| Right whales[1] | |
|---|---|
| A female North Atlantic Right Whale with her calf in the ocean. | |
| Size comparison against an average human | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Cetacea |
| Suborder: | Mysticeti |
| Family: | Balaenidae |
| Genus: | Eubalaena Gray, 1864 |
| Type species | |
| Balaena australis Desmoulins, 1822 |
|
| Species | |
| Range of the Eubalaena species. | |
| Synonyms | |
|
|
Right whales are three species of large baleen whales consisting of two genera in the family Balaenidae of order Cetacea. Their bodies are very dark gray or black and rotund.
They are called "right whales" because whalers thought the whales were the "right" ones to hunt, as they float when killed and often swim within sight of shore. They are also incredibly friendly, and often swam right up to boats as well. As such, they were hunted nearly to extinction during the active years of the whaling industry. Today, instead of hunting them, people often watch these acrobatic animals for pleasure. Genetic evidence appears to have settled a long-standing question about whether to include the largest, the Arctic-dwelling bowhead whale, with the rest. All four are included in the taxonomic family Balaenidae, and all four are generally referred to as right whales. This article focuses on the three species of the genus Eubalaena.
A fifth species of right whale was proposed by Emmanuel Swedenborg in the 18th century - the so called "Swedenborg whale". The description of this putative species was based on a collection of fossil bones unearthed at Norra Vanga, Sweden, in 1705 and believed to be those of giants. The bones were examined by Swedenborg who realised that they belong to a species of whale. The existence of this species has been and is currently debated. Evidence for a putative fifth species was discovered during the construction of a motorway in Strömstad, Sweden.[2]
Contents |
The bowhead whale is currently considered a separate species and was given its own genus 'Balaena' by Gray in 1821. The other three species occupy genus Eubalaena. Scientists see greater differences among the three Balaenoptera species than between them and the Bowhead Whale. A future review will likely place all four species in one genus.[3] Little genetic evidence supports the historic two-genera view.
Authorities have repeatedly recategorized the three populations of Eubalaena right whales, in one, two or three species. In the whaling era, there was thought to be a single species. Later, morphological factors such as differences in the skull shape of northern and southern animals indicated that there were at least two species—one in the northern hemisphere, the other in the Southern Ocean.[4] Right whales are not thought to cross equatorial waters to make contact with the other (sub)species or (inter)breed.[5]
Genetic evidence demonstrates that the northern and southern populations have not interbred for between 3 million and 12 million years, confirming that the southern right whale is a distinct species. More surprising was the discovery that the northern hemisphere Pacific and Atlantic populations are also distinct, and that the Pacific species (now known as the North Pacific right whale) is more closely related to the southern right whale than to the North Atlantic right whale. While Rice continued to list two species in his 1998 classification,[6] Rosenbaum et al. disagreed in 2000[7] and Brownell et al. in 2001.[8] In 2005, Mammal Species of the World listed three species, indicating a shift to this conclusion.[1]
Whale lice, parasitic cyamid crustaceans that live off skin debris, offer further information through their own genetics. Because these lice reproduce much more quickly than whales, their genetic diversity is greater. Marine biologists at the University of Utah examined these louse genes and determined that their hosts split into three species 5–6 million years ago, and that these species were all equally abundant before whaling began in the 11th century.[9] The communities first split because of the joining of North and South America. The heat of the equator then created a second split, into northern and southern groups. "This puts an end to the long debate about whether there are three [Eubalaena] species of right whale. They really are separate beyond a doubt", Jon Seger, the project's leader, told BBC News.[10]
A total of five Balaena fossils have been found in Europe and North America in deposits ranging from the late Miocene (about 10 mya) to early Pleistocene (about 1.5 mya). These five specimens each have their own species status—B. affinis, B. etrusca, B. montalionis, B. primigenius and B. prisca. The last of these may prove to be the modern bowhead. Prior to these there is a long gap before reaching the next related cetacean in the fossil record—Morenocetus was found in a South American deposit dating back 23 million years.
Due to their familiarity to whalers over a number of centuries the right whales have had many names. These names were used throughout the world, reflecting the fact that only one species was recognized at the time. In his novel Moby-Dick, Herman Melville writes:
Halibalaena (Gray, 1873) and Hunterius (Gray, 1866) are junior synonyms for the genus Eubalaena. E. australis is the type species.[1]
The species-level synonyms are:[1]
The pygmy right whale (Capera marginata), a much smaller whale of the southern hemisphere, was also included in the Balaenidae family, but has recently been found to warrant a separate family, Neobalaenidae.
Unlike other whales, right whales have distinctive callosities (roughened patches of skin) on their heads, along with a broad back without a dorsal fin, occasionally with white belly patches, and a long arching mouth that begins above the eye. The callosities appear white due to large colonies of cyamids (whale lice).[11][12] Right whales can grow up to 18 m (59 ft) long and weigh up to 100 short tons (91 t), significantly larger than humpbacks or grays, but smaller than blues.
An unusually large forty percent of body weight is blubber, which is of relatively low density. Consequently, unlike many other species of whale, dead right whales float.[13]
Adults may be between 11–18 m (36–59 ft) in length and typically weigh 60–80 short tons (54–73 t). The most typical lengths are 13–16 m (43–52 ft). The body is extremely thick with girth as much as 60% of total body length in some cases. The tail fluke is broad (up to 40% of body length). The North Pacific species is on average the largest of the three species. The largest specimens may weigh 100 short tons (91 t).
Right whales have a distinctive wide V-shaped blow, caused by the widely spaced blowholes on the top of the head. The blow rises 5 m (16 ft) above the surface.[14]
Right whales have between 200 and 300 baleen plates on each side of the mouth. These are narrow and approximately 2 m (6.6 ft) long, and are covered in very thin hairs. The plates enable the whale to filter feed.
The testicles appear to be the largest of any animal, each weighing around 500 kg (1,100 lb). The relative size is also large, at 1% of the whale's total body weight. This suggests that sperm competition is important in mating.[14]
The mean age of first parturition in North Atlantic right whales is estimated at between 7.5[15] to 9[16] years. Females breed every 3–4 years.[15][17] Both reproduction and calving take place during the winter months.[18] Calves are approximately 1 short ton (0.91 t) in weight and 4–6 m (13–20 ft) in length at birth following a gestation period of 1 year. The right whale grows rapidly in its first year, typically doubling in length. Weaning occurs after eight months to one year and the growth rate in later years is not well understood—it may be highly dependent on whether a calf stays with its mother for a second year.[3]
Very little is known about the life span of right whales because they are so scarce scientists cannot readily study them. One of the few well-documented cases is of a female North Atlantic right whale that was photographed with a baby in 1935, then photographed again in 1959, 1980, 1985, and 1992. Consistent callosity patterns ensured that it was the same animal. She was last photographed in 1995 with a seemingly fatal head wound, presumably from a ship strike. The animal died at at least 70 years of age. Research on the bowhead whale suggests this lifespan is not uncommon and may even be exceeded.[3][19]
Right whales swim slowly, reaching only 5 kn (9.3 km/h) at top speed, but are highly acrobatic and frequently breach (jump clear of the sea surface), tail-slap and lobtail. Like other baleen whales, the species is not gregarious and the typical group size is only two. Groups of up to twelve have been reported, but these were not close-knit and may have been transitory.
Right whales are often marked by large scaly gray-white patches on their skin, whose patterns are unique from animal to animal. These patches, called callosities, are colonies of crustaceans known as whale lice which can exist in the tens of thousands upon each whale. The parasitic creatures subsist on algae and dead skin, and while they are irritants, they do not cause significant harm to the whale.
The right whales' diet consists primarily of zooplankton, primarily the tiny crustaceans called copepods, as well as krill, and pteropods, although they are occasionally opportunistic feeders.
As with other baleens, they feed by filtering prey from the water. They swim with an open mouth, filling it with water and prey. The whale then expels the water, using its baleen plates to retain the prey. Prey must occur in sufficient numbers to trigger the whale's interest; be large enough that the baleen plates can filter it; and be slow enough that it cannot escape.[3] The "skimming" may take place on the surface, underwater, or even at the ocean's bottom, indicated by mud occasionally observed on right whales' bodies.[3]
The right whales' only predators are orcas and humans. When danger lurks, a group of right whales may form a circle, with their tails pointing outwards. This defense is not always successful and calves are occasionally lost.
The three Eubalaena species inhabit three distinct areas of the globe: the North Atlantic in the western Atlantic Ocean, the North Pacific in a band from Japan to Alaska and all areas of the Southern Ocean. The whales can only cope with the moderate temperatures found between 20 and 60 degrees in latitude. The warm equatorial waters form a barrier that prevents mixing between the northern and southern groups. Although the Southern species in particular must travel across open ocean to reach its feeding grounds, the species is not considered to be pelagic. In general, they prefer to stay close to peninsulas and bays and on continental shelves, as these areas offer greater shelter and an abundance of their preferred foods.
Because the oceans are so large, it is very difficult to accurately gauge whale population sizes. Approximate figures:
Almost all of the 400 North Atlantic right whales live in the western North Atlantic Ocean. In spring, summer and autumn, they feed in areas off the Canadian and north-east U.S. coasts in a range stretching from New York to Nova Scotia. Particularly popular feeding areas are the Bay of Fundy and Cape Cod Bay. In winter, they head south towards Georgia and Florida to give birth.
There have been a smattering of sightings further east over the past few decades; several sightings were made close to Iceland in 2003. It is possible that these are the remains of a virtually extinct eastern Atlantic stock, but examination of old whalers' records suggests that they are more likely to be strays.[3] However, a few sightings are regular between Norway, Ireland, Spain, Portugal, the Canary Islands and even Italy[20] and Sicily;[21] at least the Norway individuals come from the Western stock.[22]
The North Pacific right whale appears to occur in two populations. The population in the eastern North Pacific/Bering Sea is extremely low, numbering about 30 individuals.[23] A larger western population of 100-200 appears to be surviving in the Sea of Okhotsk, but very little is known about this population. Thus, the two northern right whale species are the most endangered of all large whales and two of the most endangered animals in the world. Based on current population density trends, both species are predicted to become extinct within 200 years.[24] The Pacific species was historically found in summer from the Sea of Okhotsk in the west to the Gulf of Alaska in the east, generally north of 50°N. Today, sightings are very rare and generally occur in the mouth of the Sea of Okhotsk and in the eastern Bering Sea. Although this species is very likely to be migratory like the other two species, its movement patterns are not known.
The estimate of 7,000 southern right whales came about following an IWC workshop held in Cape Town in March 1998. Researchers used data about adult female populations from three surveys (one in each of Argentina, South Africa and Australia collected during the 1990s) and extrapolated to include unsurveyed areas, number of males and calves using available male:female and adult:calf ratios to give an estimated 1999 figure of 7,000 animals.[25]
The southern right whale spends the summer months in the far Southern Ocean feeding, probably close to Antarctica. It migrates north in winter for breeding and can be seen around the coasts of Argentina, Australia, Brazil, Chile, Mozambique, New Zealand and South Africa.
Since hunting of the southern right whale ceased, stocks are estimated to have grown by 7% a year. It appears that the South American, South African and Australasian groups intermix very little, if at all, because of the strong fidelity of mothers to their feeding and calving grounds. The mother passes these instincts to her calves.[3]
In Brazil, more than 300 individuals have been cataloged through photo identification (using their distinctive head callosities) by the Brazilian Right Whale Project, maintained jointly by Petrobras (the Brazilian state-owned oil company) and the International Wildlife Coalition. The State of Santa Catarina hosts a concentration of breeding and calving right whales from June to November, and females from this population are also known to calve off Argentinian Patagonia.
Vocalizations made by right whales are not elaborate compared to those made by other whale species. The whales make groans, pops and belches that are typically at frequencies around 500 Hertz. The purpose of the sounds is not known but may be a form of communication between whales within the same group.
Northern right whales responded to sounds similar to police sirens—sounds of much higher frequency than their own. On hearing the sounds they moved rapidly to the surface. The research was of particular interest because northern rights ignore most sounds, including those of approaching boats. Researchers speculate that this information may be useful in attempts to reduce the number of ship-whale collisions or to encourage the whales to surface for ease of harvesting.[24][26]
Right whales were so named because early whalers considered them the "right" whale to hunt. In the early centuries of shore-based whaling prior to 1712, right whales were virtually the only catchable large whales, for three reasons:
Basque people were the first to commercially hunt right whales. They began as early as the 11th century in the Bay of Biscay. They initially sought oil, but as meat preservation technology improved the animal was also used for food. Basque whalers reached eastern Canada by 1530[3] and the shores of Todos os Santos Bay (in Bahia, Brazil) by 1602. The last Basque voyages were made prior to the Seven Year's War (1756–1763). All attempts to revive the trade post-war failed. Basque shore whaling continued sporadically into the 19th century.
"Yankee whalers" from the new American colonies replaced the Basques. Setting out from Nantucket, Massachusetts and Long Island, New York, they took up to 100 animals in good years. By 1750 the commercial hunt of the North Atlantic right whale was basically over. The Yankee whalers moved into the South Atlantic before the end of the 18th century. The southernmost Brazilian whaling station was established in 1796, in Imbituba. Over the next one hundred years, Yankee whaling spread into the Southern and Pacific Oceans, where the Americans were joined by fleets from several European nations. The beginning of the 20th century saw much greater industrialization of whaling, and the harvest grew rapidly. By 1937, there had been, according to whalers' records, 38,000 takes in the South Atlantic, 39,000 in the South Pacific, 1,300 in the Indian Ocean, and 15,000 in the north Pacific. The incompleteness of these records means that the actual take was somewhat higher.[28]
As it became clear that stocks were nearly depleted, the world banned right whaling in 1937. The ban was largely successful, although violations continued for several decades. Madeira took its last two right whales in 1968. Japan took 23 Pacific right whales in the 1940s and more under scientific permit in the 1960s. Illegal whaling continued off the coast of Brazil for many years and the Imbituba land station processed right whales until 1973. The Soviet Union illegally took at least 3,212 Southern right whales during the 1950s and '60s, although it reported taking only four.[29]
The southern right whale has made Hermanus, South Africa one of the world centers for whale watching. During the winter months (July–October), southern right whales come so close to the shoreline that visitors can watch whales from strategically placed hotels. The town employs a "whale crier" (cf. town crier) to walk through the town announcing where whales have been seen. Southern Right Whales can also be watched at other winter breeding grounds.
In Brazil, Imbituba in Santa Catarina has been recognized as the National Right Whale Capital and holds annual Right Whale Week celebrations in September, when mothers and calves are more often seen. The old whaling station there has been converted to a museum documenting the history of right whales in Brazil. In winter in Argentina, Península Valdés in Patagonia hosts the largest breeding population of the species, with more than 2,000 animals catalogued by the Whale Conservation Institute and Ocean Alliance.[30]
The leading cause of death among the North Atlantic right whale, which migrates through some of the world's busiest shipping lanes while journeying off the east coast of the United States and Canada, is from being struck by ships.[31] At least 16 ship strike deaths were reported between 1970 and 1999, and probably more remain unreported.[3] According to NOAA, 25 of the 71 right whale deaths reported since 1970 resulted from ship strikes.[32] Recognizing that this toll could tip the delicately balanced species towards extinction, in July 1997, the U.S. National Oceanic and Atmospheric Administration's (NOAA) introduced Atlantic Large Whale Take Reduction Plan.[33] A key part of the plan was the introduction of mandatory reporting of large whale sightings by ships using U.S. ports.
A second major cause of morbidity and mortality in the North Atlantic right whale is entanglement in fishing gear. Right whales ingest plankton with wide open mouths, risking entanglement in any rope or net fixed in the water column. Rope wraps around upper jaws, flippers and tails. Most manage to escape with minor scarring, but some are seriously and persistently entangled. If observers notice, they can be successfully disentangled, but others die over a period of months. Animal welfare and extinction concerns align in emphasizing the harm of such entanglements.
Both the North Atlantic and North Pacific species are listed as a "species threatened with extinction which [is] or may be affected by trade" (Appendix I) by CITES, and as Conservation Dependent by the IUCN Red List, and as endangered under the U.S. Endangered Species Act.
The U.S. and Brazil added new protections for right whales in the 00's to address the two primary hazards. While environmental campaigners were, as reported in 2001, pleased about the plan's positive effects, they attempted to force the U.S. government to do more.[34] In particular, they advocated 12 knots (22 km/h) speed limits for ships within 40 km (25 mi) of U.S. ports in times of high right whale presence. Citing concerns about excessive trade disruption, it did not comply. The Defenders of Wildlife, the Humane Society of the United States and the Ocean Conservancy sued the National Marine Fisheries Service (a NOAA sub-agency) in September 2005 for "failing to protect the critically endangered North Atlantic Right Whale, which the agency acknowledges is 'the rarest of all large whale species' and which federal agencies are required to protect by both the Marine Mammal Protection Act and the Endangered Species Act", demanding emergency protection measures.[35] According to NOAA researchers, about 83 percent of right whale sightings in the mid-Atlantic region occur within 20 nautical miles (37 km) of shore.
On February 6, 2006, NOAA proposed its Strategy to Reduce Ship Strikes to North Atlantic Right Whales.[36] The proposal, opposed by some shipping interests, limited ship speeds during calving season. The proposal was implemented in 2008. On December 8, 2008, NOAA issued a press release that included the following:[32]
The Stellwagen Bank area has implemented an autobuoy program to acoustically detect right whales in the Boston Approaches and notify mariners via the Right Whale Listening Network website.
The southern right whale, listed as "endangered" by CITES and "lower risk - conservation dependent" by the IUCN, is protected in the jurisdictional waters of all countries with known breeding populations (Argentina, Australia, Brazil, Chile, New Zealand, South Africa and Uruguay). In Brazil, a federal Environmental Protection Area encompassing some 1,560 km2 (600 sq mi) and 130 km (81 mi) of coastline in Santa Catarina State was established in 2000 to protect the species' main breeding grounds in Brazil and promote whale watching.[37]