Megaptera novaeangliae
humpback whale

Humpback whales, Megaptera novaeangliae, live in polar and tropical waters, particularly those of the Atlantic, Arctic, and Pacific Oceans. Their range also includes the waters of the Bering Sea and the waters surrounding Antarctica.

The habitat of humpback whales consists of polar to tropical waters, including the waters of the Artic, Atlantic, and Pacific Oceans, as well as the waters surrounding Antartica and the Bering Strait. During migration, they are found in coastal and deep oceanic waters. Generally, they do not come into coastal waters until they reach the lattitudes of Long Island, New York, and Cape Cod, Massachessetts.

Humpbacks are divided into several populations. These are for the most part isolated, but with a little interchange in some cases. There are two stocks in the north Atlantic Ocean and two in the north Pacific. There are also seven isolated stocks in the southern hemisphere.

The cerebellum of humpback whales constitutes about 20% of the total weight of the brain; the brain does not differ much from those of other mysticete whales.

The olfactory organs of humpback whales are greatly reduced and it is doubtful whether they have a sense of smell at all. Their eyes are small and adapted to withstand water pressure. Their external auditory passages are narrow, leading to a minute hole on the head not far behind the eye.

Humpback females are larger than males. They are one of the few species of mammals for which this is true.

The most distictive external features of humpbacks are the flipper size and form, fluke coloration and shape, and dorsal fin shape. Flippers are quite long and can be almost a third of the body length. They are largely white and have knobs on the leading edge. The butterfly-shaped tail flukes bear individually distinctive patterns of gray and white, and have a scalloped trailing edge. The dorsal fin can be a small triangle or sharply falcate, and often has a stepped or humped shape; this is one source of the name "humpback."

There are 14 to 35 ventral pleats or grooves.

Humpbacks have the greatest relative blubber thickness for their size of any rorqual. Megaptera novaeangliae is second only to blue whales in absolute thickness of blubber. Blubber thickness varies at different times of the year, as well as with age and physiological condition.

Baleen plates are usually all black with blackish bristles.

Humpback whales live in groups. They migrate seasonally from the tropics to the northern feeding grounds. In the tropics, they are found in dense aggregations on shallow banks. They are usually deep oceanic migrators between their feeding and breeding grounds; the vast majority of humpbacks do not come into coastal waters until they reach the latitudes of Long Island, New York or Cape Cod, Massachussetts. They tend to disperse more widely in deep waters than when in shallow water.

Humpbacks migrate between northern and southern latitudes in phase with the climactic cycle. Migration is largely connected with the two functions of feeding and reproduction. Megaptera novaeangliae regularly leaves colder waters (where the whales feed during the spring, summer, and fall) to goes to a winter range of shallow tropical banks (where feeding does not occur). These whales also tend to move through coastal waters during migrations when a land mass is in their direct route.

Humpbacks appear in large numbers in subarctic waters during the spring and remain there until the summer. As the season advances, they become less numerous. Humpbacks migrate apparently because they seek warmer water in which to bring forth their young. Pairing and mating also take place at about the same time in the warmer waters.

There is no direct evidence of territoriality. However, there are some types of preferred area sentiments by individuals or groups. This is supported by the seasonal returns to the same feeding and breeding grounds of most humpbacks.

Swimming speed may reach 27 km per hour and during migration, it may reach 3.8 to 14.3 km per hour. Whales with calves swim the slowest, whereas lone whales travel faster than those in groups.

Humpbacks dive 6 to 7 m for 15 to 20 minutes. During diving, blows are not regular and flukes are not lifted as the whale submerges. In longer dives, the flukes are lifted and the animal surfaces between dives for about 4 minutes, while blowing regularly.

Behaviors seen during courtship and feeding are as follows:

1. A whale may slap the water with one of its pectoral flippers.
2. Belly flipping. A whale may lie on its back and alternately slap the water with one flipper at a time.
3. Head up. A whale may raise the dorsal portion of its head horizontally to the surface, then sink back down underwater without tavelling foward.
4. Rolling corollaries of the animal include a raised flipper or flukes lifted vertiically, not horizontally

Megaptera novaeangliae also shows aggressive behaviors. "Escort" whales within a group may accompany whale-calf pairs. They become aggressive towards other humpbacks approaching the groups. They sometimes blow bubbles from their blow holes or mouths as an apparent "screen." It is believed that most "escorts" are males.

Protective or agonistic behavior may involve body thrashing, horizontal tail lashing, and lobtailing. This aggression may also be directed at boats for coming near the groups. In general, groups of whales are more aggressive than individual whales.

These whales also have realtionships with other animals. Humpbacks may compete with other rorquals (especially fin whales) for food. Also, many seabirds prey upon the same food as the humpbacks. Finally, minke whales, have been seen in close proximity to humpback populations.

Like minke whales, and fin whales, humpbacks are generalized feeders. They are highly mobile and opportunistic. Humpbacks feed upon plankton, the plant and animal life at the surface of the ocean's water, or upon fish in large patches or schools. Because of this, humpbacks are classified as "swallowers" and not "skimmers." They do eat commercially exploited fishes. Feeding by humpbacks takes place during the summer.

Atka makerel and Pacific saury are the most commonly found fish prey of humpbacks in the eastern North Pacific Ocean. The former is considered one of the favorite foods of humpback whales in waters off the Western Aleutians and South of the Amchitka Islands. In addition, humpbacks in the North Pacific and the Bering Sea eat euphausiids (krill), mackerel, sand lance, Ammodytes americanus, capelin and herring.

Fishes comprise about 95% of the diet of North Atlantic humpbacks. Those humpbacks living in the Atlantic Ocean, specifically near Cape Cod and Greenland, also eat sand lance, herring and pollock.

Humpbacks near Australia and in the Antartic also feed on euphausiids.

Typically, these whales take both food and water into their mouths. Large volumes can be accomodated because the ventral grooves in the throat allow for expansion. Once the mouth is full, it is closed and the water is pressed out. Meanwhile, the food is caught in the baleen plates and is then swallowed. This process is aided by the internal mechanism of rorqual feeding--the tongue.

Humpbacks have five main feeding behaviors (the first three are more commonly observed than the last two):

1. Ring of foam. Humpbacks have an elaborate feeding behavior in which they lie on the ocean's surface and swim in a circle. While doing so, they strike the water with their flukes forming a "ring of foam," which surrounds their prey. Then, they dive under the ring and resurface in the center with mouth open, allowing them to capture the prey within the ring.
2. Lunging. Humpbacks feed by swimming vertically or obliquely up through aggregations of plankton or fish. This occurs only when their food is abundant. In addition, some variation may occur by means of lateral and/or inverted lunging.
3. Bubble behavior. When these whales use underwater exhalation to create bubble clouds and bubble columns.

Bubble clouds are large inter-connected masses of bubbles formed by one underwater exhalation. Clouds concentrate or herd a mass of prey. Feeding is presumed to occur underwater. After that the humpback rises slowly to the surface within the bubble cloud. After several blows and some shallow diving, the manuever is repeated. Bubble clouds appear to assist in prey detection or capture by immobilizing or confusing prey. Bubble clouds may cause a jumping response among the prey, helping the whale to detect the prey, or it may disguise the whale from the prey.

Bubble columns are formed as a humpback swims underwater in a broad circle while exhaling. An individual column may form rows, semicircles, or complete circles. These circles act like a seive net, concentrating or herding the prey.

4. Tail slashing. In this method of feeding, the individual whale swims in a large circle while slashing its tail through the water. The actual feeding takes place in the center of the turbulence.
5. Inside loop behavior. A whale can make a shallow dive, while hitting the water with its fluke as it submerges. A 180 degree roll is then rapily executed as the animal makes a sharp U turn (the "inside loop") and then lunge feeds slowly through the turbulent area created by its flukes. The whale feeds beside the area of turbulence.
6. Flick-feeding. this occurs only when whales eat euphausiids.

At times, humpbacks combine some of these methods, for example, combining bubble feeding and tail slapping (lobtailing), as they feed on sand lance.

It is important to note that no humpback younger than two years old uses the tail slapping method, although they are weaned from their mothers at one year. However, rudimentary lobtail feeding has been witnessed several times among older post-weaning young.

In addition, no difference has been noted in the frequency of lobtail feeding between the sexes.

Humpback whales staying close to the shore on the Eastern Canadian seaboard damage cod and herring traps and can tear loose long lengths of a set net.

Humpbacks have historically had incredible economic importance to humans. They were one of the nine species hunted intensively by whalers. They were at times the most important constituent of the catch of modern whalers. Their oil was in demand as a kind of burning oil for lamps and as a lubricant for machinery. Whale oil was also used as a raw material for margarine and as a component of cooking fat. Whale meat was processed for human consumption and made into animal feed. Meal made from whale bones was used as fertilizer.

However, these animals are no longer hunted extensively. They do continue to have some economic impact, as ecotourism and whale sighting tours are quite popular in appropriate coastal areas.

Currently, there are an estimated 6,000 humpbacks in the earth's waters, with possibly 1,000 to 3,000 more. The healthiest populations occur in the western north Atlantic Ocean. A few other areas in which there are small populations include the waters near Beguia, Cape Verde, Greenland, and Tonga. Global humpback populations have begun to strengthen, although this species is still a conservation concern.

Humpback whales received some protection in 1985 when the International Whaling Commission instituted a moratorium on commercial whaling. In the early part of the twentieth century, during the modern whaling era, humpback whales were highly vulnerable due to their tendency to aggregate on the tropical breeding grounds and to come close to the shore on the northern feeding grounds.

More than 60,000 humpbacks were killed between 1910 to 1916 in the southern hemisphere, and there were other peaks of exploitation in the 1930's and 1950's. In the North Pacific, there were peak catches of over 3,000 in 1962 to 1963.

In order to combat the problem of depletion, catching humpback whales was prohibited in the Antartic in 1939, although that plan was abandoned in 1949. In the southern hemisphere, hunting was banned in 1963. In the North Atlantic, hunting was banned in 1956. Finally hunting was banned in the North Pacific in 1966.

The common name "humpback" also comes from the animal's tendency to round its back when diving.

Some humpbacks have whitish, oval-shaped scars, which are the marks of parasitic sea lampreys. Humpback whales have few predators other than humans. They are sometimes harassed, perhaps killed, by killer whales, and sharks feed on their dead bodies.

Little is known about the diseases that affect humpback whales. However, true rorquals get cirrhosis of the liver and mastitis. It is unlear as to whether humpbacks also get them.

Humpbacks are the most parasitized of all of the Balaenopteridae. They tend to carry a wide variety of ecto and endoparasites. The number of parasites may be related to the swimming speed of this species. The slow pace of humpbacks is thought to allow accumulation of parasites to occur.

Humpbacks have different types of whale lice living in their scars, scratches, chins, throats, and urogenital slits. Barnacles also live in their throats, chins, and urogenital slits.

Some endoparasites that live within the whales are trematodes, cestodes, nematodes, acanthocephalans. Helminths live in the blubber, liver, mesentery, and intestine, while Ogmogaster ceti (a commensal nematode specific to the Balaenopteridae) lives in the baleen plates.

Pollutants that have been reported from the blubber of humpbacks include DDT, PCBs, chlordane, and dieldrin. The levels of these toxins vary during the migratory pattern of the humpbacks. The levels are highest during feeding and are lowest during breeding.