Saturday, September 29, 2018

THE RABBITS

Rabbits are small mammals in the family Leporidae of the order Lagomorpha (along with the hare and the pika). Oryctolagus cuniculus includes the European rabbit species and its descendants, the world's 305 breeds[1] of domestic rabbit. Sylvilagus includes thirteen wild rabbit species, among them the seven types of cottontail. The European rabbit, which has been introduced on every continent except Antarctica, is familiar throughout the world as a wild prey animal and as a domesticated form of livestock and pet. With its widespread effect on ecologies and cultures, the rabbit (or bunny) is, in many areas of the world, a part of daily life—as food, clothing, and companion, and as a source of artistic inspiration.
 
 RabbitMilwaukee.jpg
 

Terminology

Male rabbits are called bucks; females are called does. An older term for an adult rabbit is coney, while rabbit once referred only to the young animals.[2] Another term for a young rabbit is bunny, though this term is often applied informally (especially by children) to rabbits generally, especially domestic ones. More recently, the term kit or kitten has been used to refer to a young rabbit. A young hare is called a leveret; this term is sometimes informally applied to a young rabbit as well.
A group of rabbits is known as a colony or nest (or, occasionally, a warren, though this more commonly refers to where the rabbits live).[3] A group of baby rabbits produced from a single mating is referred to as a litter,[4] and a group of domestic rabbits living together is sometimes called a herd.[5]

Taxonomy

Rabbits and hares were formerly classified in the order Rodentia (rodent) until 1912, when they were moved into a new order, Lagomorpha (which also includes pikas). Below are some of the genera and species of the rabbit.
  • Brachylagus Idahoensis
    Pygmy rabbit
  • Nesolagus netscheri
    Sumatran Striped Rabbit
    (Model)
  • Oryctolagus cuniculus
    European rabbit
    (Feral Tasmanian specimen)
  • Pentalagus furnessi
    Amami rabbit
    (Taxidermy specimen)
  • Romerolagus diazi
    Volcano rabbit
    (Taxidermy specimen)


  • Sylvilagus aquaticus
    Swamp rabbit
    (Juvenile)
  • Sylvilagus audubonii
    Desert cottontail
  • Sylvilagus bachmani
    Brush rabbit
  • Sylvilagus brasiliensis
    Tapeti
    (Taxidermy specimen)
  • Sylvilagus palustris
    hefneri
    Lower Keys
    marsh rabbit
Order Lagomorpha
    Family Leporidae

Hare
Johann Daniel Meyer (1748)
Rabbit
Johann Daniel Meyer (1748)

Differences from hares

Main article: Hare
Hares are precocial, born relatively mature and mobile with hair and good vision, while rabbits are altricial, born hairless and blind, and requiring closer care. Hares (and cottontail rabbits) live a relatively solitary life in a simple nest above the ground, while most rabbits live in social groups underground in burrows or warrens. Hares are generally larger than rabbits, with ears that are more elongated, and with hind legs that are larger and longer. Hares have not been domesticated, while descendants of the European rabbit are commonly bred as livestock and kept as pets.

Domestication

Main article: Domestic rabbit
Rabbits have long been domesticated. Beginning in the Middle Ages, the European rabbit has been widely kept as livestock, starting in ancient Rome. Selective breeding has generated a wide variety of rabbit breeds, many of which (since the early 19th century) are also kept as pets. Some strains of rabbit have been bred specifically as research subjects.
As livestock, rabbits are bred for their meat and fur. The earliest breeds were important sources of meat, and so became larger than wild rabbits, but domestic rabbits in modern times range in size from dwarf to giant. Rabbit fur, prized for its softness, can be found in a broad range of coat colors and patterns, as well as lengths. The Angora rabbit breed, for example, was developed for its long, silky fur, which is often hand-spun into yarn. Other domestic rabbit breeds have been developed primarily for the commercial fur trade, including the Rex, which has a short plush coat.

Biology

Evolution

Development of the rabbit heart
(wax models)
Because the rabbit's epiglottis is engaged over the soft palate except when swallowing, the rabbit is an obligate nasal breather. Rabbits have two sets of incisor teeth, one behind the other. This way they can be distinguished from rodents, with which they are often confused.[6] Carl Linnaeus originally grouped rabbits and rodents under the class Glires; later, they were separated as the scientific consensus is that many of their similarities were a result of convergent evolution. However, recent DNA analysis and the discovery of a common ancestor has supported the view that they do share a common lineage, and thus rabbits and rodents are now often referred to together as members of the superorder Glires.[7]

Morphology

Skeleton of the rabbit
Since speed and agility are a rabbit's main defenses against predators (including the swift fox), rabbits have large hind leg bones and well developed musculature. Though plantigrade at rest, rabbits are on their toes while running, assuming a more digitigrade form. Rabbits use their strong nails for digging and (along with their teeth) for defense.[citation needed] Each front foot has four toes plus a dewclaw. Each hind foot has four toes (but no dewclaw).[8]
Melanistic coloring
Oryctologus cuniculus
European rabbit (wild)
Most wild rabbits (especially compared to hares) have relatively full, egg-shaped bodies. The soft coat of the wild rabbit is agouti in coloration (or, rarely, melanistic), which aids in camouflage. The tail of the rabbit (with the exception of the cottontail species) is dark on top and white below. Cottontails have white on the top of their tails.[9]
As a result of the position of the eyes in its skull, the rabbit has a field of vision that encompasses nearly 360 degrees, with just a small blind spot at the bridge of the nose.[10]

Hind limb elements

This image comes from a specimen in the Pacific Lutheran University natural history collection. It displays all of the skeletal articulations of rabbit's hind limbs.
The anatomy of rabbits hind limbs are structurally similar to that of other land mammals and contribute to their specialized form of locomotion. The Bones of the hind limbs consist of long bones (the femur, tibia, fibula, and phalanges) as well as short bones (the tarsals). These bones are created through endochondral ossification during development.[11] Like most land mammals, the round head of the femur articulates with the acetabulum of the ox coxae. The femur articulates with the tibia, but not the fibula, which is fused to the tibia. The tibia and fibula articulate with the tarsals of the pes, commonly called the foot. The hind limbs of the rabbit are longer than the front limbs. This allows them to produce their hopping form of locomotion. Longer hind limbs are more capable of producing faster speeds. Hares, which have longer legs than cottontail rabbits, are able to move considerably faster.[12] Rabbits stay just on their toes when moving this is called Digitigrade locomotion. The hind feet have four long toes that allow for this and are webbed to prevent them from spreading when hopping.[13] Rabbits do not have paw pads on their feet like most other animals that use digitigrade locomotion. Instead, they have coarse compressed hair that offers protection.[14]

Musculature

The rabbits hind limb (lateral view) includes muscles involved in the quadriceps and hamstrings.
Rabbits have muscled hind legs that allow for maximum force, maneuverability, and acceleration that is divided into three main parts; foot, thigh, and leg. The hind limbs of a rabbit are an exaggerated feature, that are much longer than the forelimbs providing more force. Rabbits run on their toes to gain the optimal stride during locomotion. The force put out by the hind limbs is contributed to both the structural anatomy of the fusion tibia and fibula, and muscular features.[15] Bone formation and removal, from a cellular standpoint, is directly correlated to hind limb muscles. Action pressure from muscles creates force that is then distributed through the skeletal structures. Rabbits that generate less force, putting less stress on bones are more prone to osteoporosis due to bone rarefaction.[16] In rabbits, the more fibers in a muscle, the more resistant to fatigue. For example, hares have a greater resistant to fatigue than cottontails. The muscles of rabbit's hind limbs can be classified into four main categories: hamstrings, quadriceps, dorsiflexors, or plantar flexors. The quadricep muscles are in charge of force production when jumping. Complimenting these muscles are the hamstrings which aid in short bursts of action. These muscles play off of one another in the same way as the plantar flexors and doriflexors, contributing to the generation and actions associated with force.[17]

Ears

Within the order lagomorphs, the ears are utilized to detect and avoid predators. In the family leporidae, the ears are typically longer than they are wide. For example, in black tailed jack rabbits, their long ears cover a greater surface area relative to their body size that allow them to detect predators from far away. Contrasted to cotton tailed rabbits, their ears are smaller and shorter, requiring predators to be closer to detect them before fleeing. Evolution has favored rabbits to have shorter ears so the larger surface area does not cause them to lose heat in more temperate regions. The opposite can be seen in rabbits that live in hotter climates, mainly because they possess longer ears that have a larger surface area that help with dispersion of heat as well as the theory that sound does not travel well in more arid air, opposed to cooler air. Therefore, longer ears are meant to aid the organism in detecting prey sooner rather than later in warmer temperatures.[18] The rabbit is characterized by its shorter ears while hares are characterized by their longer ears.[19] Rabbits ears are an important structure to aid thermoregulation and detect predators due to how the outer, middle, and inner ear muscles coordinate with one another. The ear muscles also aid in maintaining balance and movement when fleeing predators.[20]
Anatomy of mammalian ear.
Outer ear
The Auricle (anatomy), also known as the pinna is a rabbit's outer ear.[21] The rabbit's body surface is mainly taken up by the pinnae. It is theorized that the ears aid in dispersion of heat at temperatures above 30°C with rabbits in warmer climates having longer pinnae due to this. Another theory is that the ears function as shock absorbers that could aid and stabilize rabbit's vision when fleeing predators, but this has typically only been seen in hares.[22] The rest of the outer ear has bent canals that lead to the eardrum or tympanic membrane.[23]
Middle ear
The middle ear is filled with three bones called ossicles and is separated by the outer eardrum in the back of the rabbit's skull.The three ossicles are called hammer, anvil, and stirrup and act to decrease sound before it hits the inner ear. In general, the ossicles act as a barrier to the inner ear for sound energy.[23]
Inner ear
Inner ear fluid called endolymph receives the sound energy. After receiving the energy, later within the inner ear there are two parts: the cochlea that utilizes sound waves from the ossicles and the vestibular apparatus that manages the rabbit's position in regards to movement. Within the cochlea there is a basilar membrane that contains sensory hair structures utilized to send nerve signals to the brain so it can recognize different sound frequencies. Within the vestibular apparatus the rabbit possesses three semicircular canals to help detect angular motion.[23]

Thermoregulation

Thermoregulation is the process that an organism utilizes to maintain an optimal body temperature even if there are severe external conditions.[24] This process is carried out by the pinnae which takes up most of the rabbit's body surface and contain a vascular network and arteriovenous shunts.[25] In a rabbit, the optimal body temperature is around 21℃.[26] If their body temperature exceeds or does not meet this optimal temperature, the rabbit must return to homeostasis. Homeostasis of body temperature is maintained by the use of their large, highly vascularized ears that are able to change the amount of blood flow that passes through the ears.
Rabbits use their large vascularized ears which aid in thermoregulation to keep their body temperature at an optimal level.
Constriction and dilation of blood vessels in the ears are used to control the core body temperature of a rabbit. If the core temperature exceeds its optimal temperature greatly, blood flow is constricted to limit the amount of blood going through the vessels. With this constriction, there is only a limited amount of blood that is passing through the ears where ambient heat would be able to heat the blood that is flowing through the ears and therefore, increasing the body temperature. Constriction is also used when the ambient temperature is much lower than that of the rabbit's core body temperature. When the ears are constricted it again limits blood flow through the ears to conserve the optimal body temperature of the rabbit. If the ambient temperature is either 15 degrees above or below the optimal body temperature, the blood vessels will dilate. With the blood vessels being enlarged, the blood is able to pass through the large surface area which causes it to either heat or cool down.
During the summer, the rabbit has the capability to stretch its pinnae which allows for greater surface area and increase heat dissipation. In the winter, the rabbit does the opposite and folds its ears in order to decrease its surface area to the ambient air which would decrease their body temperature.
The jackrabbit has the largest ears within the Oryctolagus cuniculus group. Their ears contribute to 17% of their total body surface area. Their large pinna were evolved to maintain homeostasis while in the extreme temperatures of the desert.

Digestion

Rabbits are herbivores that feed by grazing on grass, forbs, and leafy weeds. In consequence, their diet contains large amounts of cellulose, which is hard to digest. Rabbits solve this problem via a form of hindgut fermentation. They pass two distinct types of feces: hard droppings and soft black viscous pellets, the latter of which are known as caecotrophs and are immediately eaten (a behaviour known as coprophagy). Rabbits reingest their own droppings (rather than chewing the cud as do cows and numerous other herbivores) to digest their food further and extract sufficient nutrients.[27]
Rabbits graze heavily and rapidly for roughly the first half-hour of a grazing period (usually in the late afternoon), followed by about half an hour of more selective feeding.[citation needed] In this time, the rabbit will also excrete many hard fecal pellets, being waste pellets that will not be reingested.[citation needed] If the environment is relatively non-threatening, the rabbit will remain outdoors for many hours, grazing at intervals.[citation needed] While out of the burrow, the rabbit will occasionally reingest its soft, partially digested pellets; this is rarely observed, since the pellets are reingested as they are produced.[citation needed]
Video of a wild European rabbit
with ears twitching and a jump
Hard pellets are made up of hay-like fragments of plant cuticle and stalk, being the final waste product after redigestion of soft pellets. These are only released outside the burrow and are not reingested. Soft pellets are usually produced several hours after grazing, after the hard pellets have all been excreted.[citation needed] They are made up of micro-organisms and undigested plant cell walls.[citation needed]
Rabbits are hindgut digesters. This means that most of their digestion takes place in their large intestine and cecum. In rabbits, the cecum is about 10 times bigger than the stomach and it along with the large intestine makes up roughly 40% of the rabbit's digestive tract.[28] The unique musculature of the cecum allows the intestinal tract of the rabbit to separate fibrous material from more digestible material; the fibrous material is passed as feces, while the more nutritious material is encased in a mucous lining as a cecotrope. Cecotropes, sometimes called "night feces", are high in minerals, vitamins and proteins that are necessary to the rabbit's health. Rabbits eat these to meet their nutritional requirements; the mucous coating allows the nutrients to pass through the acidic stomach for digestion in the intestines. This process allows rabbits to extract the necessary nutrients from their food.[29]
The chewed plant material collects in the large cecum, a secondary chamber between the large and small intestine containing large quantities of symbiotic bacteria that help with the digestion of cellulose and also produce certain B vitamins. The pellets are about 56% bacteria by dry weight, largely accounting for the pellets being 24.4% protein on average. The soft feces form here and contain up to five times the vitamins of hard feces. After being excreted, they are eaten whole by the rabbit and redigested in a special part of the stomach. The pellets remain intact for up to six hours in the stomach; the bacteria within continue to digest the plant carbohydrates. This double-digestion process enables rabbits to use nutrients that they may have missed during the first passage through the gut, as well as the nutrients formed by the microbial activity and thus ensures that maximum nutrition is derived from the food they eat.[9] This process serves the same purpose in the rabbit as rumination does in cattle and sheep.[30]
Rabbits are incapable of vomiting.[31] Because rabbits can't vomit, if buildup occurs within the intestines (due often to a diet with insufficient fiber[32]), intestinal blockage can occur.[33]

Sleep

Further information: Sleep (non-human)
Rabbits may appear to be crepuscular, but their natural inclination is toward nocturnal activity.[34] In 2011, the average sleep time of a rabbit in captivity was calculated at 8.4 hours per day.[35] As with other prey animals, rabbits often sleep with their eyes open, so that sudden movements will awaken the rabbit to respond to potential danger.[36]

Diseases

For a more comprehensive list, see Category:Rabbit diseases.
In addition to being at risk of disease from common pathogens such as Bordetella bronchiseptica and Escherichia coli, rabbits can contract the virulent, species-specific viruses RHD ("rabbit hemorrhagic hisease", a form of calicivirus)[37] or myxomatosis. Among the parasites that infect rabbits are tapeworms (such as Taenia serialis), external parasites (including fleas and mites), coccidia species, and Toxoplasma gondii.[38][39] Domesticated rabbits with a diet lacking in high fiber sources, such as hay and grass, are susceptible to potentially lethal gastrointestinal stasis.[40] Rabbits and hares are almost never found to be infected with rabies and have not been known to transmit rabies to humans.[41]

Ecology

Rabbit kits
(one hour after birth)
Rabbits are prey animals and are therefore constantly aware of their surroundings. For instance, in Mediterranean Europe, rabbits are the main prey of red foxes, badgers, and Iberian lynxes.[42] If confronted by a potential threat, a rabbit may freeze and observe then warn others in the warren with powerful thumps on the ground. Rabbits have a remarkably wide field of vision, and a good deal of it is devoted to overhead scanning.[43] They survive predation by burrowing, hopping away in a zig-zag motion, and, if captured, delivering powerful kicks with their hind legs. Their strong teeth allow them to eat and to bite in order to escape a struggle.[44] The longest-lived rabbit on record, a domesticated European rabbit living in Tasmania, died at age 18.[45] The lifespan of wild rabbits is much shorter; the average longevity of an eastern cottontail, for instance, is less than one year.[46]
Rabbit burrow entrance
Rabbit burrow entrance

Habitat and range

Rabbit habitats include meadows, woods, forests, grasslands, deserts and wetlands.[47] Rabbits live in groups, and the best known species, the European rabbit, lives in underground burrows, or rabbit holes. A group of burrows is called a warren.[47]
More than half the world's rabbit population resides in North America.[47] They are also native to southwestern Europe, Southeast Asia, Sumatra, some islands of Japan, and in parts of Africa and South America. They are not naturally found in most of Eurasia, where a number of species of hares are present. Rabbits first entered South America relatively recently, as part of the Great American Interchange. Much of the continent has just one species of rabbit, the tapeti, while most of South America's southern cone is without rabbits.
The European rabbit has been introduced to many places around the world.[9]

Environmental problems

See also: Rabbits in Australia
Rabbits have been a source of environmental problems when introduced into the wild by humans. As a result of their appetites, and the rate at which they breed, feral rabbit depredation can be problematic for agriculture. Gassing, barriers (fences), shooting, snaring, and ferreting have been used to control rabbit populations, but the most effective measures are diseases such as myxomatosis (myxo or mixi, colloquially) and calicivirus. In Europe, where rabbits are farmed on a large scale, they are protected against myxomatosis and calicivirus with a genetically modified virus. The virus was developed in Spain, and is beneficial to rabbit farmers. If it were to make its way into wild populations in areas such as Australia, it could create a population boom, as those diseases are the most serious threats to rabbit survival. Rabbits in Australia and New Zealand are considered to be such a pest that land owners are legally obliged to control them.[48][49]

As food and clothing

Main article: Cuniculture
See also: Category:Rabbit dishes.
Saint Jerome in the Desert
[Note rabbit being chased by a (trained?) domesticated hound]
Taddeo Crivelli (Italian, died about 1479)
Rabbit being prepared in the kitchen
Simulation of daily life, mid-15th century
Hospices de Beaune, France
An Australian 'rabbiter' (c. 1900)
In some areas, wild rabbits and hares are hunted for their meat, a lean source of high quality protein.[50] In the wild, such hunting is accomplished with the aid of trained falcons, ferrets, or dogs, as well as with snares or other traps, and rifles. A caught rabbit may be dispatched with a sharp blow to the back of its head, a practice from which the term rabbit punch is derived.
Wild leporids comprise a small portion of global rabbit-meat consumption. Domesticated descendants of the European rabbit (Oryctolagus cuniculus) that are bred and kept as livestock (a practice called cuniculture) account for the estimated 200 million tons of rabbit meat produced annually.[51] In 1994, the countries with the highest consumption per capita of rabbit meat were Malta with 8.89 kilograms (19.6 lb), Italy with 5.71 kilograms (12.6 lb), and Cyprus with 4.37 kilograms (9.6 lb), falling to 0.03 kilograms (0.066 lb) in Japan. The figure for the United States was 0.14 kilograms (0.31 lb) per capita. The largest producers of rabbit meat in 1994 were China, Russia, Italy, France, and Spain.[52] Rabbit meat was once a common commodity in Sydney, Australia, but declined after the myxomatosis virus was intentionally introduced to control the exploding population of feral rabbits in the area.
In the United Kingdom, fresh rabbit is sold in butcher shops and markets, and some supermarkets sell frozen rabbit meat. At farmers markets there, including the famous Borough Market in London, rabbit carcasses are sometimes displayed hanging, unbutchered (in the traditional style), next to braces of pheasant or other small game. Rabbit meat is a feature of Moroccan cuisine, where it is cooked in a tajine with "raisins and grilled almonds added a few minutes before serving".[53] In China, rabbit meat is particularly popular in Sichuan cuisine, with its stewed rabbit, spicy diced rabbit, BBQ-style rabbit, and even spicy rabbit heads, which have been compared to spicy duck neck.[51] Rabbit meat is comparatively unpopular elsewhere in the Asia-Pacific.
An extremely rare infection associated with rabbits-as-food is tularemia (also known as rabbit fever), which may be contracted from an infected rabbit.[54] Hunters are at higher risk for tularemia because of the potential for inhaling the bacteria during the skinning process. An even more rare condition is protein poisoning, which was first noted as a consequence of eating rabbit meat to exclusion (hence the colloquial term, "rabbit starvation"). Protein poisoning, which is associated with extreme conditions of the total absence of dietary fat and protein, was noted by Vilhjalmur Stefansson in the late 19th century and in the journals of Charles Darwin.
In addition to their meat, rabbits are used for their wool, fur, and pelts, as well as their nitrogen-rich manure and their high-protein milk.[55] Production industries have developed domesticated rabbit breeds (such as the well-known Angora rabbit) to efficiently fill these needs.

In art, literature, and culture

Main article: Rabbits and hares in art
Rabbits are often used as a symbol of fertility or rebirth, and have long been associated with spring and Easter as the Easter Bunny. The species' role as a prey animal with few defenses evokes vulnerability and innocence, and in folklore and modern children's stories, rabbits often appear as sympathetic characters, able to connect easily with youth of all kinds (for example, the Velveteen Rabbit, or Thumper in Bambi).
Tile (19th c.) inspired by
Marvels of Creatures and
Strange Things Existing
(13th century Iranian book)
With its reputation as a prolific breeder, the rabbit juxtaposes sexuality with innocence, as in the Playboy Bunny. The rabbit (as a swift prey animal) is also known for its speed, agility, and endurance, symbolized (for example) by the marketing icon the "Energizer Bunny" (known in Europe and Australia as the "Duracell Bunny").

Folklore and mythology

Main article: List of fictional hares and rabbits
The rabbit often appears in folklore as the trickster archetype, as he uses his cunning to outwit his enemies.
"Rabbit fools Elephant
by showing the reflection of the moon."
Illustration (from 1354) of the Panchatantra
"Three rabbits" motif
Coat of arms of
Corbenay, France
The rabbit as trickster is a part of American popular culture, as Br'er Rabbit (from African-American folktales and, later, Disney animation) and Bugs Bunny (the cartoon character from Warner Bros.), for example.
Anthropomorphized rabbits have appeared in film and literature, in Alice's Adventures in Wonderland (the White Rabbit and the March Hare characters), in Watership Down (including the film and television adaptations), in Rabbit Hill (by Robert Lawson), and in the Peter Rabbit stories (by Beatrix Potter). In the 1920s, Oswald the Lucky Rabbit, was a popular cartoon character.
WWII USAF pilot D.R. Emerson
"flys with a rabbit's foot talisman,
a gift from a New York girl friend"

Superstition and urban legend

A rabbit's foot may be carried as an amulet, believed to bring protection and good luck. This belief is found in many parts of the world, with the earliest use being recorded in Europe c. 600 BC.[58]
On the Isle of Portland in Dorset, UK, the rabbit is said to be unlucky and even speaking the creature's name can cause upset among older island residents. This is thought to date back to early times in the local quarrying industry where (to save space) extracted stones that were not fit for sale were set side in what became tall, unstable walls. The local rabbits' tendency to burrow there would weaken the walls and their collapse resulted in injuries or even death. Thus, invoking the name of the culprit became an unlucky act to be avoided. In the local culture to this day, the rabbit (when he has to be referred to) may instead be called a “long ears” or “underground mutton”, so as not to risk bringing a downfall upon oneself. While it was true 50 years ago that a pub on the island could be emptied by calling out the word "rabbit", this has become more fable than fact in modern times.[citation needed]
In other parts of Britain and in North America, invoking the rabbit's name may instead bring good luck. "Rabbit rabbit rabbit" is one variant of an apotropaic or talismanic superstition that involves saying or repeating the word "rabbit" (or "rabbits" or "white rabbits" or some combination thereof) out loud upon waking on the first day of each month, because doing so will ensure good fortune for the duration of that month.
The "rabbit test" is a term, first used in 1949, for the Friedman test, an early diagnostic tool for detecting a pregnancy in humans. It is a common misconception (or perhaps an urban legend) that the test-rabbit would die if the woman was pregnant. This led to the phrase "the rabbit died" becoming a euphemism for a positive pregnancy test.
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Wednesday, September 26, 2018

THE SEI WHALE

The sei whale (/ˈseɪ/ or /ˈsaɪ/) (Balaenoptera borealis) is a baleen whale, the third-largest rorqual after the blue whale and the fin whale.[3] It inhabits most oceans and adjoining seas, and prefers deep offshore waters.[4] It avoids polar and tropical waters and semienclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical waters, with a lifespan of 70 years.[5]
Reaching 19.5 m (64 ft) long and weighing as much as 28 t (28 long tons; 31 short tons),[5] the sei whale consumes an average of 900 kg (2,000 lb) of food every day; its diet consists primarily of copepods, krill, and other zooplankton.[6] It is among the fastest of all cetaceans, and can reach speeds of up to 50 km/h (31 mph) (27 knots) over short distances.[6] The whale's name comes from the Norwegian word for pollock, a fish that appears off the coast of Norway at the same time of the year as the sei whale.[7]
Following large-scale commercial whaling during the late 19th and 20th centuries, when over 255,000 whales were killed,[8][9] the sei whale is now internationally protected,[2] although limited hunting occurs under a controversial research program conducted by Japan.[10] As of 2008, its worldwide population was about 80,000, less than a third of its prewhaling population.[11][12]
 
 Sei whale mother and calf Christin Khan NOAA.jpg
 Sei whale mother and calf

Etymology

Sei is the Norwegian word for pollock, also referred to as coalfish, a close relative of codfish. Sei whales appeared off the coast of Norway at the same time as the pollock, both coming to feed on the abundant plankton.[7] The specific name is the Latin word borealis, meaning northern. In the Pacific, the whale has been called the Japan finner; "finner" was a common term used to refer to rorquals. In Japanese, the whale was called iwashi kujira, or sardine whale, a name originally applied to Bryde's whales by early Japanese whalers. Later, as modern whaling shifted to Sanriku — where both species occur — it was confused for the sei whale. Now the term only applies to the latter species.[13][14] It has also been referred to as the lesser fin whale because it somewhat resembles the fin whale.[15] The American naturalist Roy Chapman Andrews compared the sei whale to the cheetah, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".[16]

Taxonomy


 Sei whale size.svg
 Size compared to an average human


On 21 February 1819, a 32-ft whale stranded near Grömitz, in Schleswig-Holstein. The Swedish-born German naturalist Karl Rudolphi initially identified it as Balaena rostrata (=Balaenoptera acutorostrata). In 1823, the French naturalist Georges Cuvier described and figured Rudolphi's specimen under the name "rorqual du Nord". In 1828, Rene Lesson translated this term into Balaenoptera borealis, basing his designation partly on Cuvier's description of Rudolphi's specimen and partly on a 54-ft female that had stranded on the coast of France the previous year (this was later identified as a juvenile fin whale, Balaenoptera physalus). In 1846, the English zoologist John Edward Gray, ignoring Lesson's designation, named Rudolphi's specimen Balaenoptera laticeps, which others followed.[17] In 1865, the British zoologist William Henry Flower named a 45-ft specimen that had been obtained from Pekalongan, on the north coast of Java, Sibbaldius (=Balaenoptera) schlegelii — in 1946 the Russian scientist A.G. Tomilin synonymized S. schlegelii and B. borealis, creating the subspecies B. b. schlegelii and B. b. borealis.[18][19] In 1884–85, the Norwegian scientist G. A. Guldberg first identified the "sejhval" of Finnmark with B. borealis.[20]
Sei whales are rorquals (family Balaenopteridae), baleen whales that include the humpback whale, the blue whale, Bryde's whale, the fin whale, and the minke whale. Rorquals take their name from the Norwegian word røyrkval, meaning "furrow whale",[21] because family members have a series of longitudinal pleats or grooves on the anterior half of their ventral surface. Balaenopterids diverged from the other families of suborder Mysticeti, also called the whalebone whales or great whales, as long ago as the middle Miocene.[22] Little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies have been identified—the northern sei whale (B. b. borealis) and southern sei whale (B. b. schlegelii).[23] Their ranges do not overlap.

Description

Painting of a sei whale.
The sei whale is the fourth-largest balaenopterid, after the blue whale (up to 180 tonnes, 200 tons) and the fin whale (up to 70 tonnes, 77 tons) and the humpback whale (up to 40 tonnes, 44.5 tons).[3] In the North Pacific, adult males average 13.7 m (45 ft) and adult females 15 m (49 ft), weighing 15 and 18.5 tonnes (16.5 and 20.5 tons),[24] while in the North Atlantic adult males average 14 m (46 ft) and adult females 14.5 m (48 ft), weighing 15.5 and 17 tonnes (17 and 18.5 tons)[24] In the Southern Hemisphere, they average 14.5 (47.5 ft) and 15 m (49 ft), respectively, weighing 17 and 18.5 tonnes (18.5 and 20.5 tons).[24] ([25] In the Northern Hemisphere, males reach up to 17.1 m (56 ft) and females up to 18.6 m (61 ft),[26] while in the Southern Hemisphere males reach 18.6 m (61 ft) and females 19.5 m (64 ft) — the authenticity of an alleged 22 m (72 ft) female caught 50 miles northwest of St. Kilda in July 1911 is doubted.[27][28][29] The largest specimens taken off Iceland were a 16.15 m (53.0 ft) female and a 14.6 m (48 ft) male, while the longest off Nova Scotia were two 15.8 m (52 ft) females and a 15.2 m (50 ft) male.[29][30] The longest measured during JARPN II cruises in the North Pacific were a 16.32 m (53.5 ft) female and a 15 m (49 ft) male.[31][32] The longest measured by Discovery Committee staff were an adult male of 16.15 m (53.0 ft) and an adult female of 17.1 m (56 ft), both caught off South Georgia.[33] Adults usually weigh between 15 and 20 metric tons — a 16.4 m (54 ft) pregnant female caught off Natal in 1966 weighed 37.75 tonnes (41.6 tons), not including 6% for loss of fluids during flensing.[24] Females are considerably larger than males.[5] At birth, a calf typically measures 4.4–4.5 m (14–15 ft) in length.

Anatomy

See also: Whale anatomy
A sei whale showing distinctive upright dorsal fin
The whale's body is typically a dark steel grey with irregular light grey to white markings on the ventral surface, or towards the front of the lower body. The whale has a relatively short series of 32–60 pleats or grooves along its ventral surface that extend halfway between the pectoral fins and umbilicus (in other species it usually extends to or past the umbilicus), restricting the expansion of the buccal cavity during feeding compared to other species.[34] The rostrum is pointed and the pectoral fins are relatively short, only 9%–10% of body length, and pointed at the tips.[7] It has a single ridge extending from the tip of the rostrum to the paired blowholes that are a distinctive characteristic of baleen whales.
The whale's skin is often marked by pits or wounds, which after healing become white scars. These are now known to be caused by "cookie-cutter" sharks (Isistius brasiliensis).[35] It has a tall, sickle-shaped dorsal fin that ranges in height from 38–90 cm (15–35 in) and averages 53–56 cm (21–22 in), about two-thirds of the way back from the tip of the rostrum.[36] Dorsal fin shape, pigmentation pattern, and scarring have been used to a limited extent in photo-identification studies.[37] The tail is thick and the fluke, or lobe, is relatively small in relation to the size of the whale's body.[7]
Photo displaying dozens of baleen plates: The plates face each other, and are evenly spaced at approximately 0.25 in (1 cm) intervals. The plates are attached to the jaw at the top, and have hairs at the bottom end.
Close-up view of baleen plates, used to strain food from the water
Adults have 300–380 ashy-black baleen plates on each side of the mouth, up to 80 cm (31 in) long. Each plate is made of fingernail-like keratin, which is bordered by a fringe of very fine, short, curly, wool-like white bristles.[6] The sei's very fine baleen bristles, about 0.1 mm (0.004 in) are the most reliable characteristic that distinguishes it from other rorquals.[38]
The sei whale looks similar to other large baleen whales. The best way to distinguish between it and Bryde's whale, apart from differences in baleen plates, is by the presence of lateral ridges on the dorsal surface of the Bryde's whale's rostrum. Large individuals can be confused with fin whales, unless the fin whale's asymmetrical head coloration is clearly seen. The fin whale's lower jaw's right side is white, and the left side is grey. When viewed from the side, the rostrum appears slightly arched (accentuated at the tip), while fin and Bryde's whales have relatively flat rostrums.[5]

Life history

Surface behaviors

Sei whales usually travel alone[39] or in pods of up to six individuals.[37] Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structure. During the southern Gulf of Maine influx in mid-1986, groups of at least three sei whales were observed "milling" on four occasions – i.e. moving in random directions, rolling, and remaining at the surface for over 10 minutes. One whale would always leave the group during or immediately after such socializing bouts.[37] The sei whale is among the fastest cetaceans. It can reach speeds of up to 50 km/h (27 kn) over short distances.[6] However, it is not a remarkable diver, reaching relatively shallow depths for 5 to 15 minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 60 seconds (range: 45–90 sec.). Unlike the fin whale, the sei whale tends not to rise high out of the water as it dives, usually just sinking below the surface. The blowholes and dorsal fin are often exposed above the water surface almost simultaneously. The whale almost never lifts its flukes above the surface, and are generally less active on water surfaces than closely related Bryde's whales; it rarely breaches.[5]

Feeding

Feeding at the surface
Photo of krill in water
Krill, shrimp-like marine invertebrate animals, are one of the sei whale's primary foods.
This rorqual is a filter feeder, using its baleen plates to obtain its food by opening its mouth, engulfing or skimming large amounts of the water containing the food, then straining the water out through the baleen, trapping any food items inside its mouth.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey to obtain its average of about 900 kg (2,000 lb) of food each day.[6] For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain, including zooplankton and small fish. The whale's diet preferences has been determined from stomach analyses, direct observation of feeding behavior,[40][41] and analyzing fecal matter collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species.[42] The whale competes for food against clupeid fish (herring and its relatives), basking sharks, and right whales.
In the North Atlantic, it feeds primarily on calanoid copepods, specifically Calanus finmarchicus, with a secondary preference for euphausiids, in particular Meganyctiphanes norvegica and Thysanoessa inermis.[43][44] In the North Pacific, it feeds on similar zooplankton, including the copepod species Neocalanus cristatus, N. plumchrus, and Calanus pacificus, and euphausiid species Euphausia pacifica, E. similis, Thysanoessa inermis, T. longipes, T. gregaria and T. spinifera. In addition, it eats larger organisms, such as the Japanese flying squid, Todarodes pacificus pacificus,[45] and small fish, including anchovies (Engraulis japonicus and E. mordax), sardines (Sardinops sagax), Pacific saury (Cololabis saira), mackerel (Scomber japonicus and S. australasicus), jack mackerel (Trachurus symmetricus) and juvenile rockfish (Sebastes jordani).[43][46] Some of these fish are commercially important. Off central California, they mainly feed on anchovies between June and August, and on krill (Euphausia pacifica) during September and October.[47] In the Southern Hemisphere, prey species include the copepods Neocalanus tonsus, Calanus simillimus, and Drepanopus pectinatus, as well as the euphausiids Euphausia superba and Euphausia vallentini[43] and the pelagic amphipod Themisto gaudichaudii.

Reproduction

See also: Whale reproduction
Mating occurs in temperate, subtropical seas during the winter. Gestation is estimated to vary around 10​3⁄4 months,[48] 11​1⁄4 months,[49] or one year,[50] depending which model of foetal growth is used. The different estimates result from scientists' inability to observe an entire pregnancy; most reproductive data for baleen whales were obtained from animals caught by commercial whalers, which offer only single snapshots of fetal growth. Researchers attempt to extrapolate conception dates by comparing fetus size and characteristics with newborns.
A newborn is weaned from its mother at 6–9 months of age, when it is 8–9 m (26–30 ft) long,[26] so weaning takes place at the summer or autumn feeding grounds. Females reproduce every 2–3 years,[48] usually to a single calf.[6] In the Northern Hemisphere, males are usually 12.8–12.9 m (42–42 ft) and females 13.3–13.5 m (44–44 ft) at sexual maturity, while in the Southern Hemisphere, males average 13.6 m (45 ft) and females 14 m (46 ft).[25] The average age of sexual maturity of both sexes is 8–10 years.[48] The whales can reach ages up to 65 years.[51]

Vocalizations

See also: Whale sound
The sei whale makes long, loud, low-frequency sounds. Relatively little is known about specific calls, but in 2003, observers noted sei whale calls in addition to sounds that could be described as "growls" or "whooshes" off the coast of the Antarctic Peninsula.[52] Many calls consisted of multiple parts at different frequencies. This combination distinguishes their calls from those of other whales. Most calls lasted about a half second, and occurred in the 240–625 hertz range, well within the range of human hearing. The maximum volume of the vocal sequences is reported as 156 decibels relative to 1 micropascal (μPa) at a reference distance of one metre.[52] An observer situated one metre from a vocalizing whale would perceive a volume roughly equivalent to the volume of a jackhammer operating two metres away.[53]
In November 2002, scientists recorded calls in the presence of sei whales off Maui. All the calls were downswept tonal calls, all but two ranging from a mean high frequency of 39.1 Hz down to 21 Hz of 1.3 second duration – the two higher frequency downswept calls ranged from an average of 100.3 Hz to 44.6 Hz over 1 second of duration. These calls closely resembled and coincided with a peak in "20- to 35-Hz irregular repetition interval" downswept pulses described from seafloor recordings off Oahu, which had previously been attributed to fin whales.[54] Between 2005 and 2007, low frequency downswept vocalizations were recorded in the Great South Channel, east of Cape Cod, Massachusetts, which were only significantly associated with the presence of sei whales. These calls averaged 82.3 Hz down to 34 Hz over about 1.4 seconds in duration. This call has also been reported from recordings in the Gulf of Maine, New England shelf waters, the mid-Atlantic Bight, and in Davis Strait. It likely functions as a contact call.[55]
BBC News quoted Roddy Morrison, a former whaler active in South Georgia, as saying, "When we killed the sei whales, they used to make a noise, like a crying noise. They seemed so friendly, and they'd come round and they'd make a noise, and when you hit them, they cried really. I didn't think it was really nice to do that. Everybody talked about it at the time I suppose, but it was money. At the end of the day that's what counted at the time. That's what we were there for."[56]

Range and migration

Drawing of a sei whale on a Faroese stamp, issued 17 September 2001
Sei whales live in all oceans, although rarely in polar or tropical waters.[5] The difficulty of distinguishing them at sea from their close relatives, Bryde's whales and in some cases from fin whales, creates confusion about their range and population, especially in warmer waters where Bryde's whales are most common.
In the North Atlantic, its range extends from southern Europe or northwestern Africa to Norway, and from the southern United States to Greenland.[4] The southernmost confirmed records are strandings along the northern Gulf of Mexico and in the Greater Antilles.[38] Throughout its range, the whale tends not to frequent semienclosed bodies of water, such as the Gulf of Mexico, the Gulf of Saint Lawrence, Hudson Bay, the North Sea, and the Mediterranean Sea.[5] It occurs predominantly in deep water, occurring most commonly over the continental slope,[57] in basins situated between banks,[58] or submarine canyon areas.[59]
In the North Pacific, it ranges from 20°N to 23°N latitude in the winter, and from 35°N to 50°N latitude in the summer.[60] Approximately 75% of the North Pacific population lives east of the International Date Line,[8] but there is little information regarding the North Pacific distribution. As of February 2017, the U.S. National Marine Fisheries Service estimated that the eastern North Pacific population stood at 374 whales.[61] Two whales tagged in deep waters off California were later recaptured off Washington and British Columbia, revealing a possible link between these areas,[62] but the lack of other tag recovery data makes these two cases inconclusive. Occurrences within the Gulf of California have been fewer.[63] In Sea of Japan and Sea of Okhotsk, whales are not common, although whales were more commonly seen than today in southern part of Sea of Japan from Korean Peninsula to the southern Primorsky Krai in the past, and there had been a sighting in Golden Horn Bay,[64] and whales were much more abundant in the triangle area around Kunashir Island in whaling days, making the area well known as sei – ground,[65] and there had been a sighting of a cow calf pair off the Sea of Japan coast of mid-Honshu during cetacean survey.
Sei whales have been recorded from northern Indian Ocean as well such as around Sri Lanka and Indian coasts.[66]
In the Southern Hemisphere, summer distribution based upon historic catch data is between 40°S and 50°S latitude in the South Atlantic and southern Indian Oceans and 45°S and 60°S in the South Pacific, while winter distribution is poorly known, with former winter whaling grounds being located off northeastern Brazil (7°S) and Peru (6°S).[2] The majority of the "sei" whales caught off Angola and Congo, as well as other nearby areas in equatorial West Africa, are thought to have been predominantly misidentified Bryde's whales. For example, Ruud (1952) found that 42 of the "sei whale" catch off Gabon in 1952 were actually Bryde's whales, based on examination of their baleen plates. The only confirmed historical record is the capture of a 14 m (46 ft) female, which was brought to the Cap Lopez whaling station in Gabon in September 1950. During cetacean sighting surveys off Angola between 2003 and 2006, only a single confirmed sighting of two individuals was made in August 2004, compared to 19 sightings of Bryde's whales.[67] Sei whales are commonly distributed along west to southern Latin America including along entire Chilean coasts, within Beagle Channel[68] to Isla Grande de Tierra del Fuego,[69] and possibly feed in the Aysen region.[70]

Migration

In general, the sei whale migrates annually from cool and subpolar waters in summer to temperate and subtropical waters for winter, where food is more abundant.[5] In the northwest Atlantic, sightings and catch records suggest the whales move north along the shelf edge to arrive in the areas of Georges Bank, Northeast Channel, and Browns Bank by mid- to late June. They are present off the south coast of Newfoundland in August and September, and a southbound migration begins moving west and south along the Nova Scotian shelf from mid-September to mid-November. Whales in the Labrador Sea as early as the first week of June may move farther northward to waters southwest of Greenland later in the summer.[71] In the northeast Atlantic, the sei whale winters as far south as West Africa such as off Bay of Arguin, off coastal Western Sahara and follows the continental slope northward in spring. Large females lead the northward migration and reach the Denmark Strait earlier and more reliably than other sexes and classes, arriving in mid-July and remaining through mid-September. In some years, males and younger females remain at lower latitudes during the summer.[29]
Despite knowing some general migration patterns, exact routes are incompletely known[29] and scientists cannot readily predict exactly where groups will appear from one year to the next.[72] F.O. Kapel noted a correlation between appearances west of Greenland and the incursion of relatively warm waters from the Irminger Current into that area.[73] Some evidence from tagging data indicates individuals return off the coast of Iceland on an annual basis.[74] An individual satellite-tagged off Faial, in the Azores, traveled more than 4,000 km (2,500 mi) to the Labrador Sea via the Charlie-Gibbs Fracture Zone (CGFZ) between April and June 2005. It appeared to "hitch a ride" on prevailing currents, with erratic movements indicative of feeding behavior in five areas, in particular the CGFZ, an area of known high sei whale abundance as well as high copepod concentrations.[75] Seven whales tagged off Faial and Pico from May to June in 2008 and 2009 made their way to the Labrador Sea, while an eighth individual tagged in September 2009 headed southeast – its signal was lost between Madeira and the Canary Islands.[76]

Whaling

Main articles: Whaling and History of whaling
The development of explosive harpoons and steam-powered whaling ships in the late nineteenth century brought previously unobtainable large whales within reach of commercial whalers. Initially their speed and elusiveness,[77] and later the comparatively small yield of oil and meat partially protected them. Once stocks of more profitable right whales, blue whales, fin whales, and humpback whales became depleted, sei whales were hunted in earnest, particularly from 1950 to 1980.[3]

North Atlantic

A sei whale (foreground) caught off Finnmark.
In the North Atlantic between 1885 and 1984, 14,295 sei whales were taken.[8] They were hunted in large numbers off the coasts of Norway and Scotland beginning in the late 19th and early 20th centuries,[72] and in 1885 alone, more than 700 were caught off Finnmark.[78] Their meat was a popular Norwegian food. The meat's value made the hunting of this difficult-to-catch species profitable in the early twentieth century.[79]
In Iceland, a total of 2,574 whales were taken from the Hvalfjörður whaling station between 1948 and 1985. Since the late 1960s to early 1970s, the sei whale has been second only to the fin whale as the preferred target of Icelandic whalers, with meat in greater demand than whale oil, the prior target.[77]
Small numbers were taken off the Iberian Peninsula, beginning in the 1920s by Spanish whalers,[80] off the Nova Scotian shelf in the late 1960s and early 1970s by Canadian whalers,[71] and off the coast of West Greenland from the 1920s to the 1950s by Norwegian and Danish whalers.[73]

North Pacific

A sei whale being harpooned off Japan.
In the North Pacific, the total reported catch by commercial whalers was 72,215 between 1910 and 1975;[8] the majority were taken after 1947.[81] Shore stations in Japan and Korea processed 300–600 each year between 1911 and 1955. In 1959, the Japanese catch peaked at 1,340. Heavy exploitation in the North Pacific began in the early 1960s, with catches averaging 3,643 per year from 1963 to 1974 (total 43,719; annual range 1,280–6,053).[82] In 1971, after a decade of high catches, it became scarce in Japanese waters, ending commercial whaling in 1975.[43][83]
Off the coast of North America, sei whales were hunted off British Columbia from the late 1950s to the mid-1960s, when the number of whales captured dropped to around 14 per year.[3] More than 2,000 were caught in British Columbian waters between 1962 and 1967.[84] Between 1957 and 1971, California shore stations processed 386 whales.[47] Commercial Sei whaling ended in the eastern North Pacific in 1971.

Southern Hemisphere

A total of 152,233 were taken in the Southern Hemisphere between 1910 and 1979.[8] Whaling in southern oceans originally targeted humpback whales. By 1913, this species became rare, and the catch of fin and blue whales began to increase. As these species likewise became scarce, sei whale catches increased rapidly in the late 1950s and early 1960s.[43] The catch peaked in 1964–65 at over 20,000 sei whales, but by 1976, this number had dropped to below 2,000 and commercial whaling for the species ended in 1977.[3]

Post-protection whaling

Since the moratorium on commercial whaling, some sei whales have been taken by Icelandic and Japanese whalers under the IWC's scientific research programme. Iceland carried out four years of scientific whaling between 1986 and 1989, killing up to 40 sei whales a year.[85] Japanese scientists catch about 50 sei whales each year for this purpose. The research is conducted by the Institute of Cetacean Research (ICR) in Tokyo, a privately funded, nonprofit institution. The main focus of the research is to examine what they eat and to assess the competition between whales and fisheries. Dr. Seiji Ohsumi, Director General of the ICR, said,
"It is estimated that whales consume 3 to 5 times the amount of marine resources as are caught for human consumption, so our whale research is providing valuable information required for improving the management of all our marine resources."[86]
He later added,
"Sei whales are the second-most abundant species of whale in the western North Pacific, with an estimated population of over 28,000 animals. [It is] clearly not endangered."[87]
Conservation groups, such as the World Wildlife Fund, dispute the value of this research, claiming that sei whales feed primarily on squid and plankton which are not hunted by humans, and only rarely on fish. They say that the program is
"nothing more than a plan designed to keep the whaling fleet in business, and the need to use whales as the scapegoat for overfishing by humans."[10]
At the 2001 meeting of the IWC Scientific Committee, 32 scientists submitted a document expressing their belief that the Japanese program lacked scientific rigor and would not meet minimum standards of academic review.[88]
In 2010, a Los Angeles restaurant confirmed to be serving sei whale meat was closed by its owners after prosecution by authorities for handling a protected species. [89]

Conservation status

World map showing that the U.S., China, India, Japan, Australia, Mexico, Russia, South Africa, and most European and Latin American states are members, among others.
Member states of the International Whaling Commission (in blue)
The sei whale did not have meaningful international protection until 1970, when the International Whaling Commission first set catch quotas for the North Pacific for individual species. Before quotas, there were no legal limits.[90] Complete protection from commercial whaling in the North Pacific came in 1976.
Quotas on sei whales in the North Atlantic began in 1977. Southern Hemisphere stocks were protected in 1979. Facing mounting evidence that several whale species were threatened with extinction, the IWC established a complete moratorium on commercial whaling beginning in 1986.[5]
In the late 1970s, some "pirate" whaling took place in the eastern North Atlantic.[91] There is no direct evidence of illegal whaling in the North Pacific, although the acknowledged misreporting of whaling data by the Soviet Union[92] means that catch data are not entirely reliable.
The species remained listed on the IUCN Red List of Threatened Species in 2000, categorized as "endangered".[2] Northern Hemisphere populations are listed as CITES Appendix II, indicating they are not immediately threatened with extinction, but may become so if they are not listed. Populations in the Southern Hemisphere are listed as CITES Appendix I, indicating they are threatened with extinction if trade is not halted.[6]
The sei whale is listed on both Appendix I[93] and Appendix II[93] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I[93] as this species has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them and also on Appendix II[93] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
Sei whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU) and the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ACCOBAMS).
The species is listed as endangered by the U.S. government National Marine Fisheries Service under the U.S. Endangered Species Act.[3]

Population estimates

The current population is estimated at 80,000, nearly a third of the prewhaling population.[7][11] A 1991 study in the North Atlantic estimated only 4,000.[94][95] Sei whales were said to have been scarce in the 1960s and early 1970s off northern Norway.[96] One possible explanation for this disappearance is that the whales were overexploited.[96] The drastic reduction in northeastern Atlantic copepod stocks during the late 1960s may be another culprit.[97] Surveys in the Denmark Strait found 1,290 whales in 1987, and 1,590 whales in 1989.[97] Nova Scotia's population estimates are between 1,393 and 2,248, with a minimum of 870.[71]
A 1977 study estimated Pacific Ocean totals of 9,110, based upon catch and CPUE data.[82] Japanese interests claim this figure is outdated, and in 2002 claimed the western North Pacific population was over 28,000,[87] a figure not accepted by the scientific community.[10] In western Canadian waters, researchers with Fisheries and Oceans Canada observed five Seis together in the summer of 2017, the first such sighting in over 50 years.[98] In California waters, there was only one confirmed and five possible sightings by 1991 to 1993 aerial and ship surveys,[99][100][100][101] and there were no confirmed sightings off Oregon coasts such as Maumee Bay and Washington. Prior to commercial whaling, the North Pacific hosted an estimated 42,000.[82] By the end of whaling, the population was down to between 7,260 and 12,620.[82]
In the Southern Hemisphere, population estimates range between 9,800 and 12,000, based upon catch history and CPUE.[94] The IWC estimated 9,718 whales based upon survey data between 1978 and 1988.[102] Prior to commercial whaling, there were an estimated 65,000.[94]

Mass deaths

Mass death events for sei whales have been recorded for many years and evidence suggests endemic poisoning ("marea roja") causes may have caused mass deaths in prehistoric times. In June 2015, scientists flying over southern Chile counted 337 dead sei whales, in what is regarded as the largest mass beaching ever documented.[103] The cause is not yet known; however, toxic algae blooms caused by unprecedented warming in the Pacific Ocean, known as the Blob, may be implicated.[104]


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 Sei whale range
 
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