Humpback whale facts for kids
Quick facts for kids Humpback whale |
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Megaptera
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novaeangliae
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A humpback whale (Megaptera novaeangliae) is a large baleen whale with long flippers and a knobbly head. They can be found in every ocean.
They can grow to 15–16 m (49–52 ft) long and weigh up to 40 metric tons.
Contents
Anatomy
Humpbacks can easily be identified by their stocky body, obvious hump, black dorsal coloring and elongated pectoral fins. The head and lower jaw are covered with knobs called tubercles, which are hair follicles and are characteristic of the species. The fluked tail, which typically rises above the surface when diving, has wavy trailing edges.
Humpbacks have 270 to 400 darkly colored baleen plates on each side of their mouths. The plates measure from 18 in (46 cm) in the front to about 3 ft (0.91 m) in the back, behind the hinge.
Ventral grooves run from the lower jaw to the umbilicus, about halfway along the underside of the body. These grooves are less numerous (usually 14–22) than in other rorquals, but are fairly wide.
The female has a hemispherical lobe about 15 cm (5.9 in) in diameter in her genital region. This visually distinguishes males and females. The male's penis usually remains hidden in the genital slit.
Size
Fully grown males average 13–14 m (43–46 ft). Females are slightly larger at 15–16 m (49–52 ft); one large recorded specimen was 19 m (62 ft) long and had pectoral fins measuring 6 m (20 ft) each. The largest humpback on record, according to whaling records, was a female killed in the Caribbean; she was 27 m (89 ft) long with a weight of 90 metric tons (99 short tons), although the reliability of this information is unconfirmed due to illogicality of the record. The largest measured by the scientists of the Discovery Committee were a female 14.9 m (49 ft) and a male 14.75 m (48.5 ft), although this was out of a sample size of only 63 whales. Body mass typically is in the range of 25–30 metric tons (28–33 short tons), with large specimens weighing over 40 metric tons (44 short tons).
Newborn calves are roughly the length of their mother's head. At birth, calves measure 6 m (20 ft) at 2 short tons (1.8 t). They nurse for about six months, then mix nursing and independent feeding for possibly six months more. Humpback milk is 50% fat and pink in color.
Females reach sexual maturity at age five, achieving full adult size a little later. Males reach sexual maturity around seven years of age.
Fins
The long black and white tail fin can be up to a third of body length. Several hypotheses attempt to explain the humpback's pectoral fins, which are proportionally the longest fins of any cetacean. 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 possibly supported this adaptation.
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Identifying individuals
The varying patterns on the tail flukes distinguish individual animals. 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. A photographic catalogue of all known North Atlantic whales was developed over this period and is maintained by College of the Atlantic. Similar photographic identification projects operate around the world.
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Humpback whale skeleton on display at The Museum of Osteology, Oklahoma City, Oklahoma
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A humpback whale tail displaying wavy rear edges
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A tail from a different individual—the tail of each humpback whale is visibly unique.
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Individual identification in Vava'u, Tonga
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Humpback whale skeleton of "Snow" on display at Glacier Bay National Park and Preserve
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Behavior
The lifespan of rorquals ranges from 45 to 100 years.
Interactions
The humpback social structure is loose-knit. Typically, individuals live alone or in small, transient groups that disband after a few hours. Groups may stay together 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. Some females possibly retain bonds created via cooperative feeding for a lifetime. Humpback whales often leap out of the water, a behaviour known as "breaching", and slap the water with their fins or tails
Courtship and reproduction
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. Unrelated males, dubbed escorts, frequently trail females, as well as cow-calf pairs. Males gather into "competitive groups" around a female and fight for the right to mate with her. Group size ebbs and flows as unsuccessful males retreat and others arrive. Behaviors include breaching, spyhopping, lob-tailing, tail-slapping, pectoral fin-slapping, peduncle throws, charging and parrying.
Whale song is thought to have an important role in mate selection; however, they may also be used between males to establish dominance. Polygamy has been observed in humpback whales, with the females having multiple male partners throughout their lifespan.
Females typically breed every two or three years. The gestation period is 11.5 months. The peak months for birth are January, February (northern hemisphere), July and August (southern hemisphere). Females wait for one to two years before breeding again. Recent research on mitochondrial DNA reveals that groups living in proximity to each other may represent distinct breeding pools.
Interspecies interactions
Humpbacks are a friendly species that interact with other cetacean species such as bottlenose dolphins. Right whales interact with humpbacks. These behaviors have been recorded in all oceans. Records of humpback and southern right whales demonstrating what were interpreted to be mating behaviors have been documented off the Mozambique and Brazilian coasts. Humpback whales appear in mixed groups with other species, such as the blue, fin, minke, gray and sperm whales. Interaction with gray, fin, and right whales have been observed.
Teams of researchers observed a male humpback whale singing an unknown type of song and approaching a fin whale at Rarotonga in 2014. One individual was observed playing with a bottlenose dolphin in Hawaiian waters. Recently, incidents of humpback whales protecting other species of animals such as seals and other whales from killer whales has been documented and filmed.
Studies of such incidents indicate that the phenomenon is species-wide and global, with incidents being recorded at various locations across the world. In September 2017 in Rarotonga, the Cook Islands, two adult humpback whales were observed protecting snorkeler and whale biologist Nan Hauser from a 4.5 m (15 ft) tiger shark, with one whale pushing the woman away from the shark while the other used its tail to block the predator's advances. This may be the first recorded incidence of humpback whales acting protective over a human.
Song
Both male and female humpback whales vocalize, but only males produce the long, loud, complex "song" for which the species is famous. Each song consists of several sounds in a low register, varying in amplitude and frequency and typically lasting from 10 to 20 minutes. Individuals may sing continuously for more than 24 hours. Cetaceans have no vocal cords, instead, they produce sound via a larynx like structure found in the throat, the mechanism of which has not as of yet been clearly identified. Whales do not have to exhale to produce sound.
Whales within a large area sing a single song. All North Atlantic humpbacks sing the same song, while those of the North Pacific sing a different song. Each population's song changes slowly over a period of years without repeating.
Scientists are unsure of the purpose of whale songs. Only males sing, suggesting one purpose is to attract females. However, many of the whales observed to approach a singer are other males, often resulting in conflict. Singing may, therefore, be a challenge to other males. Some scientists have hypothesized the song may serve an echolocative function.
During the feeding season, humpbacks make unrelated vocalizations for herding fish into their bubble nets.
Humpback whales make other sounds to communicate, such as grunts, groans, snorts and barks.
Breathing
Whales are air-breathing mammals who must surface to get the air they need. The stubby dorsal fin is visible soon after the blow (exhalation) when the whale surfaces, but disappears by the time the flukes emerge. Humpbacks have a 3 m (9.8 ft), heart-shaped to bushy blow through the blowholes.
They do not generally sleep at the surface, but they must continue to breathe. Possibly only half of their brain sleeps at one time, with one half managing the surface-blow-dive process without awakening the other half.
Range and habitat
Humpbacks inhabit all major oceans, in a wide band running from the Antarctic ice edge to 77° N latitude. The four global populations are North Pacific, Atlantic, Southern Ocean and Indian Ocean populations. These populations are distinct. Although the species has cosmopolitan distribution and is usually not considered to cross the equator line, seasonal observations at Cape Verde suggest possible interactions among populations from both hemispheres. Aside from the Arabian Sea group, year-round presences have been confirmed among British and Norwegian waters. Parts of wintering grounds around the globe have been poorly studied or being undetected, such as around Pitcairn Islands, Northern Mariana Islands (e.g. Marpi and CK Reefs vicinity to Saipan ), Daitō Islands, Volcano Islands, Pasaleng Bay, Trindade and Martin Vaz, Mauritius, Aldabra, and so on.
Whales were once uncommon in the Mediterranean and the Baltic Sea, but have increased their presence in both waters as global populations have recovered. Recent increases within the Mediterranean basin, including re-sightings, indicate that more whales may migrate into the inland sea in the future, not only for wintering but also for feeding. Humpbacks are also showing signs of re-expanding into former ranges, such as Scotland, Skagerrak and Kattegat, as well as Scandinavian fjords such as Kvænangen, where they had not been observed for decades.
In the North Atlantic, feeding areas range from Scandinavia to New England. Breeding occurs in the Caribbean and Cape Verde. In the South Atlantic and Indian Oceans, whales may breed off Brazil, as well the coasts of central, southern and southeastern Africa (including Madagascar). Whale visits into Gulf of Mexico have been infrequent, but occurred in the gulf historically. In the South Atlantic, about 10% of world population of the species possibly migrate to the Gulf of Guinea. Comparison of songs between those at Cape Lopez and Abrolhos Archipelago indicate that trans-Atlantic mixings between western and southeastern populations occur.
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. These animals feed in areas ranging from the coast of California to the Bering Sea. Humpbacks were first observed in Hawaiian waters in the mid-19th century and might have gained a dominance over North Pacific right whales, as the right whales were hunted to near-extinction.
A 2007 study identified seven individuals then wintering off the Pacific coast of Costa Rica as having traveled from the Antarctic—around 8,300 km (5,200 mi). Identified by their unique tail patterns, these animals made the longest documented mammalian migration. In Australia, two main migratory populations were identified, off the west and east coasts. These two populations are distinct, with only a few females in each generation crossing between the two groups.
In Panama and Costa Rica, humpback whales come from both the Southern Hemisphere (July–October with over 2,000 whales) and the Northern Hemisphere (December–March numbering about 300.) South Pacific populations migrating off mainland New Zealand, Kermadec Islands, and Tasmania are increasing, but less rapidly than in Australian waters because of illegal whaling by the Soviet Union in the 1970s.
Some recolonizing habitats are confirmed, especially in the North and South Atlantic (e.g. English and Irish coasts, English Channel to coasts in the north such as the North Sea and Wadden Sea, where the first confirmed sighting since 1755 was made in 2003, South Pacific (e.g. New Zealand coasts and Niue), pelagic islands of Chile such as Isla Salas y Gómez and Easter Island, where possibilities of undocumented wintering grounds have been considered, southern fiords of Chile and Peru (e.g. Gulf of Penas, Strait of Magellan, Beagle Channel and in Asia. Areas in the Philippines such as the Babuyan Islands, Cagayan (the first modern mortality of the species in the nation was in 2007), Calayan and Pasaleng Bay, the Ryukyu Islands, the Volcano Islands in Japan and the Northern Mariana Islands recently again became stable/growing wintering grounds while the Marshall Islands, Vietnamese, Taiwanese and Chinese coasts show slow or no obvious recovery.
Whales again migrate off Japanese archipelagos and into the Sea of Japan.
Since November 2015, whales gather around Hachijō-jima, far north from the known breeding areas in the Bonin Islands. All breeding activities except for giving births had been confirmed as of January, 2016. That makes Hachijo-jima the northernmost breeding ground in the world, north of breeding grounds such as Amami Ōshima, Midway Island, and Bermuda.
Arabian Sea population
A non-migratory population in the Arabian Sea remains there year-round. More typical annual migrations cover up to 25,000 km (16,000 mi), making it one of the most-traveled mammalian species. Genetic studies and visual surveys indicate that the Arabian group is the most isolated of all humpback groups and is the most endangered, numbering possibly fewer than 100 animals. Within Arabian Sea, Masirah Island and Gulf of Masirah, Halaniyat Islands and Kuria Muria Bay are hot spots for the species.
Whales were historically common in continental and marginal waters such as Hallaniyat Islands, along Indian coasts, Persian Gulf and Gulf of Aden and recent migrations into the gulf including by cow-calf pairs. It is unknown whether whales seen in the Red Sea originate in this population, however sightings increased since in 2006 even in the northern part of the sea such as in Gulf of Aqaba. Individuals may reach the Maldives, Sri Lanka, or further east. Humpbacks have been considered rather vagrant into Persian Gulf, however new studies indicate more regular presences can be expected.
Origins of whales occurring at Maldives are not clear either from Arabian or south Pacific populations, and overlaps are possible.
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Arabian Sea Humpback whales in Dhofar, Oman
Feeding and predation
Humpbacks feed primarily in summer and live off fat reserves during winter. They feed only rarely and opportunistically in their wintering waters. The humpback is an energetic hunter, taking krill and small schooling fish such as juvenile Atlantic and Pacific salmon, herring, capelin and American sand lance, as well as Atlantic mackerel, pollock and haddock in the North Atlantic. They have been documented opportunistically feeding near fish hatcheries in Southeast Alaska, feasting on salmon fry released from the hatcheries. Krill and copepods are prey species in Australian and Antarctic waters. Humpbacks hunt by direct attack or by stunning prey by hitting the water with pectoral fins or flukes.
Bubble net
The humpback has the most diverse hunting repertoire of all baleen whales. 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 near 30 m (98 ft) in diameter and involve the cooperation of a dozen animals. Using a crittercam attached to a whale's back, researchers found that some whales blow the bubbles, some dive deeper to drive fish toward the surface and others herd prey into the net by vocalizing. The whales then suddenly swim upward through the "net", mouths agape, swallowing thousands of fish in one gulp. Pleated grooves in the whale's mouth allow the creature to easily drain the water initially taken in, filtering out the prey.
So-called lobtail feeding was observed in the North Atlantic. This technique involves the whale slapping the surface of the ocean with its tail between one and four times before creating the bubble net. Using network-based diffusion analysis, the study authors argued that these whales learned the behavior from other whales in the group over a period of 27 years in response to a change in the primary form of prey.
Killer whale predation
Visible scars indicate that killer whales can prey upon juvenile humpbacks, though until recently hunting had never been witnessed and attacks were assumed to be superficial in nature. However, a 2014 study off Western Australia observed that when available in large numbers, young humpbacks can be attacked and sometimes killed by orcas. Moreover, mothers and (possibly related) adults escort neonates to deter such predation. The suggestion is that when humpbacks suffered near-extinction during the whaling era, orcas turned to other prey, but are now resuming their former practice. There is evidence that humpback whales will defend against or attack killer whales who are attacking either humpback calves or juveniles as well as members of other species.
Relation to humans
Whaling
Humpback whales were hunted as early as the 18th century. 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. The late-19th-century introduction of the explosive harpoon allowed whalers to accelerate their take. This, along with hunting in the Antarctic Ocean beginning in 1904, sharply reduced whale populations. During the 20th century, over 200,000 humpbacks were taken, reducing the global population by over 90%. North Atlantic populations dropped to as low as 700 individuals.
Ban
In 1946, the International Whaling Commission (IWC) was founded to oversee the industry. They imposed hunting regulations and created hunting seasons. To prevent extinction, IWC banned commercial humpback whaling in 1966. By then, the global population had been reduced to around 5,000. The ban has remained in force since 1966.
Prior to commercial whaling, populations could have reached 125,000. North Pacific kills alone are estimated at 28,000. The Soviet Union deliberately under-recorded its catches; the Soviets reported catching 2,820 between 1947 and 1972, but the true number was over 48,000.
As of 2004, hunting was restricted to a few animals each year off the Caribbean island of Bequia in the nation of St. Vincent and the Grenadines. 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. The announcement sparked global protests. After a visit to Tokyo by the IWC chair asking the Japanese for their co-operation in sorting out the differences between pro- and antiwhaling nations on the commission, the Japanese whaling fleet agreed to take no humpback whales during the two years it would take to reach a formal agreement.
In 2010, the IWC authorized Greenland's native population to hunt a few humpback whales for the following three years.
In Japan, humpback, minkes, sperm and many other smaller Odontoceti, including critically endangered species such as North Pacific right, western gray and northern fin, have been targets of illegal captures. The hunts use harpoons for dolphin hunts or intentionally drive whales into nets, reporting them as cases of entanglement. Humpback meat can be found in markets. In one case, humpbacks of unknown quantities were illegally hunted in the Exclusive Economic Zones of anti-whaling nations such as off Mexico and South Africa.
Whale-watching
Whale watching is the leisure activity of observing humpbacks in the wild. Participants watch from shore or on touring boats. Humpbacks are generally curious about nearby objects. Some individuals, referred to as "friendlies", approach whale-watching boats closely, often staying under or near the boat for many minutes.
Because humpbacks are typically easily approachable, curious, identifiable as individuals and display many behaviors, they have become the mainstay of whale tourism around the world. Hawaii has used the concept of "ecotourism" to benefit from the species without killing them. This business brings in revenue of $20 million per year for the state's economy.
Images for kids
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Young whale with blowholes visible
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Female humpback whale with her calf
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Spectrogram of humpback whale vocalizations: detail is shown for the first 24 seconds of the 37-second recording "Singing Humpbacks".
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Humpback whales taken by whalers off Vancouver Island, early 20th century
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A dead humpback washed up near Big Sur, California
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Whale watching off Massachusetts
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Professor John Struthers about to dissect the Tay Whale, Dundee, photographed by George Washington Wilson in 1884
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Possible Migaloo sighted off the Royal National Park
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See also
In Spanish: Megaptera novaeangliae para niños
