Humpback Whales, Megaptera novaeangliae
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Description & Behavior
Humpback whales, Megaptera novaeangliae (Borowski, 1781), like all rorquals (blue whales, Bryde's whales, fin whales, minke whales, and sei whales) are long, slender whales that are much more streamlined than other large whales. They have pointed snouts, paired blowholes, and broad, flat rostrums (upper part of their head). Their throat grooves, in addition to streamlining their shape, allow their throat area (called the cavum vent-rale) to expand during feeding. Their baleen plates are broad and short, and their left and right rows are continuous. Their dorsal fin is falcate (curved).
All members of the Order Cetacea (includes all whales, toothed and those using baleen) are believed to have evolved from terrestrial hoofed mammals like cows, camels, and sheep some 45 million years ago - that's about 40 million years before humans! Recent comparisons of some milk protein genes (beta-casein and kappa-casein) have confirmed this relationship and have suggested that the closest land-bound living relative of whales may be the hippopotamus. Throughout their evolution, cetaceans have become perfectly suited to an aquatic environment, and are virtually incapable of leaving it. Cetaceans illustrate an example of adaptive radiation among mammals. Adaptive radiation allows mammals as a group to effectively inhabit the land, the sea, and the air through the development of special adaptations needed to survive in each of these environments. Members of the Order Cetacea have undergone a number of changes or adaptations needed to fare well in their watery home: their bodies have become streamlined for efficient movement through the water; their forelimbs have been modified into flippers which aid them in steering; their hind limbs have disappeared almost completely; their tail has become broadened horizontally and consists of two large flukes which propel them powerfully through the water by moving up and down, rather than side-to-side like a fish; in place of hair they have developed a thick layer of fat called blubber under their skin that insulates them from the cold and provides buoyancy; and the position of their nostrils has shifted to the top of their head creating a blowhole that allows them to effectively come to the surface for air. A whale's blowhole generally reaches the surface before the rest of its body.
Adapting to the Sea
In addition, a number of other changes have taken place to help whales adapt to life in the sea. Many of these changes are related to the position and abilities of their sensory organs, as life in the water is not the same as life on the land. Sound and light travel differently in water than they do in the air. As a result, whales have developed unique ways of hearing and seeing. Hearing in particular is highly developed in whales, so much so that they depend on it in the same way that we depend on the combination of our eyes, ears and nose to understand the world around us. Many of the whale's sensory and reproductive organs have been internalized to reduce drag while swimming. For example, whales do not have external ears, but rely on an internal system of air sinuses and bones to detect sounds. Changes in their reproductive and parental behaviors have also taken place, enabling whales to provide optimum care for their young in the cold, large ocean. Along with these differences, cetaceans do, however, possess many of the same physiological systems such as circulatory, digestive, respiratory, and nervous systems as the land mammals from which they evolved. For instance, many species possess multi-chambered stomachs even though there is no obvious advantage to having such an arrangement as whales do not chew cud!
The heads of humpback whales are broad and rounded when viewed from above, but slim in profile. Their body is not as streamlined as other rorquals, but is quite round, narrowing to a slender peduncle (tail stock). The top of their head and lower jaw have rounded, bump-like knobs, each containing at least one stiff hair. The purpose of these hairs is not known, though they may provide the whale with a sense of "touch." They have between 20-35 ventral (underside) grooves which extend slightly beyond their navel.
Adult male humpbacks measure between 12.2-14.6 m, adult females measure 13.7-15.2 m. They weigh 22,680-36,287 kg. Their scientific name is Megaptera noveangliae. This means "giant wings", which refers to their large front flippers that can reach a length of 4.6 m—about one-third of the animal's entire body length. Their body is black on the dorsal (upper) side, and mottled black and white on their ventral (under) sides. This color pattern extends to their flukes (tails). When humpback whales sound (go into long or deep dives) they usually throw their fluke upward, exposing their black and white patterned undersides. This pattern is distinctive to each whale. Their flippers range from all white to all black. The shape and color patterns on humpback whales' dorsal fins and flukes are as individual as fingerprints in humans.
Humpbacks have become renowned for their various acrobatic displays. In fact, their common name "humpback" refers to the high arch of their backs when they dive. About 2/3 back on their body is an irregularly shaped dorsal fin. Their flippers are very long, between 1/4 and 1/3 the length of their body, and have large knobs on their leading edges. Their fluke or tail fin, which can be 5.5 m wide, is serrated and pointed at the tips. One of the humpback's more spectacular behaviors is the breach. Breaching is a true leap where a whale generates enough upward force with its powerful flukes to lift approximately 2/3 of its body out of the water. A breach may also involve a twisting motion, when the whale twists its body sideways as it reaches the height of the breach. Researchers are not yet certain why whales breach, but believe that it may be related to courtship or play activity. Some behaviors such as headlunging, which occurs when one whale thrusts its head forcefully towards another whale in a threatening manner, are believed to be aggressive behaviors meant to ward off competitors. Males display this behavior most often when trying to gain access to females. Many other behaviors including fluke slaps, flipper slaps, and headslaps have also been characterized, although their apparent functions are as of yet unknown.
The "songs" of humpbacks are made up of complex vocal patterns. All whales within a given area and season seem to use the same songs. However, the songs appear to change from one breeding season to the next. Scientists believe that only male humpbacks sing. While the purpose of the songs is not known exactly, many scientists think that males sing to attract mates, or to communicate among other males of the pod.
A pod refers to a social group of whales. In Hawaii, humpback whales typically belong to pods consisting of 2-3 individuals, although pods as large as 15 individuals have been sighted. Scientists feel that whales belong to certain pods for relatively short periods of time. One type of pod that is especially interesting is the cow-calf pod. A cow-calf pod represents the longest association between individual whales. In this type of pod, the mother whale, the cow, remains with her calf for a year during which time she nurses the young whale. In may instances, cow-calf pods are accompanied by another adult known as an escort. Escorts can be of either sex, but are most often reported to be males. Escorts do not remain in the cow-calf pod for long periods of time, usually for only a few hours. There have been no reported sightings of whale pods which contain more than one calf, indicating that each young whale is given a great deal of individual attention and care. This fact, together with the fact that the normal breeding-cycle of a humpback whale is two years, helps to explain why recovery of humpback whale populations progresses so slowly.
World Range & Habitat
Humpback whales, Megaptera novaeangliae, are found in all of the world's oceans, although they generally prefer near shore and near-island habitats for both feeding and breeding. A recent world population for the species was estimated to be around 60,000 individuals (6,000 - 8,000 in the North Pacific, 12,000 in the North Atlantic, and approximately 40,000 in the Southern Hemisphere) or about 30-35% of their original population before whaling, and can be divided into groups based on the regions in which they live. One group found in the North Pacific, in the waters off Alaska, is estimated to consist of about 2,000 individuals. A large percentage of this population migrates to the Hawaiian islands during the winter months, November through May, each year. The round-trip distance they travel during this annual migration is approximately 9,656 km, one of the longest migration distances of any animal species. During their stay in Hawaii, they do not feed, but rely upon energy stored in their blubber. Instead of feeding, the whales devote most of their time to mating and bearing their calves.
In the Atlantic, humpbacks migrate from Northern Ireland and Western Greenland to the West Indies (including the Gulf of Mexico).
In the Pacific they migrate generally from the Bering Sea to Southern Mexico. Another known small population migrates from their feeding grounds in Antarctic waters to their Tongan breeding grounds. These whales form part of an Antarctic feeding population south of New Zealand and Australia, but little is known about the migration path of this small population and their movements between the Southwestern Pacific Islands. This "Tongan tribe" is even "more" special than other groups of humpbacks—it is the last group to be hunted, with the fewest survivors and is the least understood. Hunted until 1979 for their oil, meat and bone, scientists now pursue humpbacks for observation, while whale watchers seek them for the thrill and privilege of seeing these magnificent creatures in their natural habitat.
Feeding Behavior (Ecology)
Humpback whales feed on krill, small shrimp-like crustaceans, and various kinds of small fish. Each whale eats up to 1,361 kg of food a day. As a baleen whale, they have a series of 270-400 fringed overlapping baleen plates that hang from each side of their upper jaws where teeth might otherwise be located. These plates consist of a fingernail-like material called keratin that frays out into fine hairs on the ends. The plates are black and measure about 76 cm in length. During feeding, large volumes of water and food can be taken into their mouth because of the pleated grooves in their throat which allow for enormous expansion. As their mouth closes, water is expelled through their baleen plates, which trap the food which is then swallowed whole. This efficient system enables the largest animals on earth to feed on some of the smallest. They are also known to concentrate the food by forming a bubble curtain or bubble net, created by releasing air bubbles while swimming in circles beneath their prey.
Humpback whales mate during their winter migration to warmer waters, and eleven to twelve months later, upon their return to winter breeding grounds. They reach sexual maturity at 6-8 years of age or when males reach the length of 11.6 m and females are 12 m. Each female typically bears a calf every 2-3 years and the gestation period is 12 months. Humpback whale calves are between 3-4.5 m long at birth, and weigh up to 907 kg.
They nurse frequently on their mother's rich milk, which has a 45% to 60% fat content. Mothers must feed newborns about 45 kg of milk each day for a period of 5-7 months until they are weaned; calves may stay with mothers for up to a year. After weaning, calves have doubled their length and increased their weight by 5 times, attaining sizes of about 8.2 m and 9,072 kg. The maximum rate of reproduction for this species is one calf per year, but this is seldom practiced as it puts quite a strain on mother whales. Scientists estimate the average life span of humpbacks in the wild to be between 30-40 years, although no one knows for certain, yet.
Conservation Status & Comments
All rorquals have been hunted and some still are, although they are now protected by most nations subscribing to the International Whaling Commission. Their tendency to frequent coastal waters and their habitual return to the same regions each year made humpback whales vulnerable to exploitation by commercial whalers. Humpbacks were hunted for their oil, meat, and whalebone. Populations were drastically reduced in the early part of the 19th century, leaving only between 5-10% of the original populations remaining. In the North Pacific, it is estimated that as many as 15,000 humpbacks existed prior to 1900. That population was decimated to fewer than 1,000 individuals before an international ban on commercial whaling was instituted in 1964. Today, the North Pacific population which returns to Hawaii in the winter months to breed, now numbers approximately 6,000 - 8,000.
In spite of their recent strides toward recovery, humpbacks, Megaptera novaeangliae, are still designated as an endangered species in terms of two populations or subpopulations.
A taxon is Endangered when the best available evidence indicates that it meets any of the criteria A to E for Endangered (see Section V), and it is therefore considered to be facing a very high risk of extinction in the wild.
"Humpback whales are well-known to be susceptible to entanglement in fishing gear (Volgenau et al. 1995, Johnson et al. 2005). A total of nine humpback whale entanglements in fishing gear have been recorded off the coast of Oman. Eight of these animals were freed, another was observed swimming but trailing gear (Minton et al. in press). Analysis of scarring on the caudal peduncle region of photographically identified humpback whales in Oman indicates that between 30-40% are likely to have been involved in entanglements with fishing gear (Minton et al. in press). Fishing effort off the coast of Oman and in other parts of the Arabian Sea is increasing (Ministry of Agriculture and Fisheries 2002, Ministry of National Economy 2003, FAO 2007) and drifting and set gillnets as well as traps are already widely used (Stengel and Al Harthy 2002).
The Arabian Sea humpback whale population is small, and any human-induced mortality, especially of females, must be a concern.
Humpback whales have been legally protected from commercial whaling in the southern hemisphere since 1963, and the Arabian Sea region has always been a closed area to commercial whaling under the International Convention for the Regulation of Whaling. However, humpback whales were taken from the region illegally by Soviet pelagic operations in 1965 and 1966. The hunting of any cetacean species is prohibited by law in Oman. At the species level, the humpback whale is listed in Appendix I of both CITES and CMS. The Arabian Sea is also part of the International Whaling Commission's Indian Ocean Sanctuary.
The potential for successful conservation of humpback whales in the region is considered to be high, provided that range state governments are made aware of this population's precarious status. The countries of the Arabian region are generally affluent and in a good position to implement marine conservation measures for humpback whales in addition to those already initiated for other taxa, such as sea turtles. A coordinated series of marine protected areas, combined with species-specific protection measures, could greatly enhance the long-term prospects for humpback whales in the region."
"During the last two centuries, Humpback Whales have been hunted intensively, especially in the southern hemisphere, where it was estimated that populations were reduced to a few percent of their pre-exploitation abundance (Chapman 1974). Based on catch records corrected for illegal Soviet whaling, a total of more than 200,000 Humpback Whales were killed in the Southern Hemisphere from 1904 to 1980 (Clapham and Baker 2002). Catches during the 19th century in the South Pacific by American whalers were made mainly during winter months in three tropical breeding grounds: off Colombia and Ecuador, around the Tongan archipelago, and northwest of New Caledonia (Townsend 1935, Mackintosh 1942). During the 20th century, Humpback Whales were hunted along their migratory corridors, such as along the coasts of New Zealand and Australia, and more intensively in their feeding areas in sub-Antarctic and Antarctic waters (Mackintosh 1942, 1965). The IWC gave legal protection to Humpback Whales from commercial whaling in 1966 but they continued to be killed illegally by whalers from the Soviet Union until 1972. Illegal Soviet takes of 25,000 Humpback Whales in two seasons (1959/60 and 1960/61) precipitated a population crash and the closure of land stations in Australia and New Zealand (Mikhalev 2000, Clapham et al. 2005).
Japan proposed to kill 50 humpback whales as part of its program of scientific research under special permit (scientific whaling) in the IWC management areas IV and V in the Antarctic. Areas IV and V have demonstrated links with breeding stock E. Japan postponed its proposed catch in the 2007/08 season but have not removed Humpback Whales from its future whaling program. The continuation of this program has the potential to slow the recovery of the Oceania subpopulation.
Mortality of Humpback Whales due to entanglements in fishing gear and collisions with ships have been reported in the Southern Hemisphere (IWC 2001). Entanglement of Humpback Whales in pot lines occurs in both New Zealand and Australia. There is little information from around the rest of the South Pacific, but a humpback mother (with calf) was reported entangled in a longline in 2007 (N. Hauser, reported in SPWRC 2008) and another Humpback was struck and killed by a vessel in 1999 in Tonga (Diver 2004).
Although Humpback Whales have been legally protected from commercial whaling since 1966, they can still be killed for the purposes of scientific research under Article VIII of the International Convention for the Regulation of Whaling. The IWC's Southern Ocean Whale Sanctuary (e.g. the northern boundary of this Sanctuary follows the 40°S parallel of latitude except in the Indian Ocean sector where it joins the southern boundary of that sanctuary at 55°S, and around South America and into the South Pacific where the boundary is at 60°S) provides an additional layer of protection to Humpback Whales while on their summer feeding grounds in Antarctica, although whales inside the Sanctuary can still be killed under Article VIII.
At present, more than 12 million km2 of EEZs of more than a dozen South Pacific countries and territories have been designated as whale sanctuaries. This provides protection from commercial whaling for Humpback Whales in some of their breeding areas. Most recently an MoU under the CMS convention has been designed to protect cetaceans and their habitats in the South Pacific. It has already been signed by several countries and territories.
New Zealand and Australia have active disentanglement programs to release any Humpback Whales captured in fishing gear."
Only North Pacific right whales, another species of baleen whale, are considered more endangered than humpbacks in the North Pacific.
Visit the nonprofit group Whale Trust whose mission is to promote, support and conduct scientific research on humpback whales and the marine environment, and develop public education programs based directly on the results of scientific research.
References & Further Research
Minton, G., Collins, T., Pomilla, C., Findlay, K.P., Rosenbaum, H., Baldwin, R. & Brownell Jr., R.L. 2008. Megaptera novaeangliae (Arabian Sea subpopulation). In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1 www.iucnredlist.org.
Childerhouse, S., Jackson, J., Baker, C.S., Gales, N., Clapham, P.J. & Brownell Jr., R.L. 2008. Megaptera novaeangliae (Oceania subpopulation). In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1 www.iucnredlist.org.
Humpback Whale ACS Cetacean Fact Sheet
Nature Photography by Leo Kulinski, Jr.
Jefferson, T.A., S. Leatherwood, and M.A. Webber, FAO species identification guide, Marine mammals of the world, Rome, FAO. 1993. 320 p. 587 figs.
Rolf Hicker Nature Photography
U.S. Fish & Wildlife Service Endangered Species
Whale Trust: promotes, supports and conducts scientific research on Humpback whales
Whale and Dolphin Conservation Society (WDCS)
Research Megaptera novaeangliae » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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