing bubbles in a ring of up to 30m in diameter, which requires the cooperation of several individuals. The circular bubble surrounds the school of fish, concentrating the group in an increasingly smaller cylinder. When fish are sufficiently grouped, whales quickly released on the school taking a big bite and trapping thousands of fish at once. Other groups trap schools of fish by vocalizations.