Weddell seal

The Weddell seal (Leptonychotes weddellii) is a relatively large and abundant true seal (family: Phocidae) with a circumpolar distribution surrounding Antarctica. Weddell seals have the most southerly distribution of any mammal, with a habitat that extends as far south as McMurdo Sound (at 77°S). It is the only species in the genus Leptonychotes,[1] and the only member of the Antarctic tribe of lobodontine seals to prefer in-shore habitats on shore-fast ice over free-floating pack ice. Genetic evidence suggests that Weddell seal population numbers may have increased during the Pleistocene.[3] Because of its abundance, relative accessibility, and ease of approach by humans, it is the best-studied of the Antarctic seals. An estimated 800,000 individuals remain today. A genetic survey did not detect evidence of a recent, sustained genetic bottleneck in this species,[4] which suggests that populations do not appear to have suffered a substantial and sustained decline in the recent past. Weddell seal pups leave their mothers at a few months of age. In those months, they are fed by their mothers' warming and fat-rich milk. They leave when they are ready to hunt and are fat enough to survive in the harsh weather.

The Weddell seal was discovered and named in the 1820s during expeditions led by James Weddell, the British sealing captain, to the parts of the Southern Ocean now known as the Weddell Sea.[5] However, it is found in relatively uniform densities around the entire Antarctic continent.

Weddell seal[1]
Mikkelsen Harbour-2016-Trinity Island (D'Hainaut Island)–Weddell seal (Leptonychotes weddellii) 03
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Phocidae
Genus: Leptonychotes
Gill, 1872
L. weddellii
Binomial name
Leptonychotes weddellii
(Lesson, 1826)
WeddellRange 1
Weddell seal range
Weddell Seal (js)1
Weddell seal, Neko Harbour, Antarctica
Antarctic,Weddell seal-puppy (js) 44
Weddell seal pup with its grey natal coat, Deception Island
Weddell seal
Weddell seal
Bébé Phoque de Weddell - Baby Weddell Seal
Baby Weddell seal

Taxonomy and evolution

The Weddell seal shares a common recent ancestor with the other Antarctic seals, which are together known as the lobodontine seals. These include the crabeater seal (Lobodon carcinophaga), the Ross seal (Ommatophoca rossii), and the leopard seal (Hydrurga leptonyx).[6] These species share teeth adaptations including lobes and cusps useful for straining smaller prey items out of the water. The ancestral Lobodontini likely diverged from its sister clade, the Mirounga (elephant seals) in the late Miocene to early Pliocene, when they migrated southward and diversified rapidly to form four distinct genera in relative isolation around Antarctica.[6]

Physical traits

Weddell seals measure about 2.5–3.5 m (8 ft 2 in–11 ft 6 in) long and weigh 400–600 kg (880–1,320 lb).[7][8] Males weigh less than females, usually about 500 kg (1,100 lb) or less. Male and female Weddell seals are generally about the same length, though females can be slightly larger.[9] However, the male seal tends to have a thicker neck and a broader head and muzzle than the female.[10] A molecular genetic based technique has been established to confirm the sex of individuals in the laboratory.[11] The Weddell seal face has been compared to that of a cat due to a short mouth line and similarities in the structure of the nose and whiskers.[10] Their upturned mouths give them the appearance of smiling.

The Weddell seal grows a thin fur coat around its whole body except for small areas around the flippers. The colour and pattern of the coat varies, often fading to a duller colour as the seal ages.[9] This coat moults around the beginning of summer.[10] Adults are generally brown, with lighter ventral (belly) pelage. They are mottled with large darker and lighter patches, those on the belly being silvery white. Adult males usually bear scars, most of them around the genital region.

Young Weddell seals have gray pelage for the first 3–4 weeks; later, they turn a darker color. The pups reach maturity at three years of age. The pups are around half the length of their mother at birth, and weigh 25–30 kg (55–66 lb). They gain around 2 kg (4.4 lb) a day, and by 6–7 weeks old they can weigh around 100 kg (220 lb).[9]


Weddell seals are commonly found on fast ice, or ice fastened to land, and gather in small groups around cracks and holes within the ice.[12] In the winter, they stay in the water to avoid blizzards, with only their heads poking through breathing holes in the ice.[9] These seals are often observed lying on their sides when on land.[13] They are very docile, placid animals that can be easily approached.[10]

Weddell seals are non-migratory phocids that move regionally to follow the distribution of breathing holes in the ice between seasons.[14] Weddell seals dive to forage for food, maintain breathing holes in fast ice, and explore to find more ice holes.[15] These seals exhibit a diurnal haul-out pattern.[16] A higher frequency of seals haul out during the afternoon, usually around 4:00 PM, because of warmer air temperatures.[16]


Weddell seals return to fast ice colonies during the spring for birthing and breeding.[17] Weddell seal populations will often return to the same breeding sites over consecutive breeding seasons.[18] Depending on the latitude it inhabits, this marine mammal gives birth from early September through November, with those living at lower latitudes giving birth earlier.[14] Weddell seals usually give birth to one pup per year,[14] however the Weddell seal is one of the only species of seals that can give birth to twin pups.[5] Birth of the pup only takes around one to four minutes. Newborn pups weigh about 29 kg and grow to two times their weight within their first week of life.[14] The pups take their first swim around one to two weeks old.[14] During the first two weeks mother Weddell seals distinguish their pups through olfactory smells, specialized vocalizations, and stay in the same spatial area.[19] They can hold their breath for five minutes, enabling them to dive to depths of 100 m (330 ft).[14] After six to seven weeks, they are weaned and begin to hunt independently.[9] The average lifespan of a Weddell seal is about 30 years.[20]

Weddell seals have a high potential for polygyny. Males do not participate in raising newborn pups and instead focus on mating as much as possible during the breeding season. Additionally, fast ice breeding grounds causes females to cluster in large aggregations, making it easier for males to take control over his own harem.[18]

The mating season occurs during austral spring between late November and December after pups are weaned and females begin ovulating.[14] During the mating season, Weddell seals make noises loud enough to be felt through the ice.[5] Males defend underwater territories during the breeding season and have been observed to fight.[21] Copulation has only been observed to occur under water, where the female submits to the male as he approaches her dorsal side. The female is often bitten on the neck by her partner if she tries to escape or terminate copulation.[22] The seals are normally around six to eight years old when they first breed, but this can be much earlier for some females.[10]

Weddell seals undergo delayed implantation. The embryo is not embedded into the uterus until the beginning of austral summer, between mid-January and mid-February, allowing for birth under more favorable environmental conditions.[14]


Diving weddell seals
Diving Weddell seals

Weddell seals have been observed to dive as deep as 600 m for up to an hour[14] Such deep dives involve foraging sessions, as well as searching for cracks in the ice sheets that can lead to new breathing holes.[15] Weddell seals exhibit a diel dive pattern, diving deeper and longer during the day than at night.[23] After dropping away from a breathing hole in the ice, the seals become negatively buoyant in the first 30 to 50 m, allowing them to dive with little effort as they make a “meandering descent".[24] The seals can remain submerged for such long periods of time because of high concentrations of myoglobin in their muscles.[25]

Weddell seals' metabolism is relatively constant during deep-water dives, so another way to compensate for functioning with a lack of oxygen over an extended period of time must exist. Seals, unlike other terrestrial mammals such as humans, can undergo anaerobic metabolism for these extended dives, which causes a build-up of lactic acid in the muscles.[26] The seals can also release oxygenated blood from their spleens into the rest of their bodies, acting as an oxygen reserve.[27]


Male and female Weddell seals communicate through a variety of sounds, males specifically use “trills” to communicate sometimes. Weddell seals are also able to communicate to each other through different mediums. Weddell seals on ice are able to hear the calls of Weddell seals in the water as long as noise level on land is low and they are in close proximity of one another. Sound waves can be transmitted either through the ice itself or from water to breathing holes where female Weddell seals usually are when breeding.[28]

There have been recordings of Weddell seal vocalizations that are described as songs. Their songs consist of repetitive sequences of the same vocal elements, and they only vary slightly over time. Individual Weddell seals can each produce their own unique song, but singing behavior is not common when observing them.[29]

Vocalizations are also important in mother-pup Weddell seal interactions. Mother Weddell seals use vocalizations to call their pups from further distances when smell can no longer be used efficiently.[19] Pups also use higher, more urgent vocalizations when hungry to alert their mothers to feed.[30]

Diet and predation

Video of a Weddell seal in Antarctica
Video of a Weddell seal in Antarctica

Weddell seals are top predators in the Antarctic. They eat an array of fish, bottom-feeding prawns, cephalopods and crustaceans.[31] A sedentary adult eats around 10 kg (22 lb) a day, while an active adult eats over 50 kg (110 lb) a day.[9] Cod icefish constitute the majority of their diet. Cephalopods are common prey, and crustacean remains are sometimes found in Weddell seal scat, but at much lower rates than other prey species. They are opportunistic feeders that hunt in different parts of the water column depending on prey availability. Weddell seals hunt in both pelagic and benthic-demersal habitats.[32]

Although seabirds are not part of their diet, there have been sightings of them chasing and killing penguins in the wild. Other Antarctic phocids are known to be seabird predators, resulting in implications that penguin hunting is a learned behavior. There are recordings of four different penguin species being attacked by Weddell seals: Gentoo penguins, an emperor penguin, an Adélie penguin, and a chinstrap penguin. It has not been confirmed, however, if the penguins were consumed after being killed.[33]

Scientists believe Weddell seals rely mainly on eyesight to hunt for food when there is light. However, during the Antarctic winter darkness, when there is no light under the ice where the seals forage, they rely on other senses, primarily the sense of touch from their vibrissae or whiskers, which are not just hairs, but very complicated sense organs with more than 500 nerve endings that attach to the animal’s snout. The hairs allow the seals to detect the wake of swimming fish and use that to capture prey.[24]

Weddell seals have no natural predators when on fast ice. At sea or on pack ice, they are prey for killer whales and leopard seals, which prey primarily on juveniles and pups.[9]


Weddell seals are circumpolar and widely distributed throughout the Southern Hemisphere where individuals inhabit areas of both pack ice and fast ice. Large numbers of individuals can be found most abundantly on fast ice that continues on until the Antarctic shoreline, and occasionally in pack ice regions located offshore—near the limits of the Antarctic Convergence.[34] A small population has also been observed year-round in Larsen Harbor, South Georgia.[35] Individuals have been reported wandering north of Antarctica in South America, New Zealand and south of Australia.[34]

Physical factors, such as glacial movement and tidal action, also increase fluctuations in distributions. For example, pupping colonies are highly variable due to these factors as they provide necessary areas for breathing.[14] Weddell seals are not migratory but move as the distribution of breathing holes and exit cracks within the ice change throughout the winter.  [14]


Throughout the early periods of the Antarctic exploration, Weddell seals suffered dramatic declines as they were hunted for food and oil. Fortunately, populations have since recovered after the elimination of commercial sealing in the 1950s.[34]

The effects of global climate change on Antarctic seals are still to be fully determined however, research estimates seal populations may decline as the availability of their habitat is extremely temperature sensitive thus making them potentially vulnerable.[36]

There are no immediate threats to the Weddell seal, and the species is not listed as endangered or threatened.[34] The Weddell seal is protected by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals.


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External links

Castellini Bluff

Castellini Bluff (78°09′00″S 167°10′00″E) is a rock bluff rising to c. 500 m between Dibble Bluff and Mount Nesos in west White Island, Ross Archipelago. Named by the Advisory Committee on Antarctic Names in 2005 after Michael A. Castellini, Institute of Marine Sciences, University of Alaska, Fairbanks, who studied the Weddell seal in McMurdo Sound sea ice areas from 1977 to 2004, including winter season research at White Island with Randall William Davis in 1981.

Circumpolar distribution

A circumpolar distribution is any range of a taxon that occurs over a wide range of longitudes but only at high latitudes; such a range therefore extends all the way around either the North Pole or the South Pole. Taxa that are also found in isolated high-mountain environments further from the poles are said to have arctic–alpine distributions.Animals with circumpolar distributions include the reindeer, polar bear, Arctic fox, snowy owl, snow bunting, king eider, brent goose and long-tailed skua in the north, and the Weddell seal and Adélie penguin in the south.

Plants with northern circumpolar distributions include Eutrema edwardsii (syn. Draba laevigata), Saxifraga oppositifolia, Persicaria vivipara and Honckenya peploides.

Davis Bluff

Davis Bluff (78°09′00″S 167°35′00″E) is a rock bluff that rises to 400 m in height. It is located 2 nautical miles (3.7 km) northeast of Isolation Point in east White Island, Ross Archipelago. Davis Bluff was named by the United States Board of Geographic names following the recommendation of its Advisory Committee on Antarctic Names in 2005 after Randall William Davis, Department of Marine Biology, Texas A&M University, Galveston, Texas. Dr. Davis studied the Weddell seal in McMurdo Sound sea ice areas from 1977 to 2003, including winter season research at White Island with his wife Ana Maria Davis, Michael A. Castellini and Markus Horning.

Earless seal

The earless seals, phocids or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.

East Antarctica

East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying on the Indian Ocean side of the continent, separated from West Antarctica by the Transantarctic Mountains. It lies almost entirely within the Eastern Hemisphere and its name has been accepted for more than a century. It is generally higher than West Antarctica and includes the Gamburtsev Mountain Range in the centre.

Apart from small areas of the coast, East Antarctica is permanently covered by ice. The only terrestrial plant life is lichens, mosses and algae clinging to rocks, and there are a limited range of invertebrates including nematodes, springtails, mites and midges. The coasts are the breeding ground for various seabirds and penguins, and the leopard seal, Weddell seal, elephant seal, crabeater seal and Ross seal breed on the surrounding pack ice in summer.


Echinophthiriidae is a family of lice in the suborder Anoplura, the sucking lice. This family of lice are parasites of seals and the river otter, and are the only insects that infest aquatic hosts.

These lice have adaptations influenced by the anatomy of their hosts. Because some marine mammals, such as fur seals, have a layer of air trapped under their waterproof coats that insulates them against cold water, their lice actually live in a mostly dry, warm habitat. Other mammals have blubber for insulation, so their skin is in contact with the water; their lice parasites live in a cold aquatic environment.Lice in this family have a chaetotaxy characterized by three kinds of setae: spines, scales, and hairs. Different species have different arrangements of these setae. Species also have various egg-laying habits, with some laying them singly or in clusters, and some cementing them to the hairs of the host animal. These lice have antennae but no eyes. In most species the middle and rear pairs of legs are larger with blunt claws while the front pair of legs is smaller with pointed claws. Scanning electron microscope examination shows that the species Antarctophthirus microchir uses its larger middle and rear pairs of legs to cling to the hairs of its host, and the smaller, pointed front legs are probably sensory structures.Depending on species and temperature, the life cycle of one of these lice can take about 2 to 4 weeks. Each species tends to favor a different part of the host animal's body; for example, Antarctophthirus ogmirhini lives on the back flippers and tail and Lepidophthirus macrorhini favors the flippers, including the digits and the webbing between them. Proechinophthirus fluctus lives under the fur, while Antarctophthirus callorhini prefers parts with naked skin, such as the nostrils and eyelids of the host. Lice may serve as intermediate hosts or vectors for parasites of their hosts. Echinophthirius horridus is an intermediate host of Dipetalonema spirocauda, a nematode parasite of harbour seals.There are 13 species classified in 5 genera. Taxa and their host animals include:

Genus Antarctophthirus

Antarctophthirus callorhini (on fur seals)

Antarctophthirus carlinii (on the Weddell seal)

Antarctophthirus lobodontis (on earless seals)

Antarctophthirus mawsoni (on earless seals)

Antarctophthirus microchir (on sea lions)

Antarctophthirus ogmirhini (on earless seals)

Antarctophthirus trichechi (on walruses)

Genus Echinophthirius, one species:

Echinophthirius horridus (on earless seals)

Genus Latagophthirus, one species:

Latagophthirus rauschi (on the river otter)

Genus Lepidophthirus, two species on the river otter:

Lepidophthirus macrorhini

Lepidophthirus piriformis

Genus Proechinophthirus, two species on fur seals and sea lions:

Proechinophthirus fluctus

Proechinophthirus zumpti


Hauling-out is a behaviour associated with pinnipeds (true seals, sea lions, fur seals and walruses) temporarily leaving the water. Hauling-out typically occurs between periods of foraging activity. Rather than remain in the water, pinnipeds haul-out onto land or sea-ice for reasons such as reproduction and rest. Hauling-out is necessary in seals for mating (with the exception of the Baikal seal) and giving birth (although a distinction is generally made between reproductive aggregations, termed "rookeries", and non-reproductive aggregations, termed "haul-outs"). Other benefits of hauling-out may include predator avoidance, thermoregulation, social activity, parasite reduction and rest.There is much variation in haul-out patterns among different seal species. Haul-out sites may be segregated by age and sex within the same species. Many species of pinniped have only a few localized rookeries where they breed, but periodically occupy hundreds of haul-out sites throughout the range. For example, the Australian fur seals breed on only nine islands in Bass Strait but also occupy up to 50 haul-out sites in south-east Australian waters, and Steller sea lions have around 50 rookeries throughout their range, but several hundred haul-out sites.

Hauling-out behaviour provides numerous benefits to pinnipeds besides reproduction. This behaviour has been shown to be used for activities such as thermoregulation, predator avoidance, moulting, nursing, and resting. Haul-out frequency, duration, and site location (ie. sea-ice, floating-ice, and terrestrial) are all influenced by physical constraints (ie. air temperature, wind speed, and time of day) and biological constraints (ie. moulting, age, and sex). Variations in hauling-out behaviour exist among pinnipeds for reasons such as geographical location.

Ice seal

Ice seal, or (in the Southern Hemisphere) pack-ice seal is a general term applied to any one of a number of pinniped species of the family Phocidae whose life cycle is completed largely on or about the sea ice of the Earth's polar regions.

The following are widely considered pagophilic or "ice-loving" species:[1][2]

Subfamily Monachinae

Ross seal

Crabeater seal

Leopard seal

Weddell sealSubfamily Phocinae

Bearded seal

Hooded seal

Harp seal

Ringed seal

Ribbon seal

Spotted seal or larga seal

James Weddell

James Weddell (24 August 1787 in Ostend – 9 September 1834) was a British sailor, navigator and seal hunter who in February 1823 sailed to latitude of 74°15′S (a record 7.69 degrees or 532 statute miles south of the Antarctic Circle) and into a region of the Southern Ocean that later became known as the Weddell Sea.

Knob Point

Knob Point (77°48′S 166°40′E) is a rounded coastal point on the west side of Hut Point Peninsula, Ross Island, Antarctica. The feature lies 1.5 nautical miles (3 km) west of Castle Rock. The name was adopted by the Advisory Committee on Antarctic Names on the recommendation of Gerald L. Kooyman, a United States Antarctic Research Program biologist who studied physiological characteristics related to diving in the Weddell seal in this vicinity, 1963–64 and 1964–65. Kooyman reported that this descriptive name was already in use by other field workers in the area.

Larsen Harbour

Larsen Harbour is a narrow 2.6 miles (4.2 km) long inlet of indenting volcanic rocks and sheeted dykes known as the Larsen Harbour Formation. It is a branch of Drygalski Fjord, entered 2.5 miles (4 km) west-northwest of Nattriss Head, at the southeast end of South Georgia. It was charted by the German Antarctic Expedition, 1911–12, under Filchner, who named it for Captain Carl Anton Larsen a Norwegian Antarctic Explorer, who made significant contributions to the exploration of Antarctica. The most significant being the first discovery of fossils, for which he received the Back Grant from the Royal Geographical Society. Larsen is also considered the founder of the Antarctic whaling industry and the settlement at Grytviken, South Georgia.The peaks and mountain crests surrounding the almost land-locked harbour was described by Sir Ernest Shackleton's photographer Frank Hurley as "most beautiful and exceeding all in grandeur even that of Milford Sound ".The Niall Rankin expedition aboard the Albatross, spent some time here as they studied the Weddell seal colony before going on to Esbensen Bay.The area is rat-free, allowing species such as the South Georgia pipit, and burrowing petrels and prions to thrive. Mountains descend steeply into the sea here, and various glaciers calve into the sea.

Leopard seal

The leopard seal (Hydrurga leptonyx), also referred to as the sea leopard, is the second largest species of seal in the Antarctic (after the southern elephant seal). Its only natural predators are the killer whale. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, birds and fish. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "small clawed".


The true seal tribe Lobodontini, collectively known as the lobodontine seals, consist of four species of seals in four genera: the crabeater seal (Lobodon carcinophaga), the leopard seal (Hydrurga leptonyx), the Weddell seal (Leptonychotes weddelli), and the Ross seal (Ommatophoca rossii). All lobodontine seals have circumpolar distributions surrounding Antarctica. They include both the world's most abundant seal (the crabeater seal) and the only predominantly mammal-eating seal (the leopard seal). While the Weddell seal prefers the shore-fast ice, the other species live primarily on and around the off-shore pack ice. Thus, though they are collectively the most abundant group of seals in the world, the combination of remote range and inaccessible habitat make them among the least well studied of the world's seals.

Lost Seal Stream

Lost Seal Stream (77°36′S 163°15′E) is a glacial meltwater stream, 1.4 nautical miles (2.6 km) long, draining from the west margin of Commonwealth Glacier into the northeast end of Lake Fryxell, in Taylor Valley, Victoria Land, Antarctica. The name was suggested by Diane McKnight, leader of a United States Geological Survey team that studied the hydrology of streams flowing into Lake Fryxell in several seasons, 1987–94, and commemorates the encounter with a living Weddell seal. The seal wandered into the area north of Lake Fryxell during November 1990 and was evacuated by helicopter to New Harbour after it entered the camp area. A mummified seal is prominent at the mouth of the stream.

North-west White Island Antarctic Specially Protected Area

The North-west White Island Antarctic Specially Protected Area comprises a 142 km2 area of coastal shelf ice on the north-west side of White Island in the Ross Archipelago of Antarctica.The site has been designated an Antarctic Specially Protected Area (ASPA 137) because it supports an unusual small breeding population of Weddell seals, which is not only the most southerly known, but which has also been physically isolated from other populations by the advance of the McMurdo and Ross ice shelves. The first seals in the area were recorded in 1958, since when the population has grown to 25–30. The seals use the open waters of McMurdo Sound but do not have the breathing capacity to reach the open ocean by swimming beneath the intervening 20 km of permanent shelf ice.


Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals. They comprise the extant families Odobenidae (whose only living member is the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals). There are 33 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora and their closest living relatives are believed to be bears and the superfamily of musteloids (weasels, raccoons, skunks, and red pandas), having diverged about 50 million years ago.

Seals range in size from the 1 m (3 ft 3 in) and 45 kg (99 lb) Baikal seal to the 5 m (16 ft) and 3,200 kg (7,100 lb) southern elephant seal, which is also the largest member of the order Carnivora. Several species exhibit sexual dimorphism. They have streamlined bodies and four limbs that are modified into flippers. Though not as fast in the water as dolphins, seals are more flexible and agile. Otariids use their front limbs primarily to propel themselves through the water, while phocids and walruses use their hind limbs. Otariids and walruses have hind limbs that can be pulled under the body and used as legs on land. By comparison, terrestrial locomotion by phocids is more cumbersome. Otariids have visible external ears, while phocids and walruses lack these. Pinnipeds have well-developed senses—their eyesight and hearing are adapted for both air and water, and they have an advanced tactile system in their whiskers or vibrissae. Some species are well adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water, and, other than the walrus, all species are covered in fur.

Although pinnipeds are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres. They spend most of their lives in the water, but come ashore to mate, give birth, molt or escape from predators, such as sharks and killer whales. They feed largely on fish and marine invertebrates; but a few, like the leopard seal, feed on large vertebrates, such as penguins and other seals. Walruses are specialized for feeding on bottom-dwelling mollusks. Male pinnipeds typically mate with more than one female (polygyny), although the degree of polygyny varies with the species. The males of land-breeding species tend to mate with a greater number of females than those of ice breeding species. Male pinniped strategies for reproductive success vary between defending females, defending territories that attract females and performing ritual displays or lek mating. Pups are typically born in the spring and summer months and females bear almost all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively short period of time while others take foraging trips at sea between nursing bouts. Walruses are known to nurse their young while at sea. Seals produce a number of vocalizations, notably the barks of California sea lions, the gong-like calls of walruses and the complex songs of Weddell seals.

The meat, blubber and fur coats of pinnipeds have traditionally been used by indigenous peoples of the Arctic. Seals have been depicted in various cultures worldwide. They are commonly kept in captivity and are even sometimes trained to perform tricks and tasks. Once relentlessly hunted by commercial industries for their products, seals and walruses are now protected by international law. The Japanese sea lion and the Caribbean monk seal have become extinct in the past century, while the Mediterranean monk seal and Hawaiian monk seal are ranked endangered by the International Union for Conservation of Nature. Besides hunting, pinnipeds also face threats from accidental trapping, marine pollution, and conflicts with local people.

Ross seal

The Ross seal (Ommatophoca rossii) is a true seal (family Phocidae) with a range confined entirely to the pack ice of Antarctica. It is the only species of the genus Ommatophoca. First described during the Ross expedition in 1841, it is the smallest, least abundant and least well known of the Antarctic pinnipeds. Its distinctive features include disproportionately large eyes, whence its scientific name (Ommato- meaning "eye", and phoca meaning "seal"), and complex, trilling and siren-like vocalizations. Ross seals are brachycephalic, as they have a short broad muzzle and have the shortest fur of any other seal.

Warren Zapol

Warren M. Zapol, MD, is the emeritus Anesthetist-in-Chief at Massachusetts General Hospital and the Reginald Jenney Professor of Anaesthesia at Harvard Medical School. From 1994 to 2008, Dr. Zapol served as anesthetist-in-chief at MGH and is currently the director of the MGH Anesthesia Center for Critical Care Research. A graduate of Massachusetts Institute of Technology “MIT” (1962) and the University of Rochester School of Medicine (1966), Dr. Zapol’s major research efforts include studies of acute respiratory failure in animals and humans. Supported by the National Science Foundation, he has led nine Antarctic expeditions to study the diving mechanisms and adaptations of the Weddell seal. Through that research his team learned how marine mammals avoid the bends and hypoxia (low blood oxygen levels). He was elected to membership in the (then) Institute of Medicine of the National Academy of Science in 2002. In 2003, he was awarded the Intellectual Property Owners Association’s Inventor of the Year Award for the treatment of hypoxic human newborns with inhaled nitric oxide, a technique now used to save the lives of thousands of babies each year that he pioneered with his MGH team. In 2006, a steep mountain glacier in Antarctica was named for Dr. Zapol (78° 35’S, 85° 51’W). In 2008, he was appointed by President George W. Bush and in 2012 reappointed by President Barack Obama as an academic representative to the U.S. Arctic Research Commission. In 2010 he presented the John W. Severinghaus Lecture on Translational Research at the American Society of Anesthesiologists Annual Meeting. In 2012, he was designated as a Distinguished Scientist by the American Heart Association In 2014, Dr. Zapol together with his son David Zapol founded Third Pole Therapeutics, a US-based company developing next generation life-saving heart and lung therapies. The company is developing products that will generate and deliver electric nitric oxide. Dr. Zapol was inducted as a Fellow by the National Academy of Inventors in 2016.

Extant Carnivora species

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