Right whale
Right whales are three species of large baleen whales of the genus Eubalaena: the North Atlantic right whale, the North Pacific right whale and the southern right whale. They are classified in the family Balaenidae with the bowhead whale. Right whales have rotund bodies with arching rostrums, V-shaped blowholes and dark gray or black skin. The most distinguishing feature of a right whale is the rough patches of skin on its head, which appear white due to parasitism by whale lice. Right whales are typically long and weigh up to or more.
All three species are migratory, moving seasonally to feed or give birth. The warm equatorial waters form a barrier that isolates the northern and southern species from one another although the southern species, at least, has been known to cross the equator. In the Northern Hemisphere, right whales tend to avoid open waters and stay close to peninsulas and bays and on continental shelves, as these areas offer greater shelter and an abundance of their preferred foods. In the Southern Hemisphere, right whales feed far offshore in summer, but a large portion of the population occur in near-shore waters in winter. Right whales feed mainly on copepods but also consume krill and pteropods. They may forage the surface, underwater or even the ocean bottom. During courtship, males gather into large groups to compete for a single female, suggesting that sperm competition is an important factor in mating behavior. Gestation tends to last a year, and calves are weaned at eight months old.
Right whales were a preferred target for whalers because of their docile nature, their slow surface-skimming feeding behaviors, their tendency to stay close to the coast, and their high blubber content. Although the whales no longer face pressure from commercial whaling, humans remain by far the greatest threat to these species: the two leading causes of death are being struck by ships and entanglement in fishing gear. Today, the North Atlantic and North Pacific right whales are among the most endangered whales in the world.
Naming
A common explanation for the name right whales is that they were regarded as the ones to hunt, as they float when killed and often swim within sight of shore. They are quite docile and do not tend to shy away from approaching boats. As a result, they were hunted nearly to extinction during the active years of the whaling industry. However, this origin is questionable: in his history of American whaling, Eric Jay Dolin writes:For the scientific names, the generic name Eubalaena means "good or true whales", and specific names include glacialis for North Atlantic species, australis for Southern Hemisphere species, and japonica for North Pacific species.
Taxonomy
The right whales were first classified in the genus Balaena in 1758 by Carl Linnaeus, who at the time considered all of the right whales as a single species. Through the 19th and 20th centuries, in fact, the family Balaenidae has been the subject of great taxonometric debate. Authorities have repeatedly recategorized the three populations of right whale plus the bowhead whale, as one, two, three or four species, either in a single genus or in two separate genera. In the early whaling days, they were all thought to be a single species, Balaena mysticetus. Eventually, it was recognized that bowheads and right whales were in fact different, and John Edward Gray proposed the genus Eubalaena for the right whale in 1864. Later, morphological factors such as differences in the skull shape of northern and southern right whales indicated at least two species of right whale – one in the Northern Hemisphere, the other in the Southern Ocean.As recently as 1998, Rice, in his comprehensive and otherwise authoritative classification listed just two species: Balaena glacialis and Balaena mysticetus.
File:Southern right whale6.jpg|thumb|alt=Whale at surface|Southern right whale in the breeding grounds at Peninsula Valdés, Patagonia
In 2000, two studies of DNA samples from each of the whale populations concluded the northern and southern populations of right whale should be considered separate species. What some scientists found more surprising was the discovery that the North Pacific and North Atlantic populations are also distinct, and that the North Pacific species is more closely related to the southern right whale than to the North Atlantic right whale.
The authors of one of these studies concluded that these species have not interbred for between 3 million and 12 million years.
In 2001, Brownell et al. reevaluated the conservation status of the North Pacific right whale as a distinct species, and in 2002, the Scientific Committee of the International Whaling Commission accepted Rosenbaum's findings, and recommended that the Eubalaena nomenclature be retained for this genus.
A 2007 study by Churchill provided further evidence to conclude that the three different living right whale species constitute a distinct phylogenetic lineage from the bowhead, and properly belong to a separate genus.
The following cladogram of the family Balaenidae serves to illustrate the current scientific consensus as to the relationships between the three right whales and the bowhead whale.
A cladogram is a tool for visualizing and comparing the evolutionary relationships between taxa; the point where each node branches is analogous to an evolutionary branching – the diagram can be read left-to-right, much like a timeline.
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 their hosts split into three species 5–6 million years ago, and these species were all equally abundant before whaling began in the 11th century.
The communities first split because of the joining of North and South America. The rising temperatures of the equator then created a second split, into northern and southern groups, preventing them from interbreeding.
"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.
Others
The pygmy right whale, a much smaller whale of the Southern Hemisphere, was until recently considered a member of the Family Balaenidae. However, they are not right whales at all, and their taxonomy is presently in doubt. Most recent authors place this species into the monotypic Family Neobalaenidae,but a 2012 study suggests that it is instead the last living member of the Family Cetotheriidae, a family previously considered extinct.
Yet another species of right whale was proposed by Emanuel Swedenborg in the 18th century—the so-called Swedenborg whale. The description of this species was based on a collection of fossil bones unearthed at Norra Vånga, Sweden, in 1705 and believed to be those of giants. The bones were examined by Swedenborg, who realized they belong to a species of whale. The existence of this species has been debated, and further evidence for this species was discovered during the construction of a motorway in Strömstad, Sweden in 2009.
To date, however, scientific consensus still considers Hunterius swedenborgii to be a North Atlantic right whale.
According to a DNA analysis conducted, it was later confirmed that the fossil bones are actually from a bowhead whale.
Characteristics
Adult right whales are typically long. They have extremely thick bodies with a girth as much as 60% of total body length in some cases. They have large, broad and blunt pectoral flippers and the deeply notched, smoothly tipped tail flukes make up to 40% of their body length. The North Pacific species is on average the largest of the three species. weigh. The upper jaw of a right whale is a bit arched, and the lower lip is strongly curved. On each side of the upper jaw are 200–270 baleen plates. These are narrow and approximately long, and are covered in very thin hairs. Right whales have a distinctive wide V-shaped blow, caused by the widely spaced blowholes on the top of the head. The blow rises above the surface.The skin is generally black with occasional white blotches on the body, while some individuals have mottled patterns. Unlike other whales, a right whale has distinctive callosities on its head. The callosities appear white due to large colonies of cyamids.
Each individual has a unique callosities pattern. In 2016, a competitive effort resulted in the use of facial recognition software to derive a process to uniquely identify right whales with about 87% accuracy based on their callosities. The primary role of callosities has been considered to be protection against predators. Right whale declines might have also reduced barnacles.
An unusually large 40% of their body weight is blubber, which is of relatively low density. Consequently, unlike many other species of whale, dead right whales tend to float. Many southern right whales are seen with rolls of fats behind blowholes that northern species often lack, and these are regarded as a sign of better health condition due to sufficient nutrition supply, and could have contributed in vast differences in recovery status between right whales in the southern and northern hemisphere, other than direct impacts by humankind.
The penis on a right whale can be up to – the testes, at up to in length, in diameter, and weighing up to 525 kg, are also by far the largest of any animal on Earth. The blue whale may be the largest animal on the planet, yet the testicles of the right whale are ten times the size of those of the blue whale. They also exceed predictions in terms of relative size, being six times larger than would be expected on the basis of body mass. Together, the testicles make up nearly 1% of the right whale's total body weight. This strongly suggests sperm competition is important in mating, which correlates to the fact that right whales are highly promiscuous.