| Humpback whale[1] | |
|---|---|
| Size compared to an average human | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Subclass: | Eutheria |
| Order: | Cetacea |
| Suborder: | Mysticeti |
| Family: | Balaenopteridae |
| Genus: | Megaptera Gray, 1846 |
| Species: | M. novaeangliae |
| Binomial name | |
| Megaptera novaeangliae Borowski, 1781 |
|
| Humpback whale range | |
The humpback whale (Megaptera novaeangliae) is a species of baleen whale. One of the larger rorqual species, adults range in length from 12–16 metres (39–52 ft) and weigh approximately 36,000 kilograms (79,000 lb). The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the water. Males produce a complex song, which lasts for 10 to 20 minutes and is repeated for hours at a time. The purpose of the song is not yet clear, although it appears to have a role in mating.
Found in oceans and seas around the world, humpback whales typically migrate up to 25,000 kilometres (16,000 mi) each year. Humpbacks feed only in summer, in polar waters, and migrate to tropical or sub-tropical waters to breed and give birth in the winter. During the winter, humpbacks fast and live off their fat reserves. The species' diet consists mostly of krill and small fish. Humpbacks have a diverse repertoire of feeding methods, including the bubble net feeding technique.
Like other large whales, the humpback was and is a target for the whaling industry. Due to over-hunting, its population fell by an estimated 90% before a whaling moratorium was introduced in 1966. Stocks have since partially recovered; however, entanglement in fishing gear, collisions with ships, and noise pollution also remain concerns. There are at least 80,000 humpback whales worldwide. Once hunted to the brink of extinction, humpbacks are now sought by whale-watchers, particularly off parts of Australia, New Zealand, South America, Canada, and the United States.
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A phylogenetic tree of animals related to the humpback whale |
Humpback whales are rorquals (family Balaenopteridae), a family that includes the blue whale, the fin whale, the Bryde's whale, the sei whale and the minke whale. The rorquals are believed to have diverged from the other families of the suborder Mysticeti as long ago as the middle Miocene.[3] However, it is not known when the members of these families diverged from each other.
Though clearly related to the giant whales of the genus Balaenoptera, the humpback has been the sole member of its genus since Gray's work in 1846. More recently though, DNA sequencing analysis has indicated the Humpback is more closely related to certain rorquals, particularly the fin whale (Balaenoptera physalus), and possibly to the gray whale (Eschrichtius robustus), than it is to rorquals such as the minke whales.[4][5] If further research confirms these relationships, it will be necessary to reclassify the rorquals.
The humpback whale was first identified as "baleine de la Nouvelle Angleterre" by Mathurin Jacques Brisson in his Regnum Animale of 1756. In 1781, Georg Heinrich Borowski described the species, converting Brisson's name to its Latin equivalent, Balaena novaeangliae. Early in the 19th century Lacépède shifted the humpback from the Balaenidae family, renaming it Balaenoptera jubartes. In 1846, John Edward Gray created the genus Megaptera, classifying the humpback as Megaptera longpinna, but in 1932, Remington Kellogg reverted the species names to use Borowski's novaeangliae.[6] The common name is derived from the curving of their back when diving. The generic name Megaptera from the Greek mega-/μεγα- "giant" and ptera/πτερα "wing",[7] refers to their large front flippers. The specific name means "New Englander" and was probably given by Brisson due the regular sightings of humpbacks off the coast of New England.[6]
Humpback whales can easily be identified by their stocky bodies with obvious humps and black dorsal coloring. The head and lower jaw are covered with knobs called tubercles, which are actually hair follicles and are characteristic of the species. The fluked tail, which it lifts above the surface in some dive sequences, has wavy trailing edges.[8] There are four global populations, all under study. North Pacific, Atlantic, and Southern Ocean humpbacks have distinct populations which complete a migratory round-trip each year. The Indian Ocean population does not migrate, prevented by that ocean's northern coastline.
The long black and white tail fin, which can be up to a third of body length, and the pectoral fins have unique patterns, which make individual whales identifiable.[9][10] Several hypotheses attempt to explain the humpback's pectoral fins, which are proportionally the longest fins of any cetacean. The two most enduring mention the higher maneuverability afforded by long fins, and the usefulness of the increased surface area for temperature control when migrating between warm and cold climates. Humpbacks also have 'rete mirable', a heat exchanging system, which works similarly in humpbacks, sharks and other fish.
Humpbacks have 270 to 400 darkly coloured baleen plates on each side of the mouth. The plates measure from a mere 18 inches (46 cm) in the front to approximately 3 feet (0.91 m) long in the back, behind the hinge. Ventral grooves run from the lower jaw to the umbilicus about halfway along the underside of the whale. These grooves are less numerous (usually 16–20) and consequently more prominent than in other rorquals.
The stubby dorsal fin is visible soon after the blow when the whale surfaces, but disappears by the time the flukes emerge. Humpbacks have a 3 metres (9.8 ft) heart-shaped to bushy blow, or exhalation of water through the blowholes. Because Humpback Whales breathe voluntarily, researchers have said that it is possible that the whales shut off only half of the brain when sleeping. Early whalers also noted blows from humpback adults to be 10–20 feet (3.0–6.1 m) high.
Newborn calves are roughly the length of their mother's head. At birth, calves measure 20 feet (6.1 m) at 2 short tons (1.8 t) The mother, by comparison, is about 50 feet (15 m). They nurse for approximately six months, then mix nursing and independent feeding for possibly six months more. Humpback milk is 50% fat and pink in color. Some calves have been observed alone after arrival in Alaskan waters.
Females reach sexual maturity at the age of five, achieving full adult size a little later. Males reach sexual maturity at approximately 7 years of age. The humpback whale lifespan ranges from 45–100 years.[11]
Fully grown, the males average 15–16 metres (49–52 ft). Females are slightly larger at 16–17 metres (52–56 ft), and 40,000 kilograms (44 short tons); the largest recorded specimen was 19 metres (62 ft) long and had pectoral fins measuring 6 metres (20 ft) each.[12]
Females have a hemispherical lobe about 15 centimetres (5.9 in) in diameter in their genital region. This visually distinguishes males and females. The male's penis usually remains hidden in the genital slit. Male whales have distinctive scars on heads and bodies, some resulting from battles over females.
The varying patterns on the tail flukes are sufficient to identify individuals. Unique visual identification is not currently possible in most cetacean species (other exceptions include orcas and right whales), making the humpback a popular study species. A study using data from 1973 to 1998 on whales in the North Atlantic gave researchers detailed information on gestation times, growth rates, and calving periods, as well as allowing more accurate population predictions by simulating the mark-release-recapture technique (Katona and Beard 1982). A photographic catalogue of all known North Atlantic whales was developed over this period and is currently maintained by College of the Atlantic.[13] Similar photographic identification projects have begun in the North Pacific by SPLASH (Structure of Populations, Levels of Abundance and Status of Humpbacks), and around the world.
Females typically breed every two or three years. The gestation period is 11.5 months, yet some individuals have been known to breed in two consecutive years. The peak months for birth are January, February, July, and August. There is usually a 1-2 year period between humpback births. Humpback whales were thought to live 50–60 years, but new studies using the changes in amino acids behind eye lenses proved another baleen whale, the bowhead, to be 211 years old. This animal was taken by the Inuit off Alaska.
Recent research on humpback mitochondrial DNA reveals that groups that live in proximity to each other may represent distinct breeding pools.[14]
The humpback social structure is loose-knit. Typically, individuals live alone or in small, transient groups that disband after a few hours. These whales are not excessively social in most cases. Groups may stay together a little longer in summer to forage and feed cooperatively. Longer-term relationships between pairs or small groups, lasting months or even years, have rarely been observed. It is possible that some females retain bonds created via cooperative feeding for a lifetime. The humpback's range overlaps considerably with other whale and dolphin species — for instance, the minke whale. However, humpbacks rarely interact socially with them, though humpback calves in Hawaiian waters sometimes play with bottlenose dolphin calves.
Courtship rituals take place during the winter months, following migration toward the equator from summer feeding grounds closer to the poles. Competition is usually fierce, and unrelated males dubbed escorts by researcher Louis Herman frequently trail females as well as mother-calf dyads. Groups of two to twenty males gather around a single female and exhibit a variety of behaviors over several hours to establish dominance of what is known as a competitive group. Group size ebbs and flows as unsuccessful males retreat and others arrive to try their luck. Behaviors include breaching, spyhopping, lob-tailing, tail-slapping, fin-slapping, peduncle throws, charging and parrying. Less common "super pods" may number more than 40 males, all vying for the same female. (M. Ferrari et al.)
Whale song is assumed to have an important role in mate selection; however, scientists remain unsure whether song is used between males to establish identity and dominance, between a male and a female as a mating call, or both.
Both male and female humpback whales vocalize, however only males produce the long, loud, complex "songs" for which the species is famous. Each song consists of several sounds in a low register that vary in amplitude and frequency, and typically lasts from 10 to 20 minutes.[15] Humpbacks may sing continuously for more than 24 hours. Cetaceans have no vocal cords, so whales generate their song by forcing air through their massive nasal cavities.
Whales within a large area sing the same song. All North Atlantic humpbacks sing the same song, and those of the North Pacific sing a different song. Each population's song changes slowly over a period of years without repeating.[15]
Scientists are unsure of the purpose of whale song. Only males sing, suggesting that one purpose is to attract females. However, many of the whales observed to approach a singer are other males, and results in conflict. Singing may therefore be a challenge to other males.[16] Some scientists have hypothesized that the song may serve an echolocative function.[17] During the feeding season, humpbacks make altogether different vocalizations for herding fish into their bubble nets.[18]
All these behaviors also occur in absence of potential mates. This indicates that they are probably a more general communication tool. Scientists hypothesize that singing may keep migrating populations connected. (Ferrari, Nicklin, Darling, et al.) Some observers report that singing begins when competition for a female ends.[19]
Humpback whales have also been found to make a range of other social sounds to communicate such as "grunts", "groans", "thwops", "snorts" and "barks".[20]
Humpbacks feed primarily in summer and live off fat reserves during winter.[21] They feed only rarely and opportunistically in their wintering waters. The humpback is an energetic hunter, taking krill and small schooling fish such as Atlantic herring, Atlantic salmon, capelin, and American sand lance as well as Atlantic mackerel, pollock, and haddock in the North Atlantic.[22][23][24] Krill and copepods have been recorded as prey species in Australian and Antarctic waters.[25] Humpbacks hunt by direct attack or by stunning prey by hitting the water with pectoral fins or flukes.
The humpback has the most diverse feeding repertoire of all baleen whales.[26] Its most inventive technique is known as bubble net feeding: a group of whales swims in a shrinking circle blowing bubbles below a school of prey. The shrinking ring of bubbles encircles the school and confines it in an ever-smaller cylinder. This ring can begin at up to 30 metres (98 ft) in diameter and involve the cooperation of a dozen animals. Using a crittercam attached to a whale's back it was discovered that some whales blow the bubbles, some dive deeper to drive fish toward the surface, and others herd prey into the net by vocalizing.[27] The whales then suddenly swim upward through the 'net', mouths agape, swallowing thousands of fish in one gulp. Plated grooves in the whale's mouth allow the creature to easily drain all the water that was initially taken in. Solitary humpbacks have also been observed employing this technique.
Given scarring records, killer whales are thought to prey upon juvenile humpbacks, though this has never been witnessed. The result of these attacks is generally nothing more serious than some scarring of the skin, but it is likely that young calves are sometimes killed.[28]
Humpbacks inhabit all major oceans, in a wide band running from the Antarctic ice edge to 77° N latitude, though not in the eastern Mediterranean or the Baltic Sea.
Humpbacks are migratory, spending summers in cooler, high-latitude waters and mating and calving in tropical and subtropical waters.[15] An exception to this rule is a population in the Arabian Sea, which remains in these tropical waters year-round.[15] Annual migrations of up to 25,000 kilometres (16,000 mi) are typical, making it one of the mammal's best-traveled species.
A large population spreads across the Hawaiian islands every winter, ranging from the island of Hawaii in the south to Kure Atoll in the north.[29] A 2007 study identified seven individuals wintering off the Pacific coast of Costa Rica as having traveled from the Antarctic—around 8,300 kilometres (5,200 mi). Identified by their unique tail patterns, these animals made the longest documented mammalian migration.[30]
In Australia, two main migratory populations have been identified, off the west and east coast respectively. These two populations are distinct, with only a few females in each generation crossing between the two groups.[31]
One of the first attempts to hunt humpbacks was made by John Smith in 1614 off the coast of Maine. Opportunistic hunting is likely to have occurred long before. By the 18th century, they had become a common target for whalers.
By the 19th century, many nations (the United States in particular), were hunting the animal heavily in the Atlantic Ocean, and to a lesser extent in the Indian and Pacific Oceans. It was, however, the late 19th century introduction of the explosive harpoon that allowed whalers to accelerate their take. This, along with hunting in the Antarctic Ocean beginning in 1904, sharply reduced whale populations.
It is estimated that during the 20th century, at least 200,000 humpbacks were taken, reducing the global population by over 90%, with North Atlantic populations estimated to have dropped to as low as 700 individuals.[32] In 1946, the International Whaling Commission was founded to oversee the whaling industry. They imposed rules and regulations for hunting whales and set open and closed hunting seasons. To prevent extinction, the International Whaling Commission banned commercial humpback whaling in 1966. By that time the population had been reduced to around 5,000.[33] That ban is still in force.
Prior to commercial whaling, populations could have reached 125,000. North Pacific kills alone are estimated at 28,000.[8] The full toll is much higher. It is now known that the Soviet Union was deliberately under-recording its catches; the Soviet catch was reported at 2,820 whereas the true number is now believed to be over 48,000.[34]
As of 2004, hunting of humpback whales is restricted to a few animals each year off the Caribbean island Bequia in the nation of St. Vincent and the Grenadines.[26] The take is not believed to threaten the local population.
Japan had planned to kill 50 humpbacks in the 2007/08 season under its JARPA II research program, starting in November 2007. The announcement sparked global protests.[35] After a visit to Tokyo by the chairman of the IWC, asking the Japanese for their co-operation in sorting out the differences between pro- and anti-whaling nations on the Commission, the Japanese whaling fleet agreed that no humpback whales would be caught for the two years it would take for the IWC to reach a formal agreement.[36]
There are at least 80,000 humpback whales worldwide, with 18,000-20,000 in the North Pacific,[37] about 12,000 in the North Atlantic,[38] and over 50,000 in the Southern Hemisphere,[39] down from a pre-whaling population of 125,000.[8]
This species is considered "least concern" from a conservation standpoint, as of 2008. This is an improvement from vulnerable in the prior assessment. Most monitored stocks of humpback whales have rebounded well since the end of commercial whaling[2][40], such as the North Atlantic where stocks are now believed to be approaching pre-hunting levels. However, the species is considered endangered in some countries, including the United States.[41][42] The United States initiated a status review of the species on August 12, 2009, and is seeking public comment on potential changes to the species listing under the U.S. Endangered Species Act.[43] Areas where population data is limited and the species may be at higher risk include the Arabian Sea, the western North Pacific Ocean, the west coast of Africa and parts of Oceania.[2]
Today, individuals are vulnerable to collisions with ships, entanglement in fishing gear, and noise pollution.[2] Like other cetaceans, humpbacks can be injured by excessive noise. In the 19th century, two humpback whales were found dead near sites of repeated oceanic sub-bottom blasting, with traumatic injuries and fractures in the ears.[44]
Once hunted to the brink of extinction, the humpback has made a dramatic comeback in the North Pacific. A 2008 study estimates that the humpback population that hit a low of 1,500 whales before hunting was banned worldwide, has made a comeback to a population of between 18,000 and 20,000.[45]
Saxitoxin, a paralytic shellfish poisoning (PSP) from contaminated mackerel has been implicated in humpback whale deaths.[46]
The United Kingdom, among other countries, designated the humpback as a priority species under the national Biodiversity Action Plan.
The sanctuary provided by U.S. National Parks such as Glacier Bay National Park and Preserve and Cape Hatteras National Seashore, among others, have also become major factors in sustaining populations.[47]
Although much was learned about humpbacks from whaling, migratory patterns and social interactions were not well understood until two studies by R. Chittleborough and W. H. Dawbin in the 1960s.[48] Roger Payne and Scott McVay made further studies of the species in 1971.[49] Their analysis of whale song led to worldwide media interest and convinced the public mind that whales were highly intelligent, aiding the anti-whaling advocates.
In August 2008, the IUCN changed humpback's status from Vulnerable to Least Concern, although two subpopulations remain endangered.[50]
The United States is considering listing separate humpback populations, so that smaller groups, such as North Pacific humpbacks, which are estimated to number 18,000-20,000 animals, might be delisted. This is made difficult by humpback's extraordinary migrations, which can extend the 5,157 miles (8,299 km) from Antarctica to Costa Rica.[14]
Humpback whales are generally curious about objects in their environment. Some individuals, referred to as "friendlies", approach whale-watching boats closely, often staying under or near the boat for many minutes. Because humpbacks are often easily approachable, curious, easily identifiable as individuals, and display many behaviors, they have become the mainstay of whale-watching tourism in many locations around the world. Hawaii has used the concept of "eco tourism" to use the species without killing them. This whale watching business attracts 1 million visitors a year, which results in a profit of $80 million.
There are many commercial whale-watching operations on both the humpback's summer and winter ranges:
| North Atlantic | North Pacific | Southern Hemisphere | |
|---|---|---|---|
| Summer | New England, Nova Scotia and Newfoundland, the northern St. Lawrence River, the Snaefellsnes peninsula in the west of Iceland | California, Alaska, Oregon, Washington, British Columbia | Antarctica, Bahía Solano and Nuquí in Colombia |
| Winter | Samaná Province of the Dominican Republic, the Bay of Biscay France, | Hawaii, Baja, the Bahía de Banderas off Puerto Vallarta | Sydney, Byron Bay north of Sydney, Hervey Bay north of Brisbane, North and East of Cape Town, New Zealand, the Tongan islands, |
As with other cetacean species, however, a mother whale is generally extremely protective of her infant, and places herself between any boat and her calf before moving quickly away from the vessel. Skilled tour operators avoid stressing the mother.
A presumably albino humpback whale that travels up and down the east coast of Australia has become famous in the local media, on account of its extremely rare all-white appearance. Migaloo is the only known all-white humpback whale in the world.[51] First sighted in 1991 and believed to be 3–5 years old at that time, Migaloo is a word for "white fella" from one of the languages of the Aboriginals, the Indigenous Australians. Speculation about Migaloo's sex was resolved in October 2004 when researchers from Southern Cross University collected sloughed skin samples from Migaloo as he migrated past Lennox Head, and subsequent genetic analysis of the samples proved he is a male. Because of the intense interest, environmentalists feared that he was becoming distressed by the number of boats following him each day. In response, the Queensland and New South Wales governments introduce legislation each year to create a 500 m (1600 ft) exclusion zone around the whale. Recent close up pictures have shown Migaloo to have skin cancer and/or skin cysts as a result of his lack of protection from the sun.[52]
In 2006, a white calf was spotted with a normal humpback mother in Byron Bay, New South Wales.[53]
One of the most notable humpback whales is Humphrey the Whale, twice-rescued by The Marine Mammal Center and other concerned groups in California.[54][55] In 1985, Humphrey swam into San Francisco Bay and then up the Sacramento River towards Rio Vista.[56] Five years later, Humphrey returned and became stuck on a mudflat in San Francisco Bay immediately north of Sierra Point below the view of onlookers from the upper floors of the Dakin Building. He was pulled off the mudflat with a large cargo net and the help of the Coast Guard. Both times he was successfully guided back to the Pacific Ocean using a "sound net" in which people in a flotilla of boats made unpleasant noises behind the whale by banging on steel pipes, a Japanese fishing technique known as "oikami." At the same time, the attractive sounds of humpback whales preparing to feed were broadcast from a boat headed towards the open ocean.[57] Since leaving the San Francisco Bay in 1990 Humphrey has been seen only once, at the Farallon Islands in 1991.
A humpback whale mother and calf captivated the San Francisco Bay Area in May 2007.[58] This pair appeared to have gotten lost on their Northern migration, swam into the bay and up the Sacramento River as far as the Port of Sacramento. First spotted on 13 May, the whales inspired intense news coverage and were named Delta and Dawn. Whale fans became worried as the whales, both injured with what were possibly cuts caused by boat propellers, continued their stay in the brackish waters, despite efforts to get them to return to the sea. Unexpectedly, on 20 May they headed back towards the bay, but they tarried near the Rio Vista bridge for 10 days. Finally, on Memorial Day weekend, they left Rio Vista, California; passing Tuesday night, 29 May, through the Golden Gate out to the Pacific Ocean.
Mister Splashy Pants is a humpback in the south Pacific Ocean. It's being tracked with a satellite tag by Greenpeace as a part of its Great Whale Trail Expedition.[59] The whale's name was chosen in an online poll that garnered attention from several websites, including Boing Boing and Reddit.[60] The name "Mister Splashy Pants" received over 78% of the votes.[61]
Colin was the name given to a presumably abandoned starving humpback calf that was discovered in August 2008 at Pittwater, north of Sydney, Australia. It attempted to suckle from moored boats to obtain food.[62][63] Despite attempts to reunite the calf with whale pods by luring it out to sea, it returned to Pittwater. Opinion was divided on how best to handle the situation, with some advocating feeding artificial milk formula to the calf, and others advocating euthanasia.[64]
Colin was euthanised on 22 August 2008 due to his deteriorating condition.[65] The calf's plight gained media attention as far afield as the United States,[66] United Kingdom,[67] Italy,[68] Netherlands,[69] Russia,[70] Canada[71] and New Zealand.[72]
A subsequent autopsy found that Colin was terminally ill with an emaciated pancreas, ulcers of the stomach and oesophagus, intestinal erosion and infected shark bites.[73] The calf was estimated to be only 7 to 10 days old and must have been separated from its mother shortly after birth.[74]
On 12 September 2009, a humpback was seen in the London Thames for the first time ever. [75] Two days later on 14 September near Dartford bridge the humpback was found beached and dead. It was 9.5 m long and a young male. Initial examination of the body suggested death had been by starvation, without any explanation of why this had occurred. Experts suggested that such events as these indicated the expansion of the areas colonised by humpbacks. [76]
George and Gracie were a pair of fictional humpbacks which featured prominently in Star Trek IV: The Voyage Home. In the film, Earth is threatened by large object that transmits a signal disabling the global power system and causing extreme weather patterns to develop. Spock determines the alien signal matches the song of humpback whales, extinct on Earth since the mid-21st century (at least 200 years). The crew devises a plan to go back in time, before the extinction, and return with a whale. Arriving in the late 20th century, Kirk and Spock are able to quickly discover a pair of humpback whales, "George" and "Gracie", at the Cetacean Institute, an aquarium devoted exclusively to whales, and are told by the Institute's whale expert, Dr. Gillian Taylor, that the whales are shortly going to be released into the wild, making the pair ideal for their needs. Despite some upsets and the threat of whalers, the crew is able to return to the future, splashing down into San Francisco Bay, where Kirk releases the whales from the cargo hold. The whales respond to the alien signal, causing the object to restore Earth to its normal condition and to return to the depths of outer space.
Industrial Light & Magic created the visual effects. Most shots of the humpback whales were scale models shot at their studio or life-size animatronics shot at Paramount.[77] However, some of the shots, including a scene of a whale breaching, are stock footage of actual animals.