46-689: Monachinae (known colloquially as " Southern seals ") is a subfamily of Phocidae whose distribution is found in the tropical , temperate and polar regions of the southern hemisphere , though in the distant past fossil representatives have been found on both sides of the North Atlantic Ocean . The difference between members of this group and members of Phocinae is in monachines the hindclaws are greatly reduced in size. Furthermore, all species have 34 chromosomes . There are three tribes recognized here: Monachini (monk seals), Miroungini (elephant seals), and Lobodontini (Antarctic seals and
92-485: A day, and by 6–7 weeks old they can weigh around 100 kg (220 lb). 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 . In the winter, they stay in the water to avoid blizzards , with only their heads poking through breathing holes in the ice. These seals are often observed lying on their sides when on land. Weddell seals are non-migratory phocids that move regionally to follow
138-660: A day, while an active adult eats over 50 kg (110 lb) a day. Antarctic cod and silverfish 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 . Although seabirds are not usually part of their diet, there have been several sightings of them chasing and killing penguins in
184-491: A diel dive pattern, diving deeper and longer during the day than at night. 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. Weddell seals are top predators in the Antarctic. They eat an array of fish , bottom-feeding prawns , cephalopods and crustaceans . A sedentary adult eats around 10 kg (22 lb)
230-467: A handful of Afroamerican fossil genera). While today represented by eight extant and one recently extinct species , Monachinae had an incredibly enriched fossil diversity that went into decline soon to be replaced by southern species of sea lions and fur seals . [REDACTED] This article about a carnivoran is a stub . You can help Misplaced Pages by expanding it . Earless seal The earless seals , phocids , or true seals are one of
276-628: A long time underwater between breaths. Air is forced from the lungs during a dive and into the upper respiratory passages, where gases cannot easily be absorbed into the bloodstream. This helps protect the seal from the bends . The middle ear is also lined with blood sinuses that inflate during diving, helping to maintain a constant pressure. Phocids are more specialized for aquatic life than otariids. They lack external ears and have sleek, streamlined bodies. Retractable nipples , internal testicles , and an internal penile sheath provide further streamlining. A smooth layer of blubber lies underneath
322-458: A monophyletic origin for all pinnipeds from a single ancestor, possibly Enaliarctos , most closely related to the mustelids and bears . Monk seals and elephant seals were previously believed to have first entered the Pacific through the open straits between North and South America, with the Antarctic true seals either using the same route or travelled down the west coast of Africa. It
368-439: A short period. This allows the mother to return to the sea in time to replenish her reserves. Lactation ranges from five to seven weeks in the monk seal to just three to five days in the hooded seal . The mother ends nursing by leaving her pup at the breeding site to search for food (pups continue to nurse if given the opportunity). "Milk stealers" that suckle from unrelated, sleeping females are not uncommon; this often results in
414-401: A thin fur coat around its whole body except for small areas around the flippers. The colour and pattern of the coat vary, often fading to a duller colour as the seal ages. This coat moults around the beginning of summer . Adults show a counter-shaded colouration that varies from bluish-black to dark grey dorsally and to light grey/silver ventrally. Coats may change to shades of brown before
460-589: Is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica . The Weddell seal was discovered and named in the 1820s during expeditions led by British sealing captain James Weddell to the area of the Southern Ocean now known as the Weddell Sea . The life history of this species is well documented since it occupies fast ice environments close to
506-466: Is aided by a specialized skull, mandible, and tooth morphology. However, despite morphological specialization, most phocids are opportunistic and employ multiple strategies to capture and eat prey. For example, the leopard seal, Hydrurga leptonyx , uses grip and tear feeding to prey on penguins, suction feeding to consume small fish, and filter feeding to catch krill. [REDACTED] Weddell seal The Weddell seal ( Leptonychotes weddellii )
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#1732772049332552-670: 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. 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. Weddell seals return to fast ice colonies during
598-418: Is not implanted into the uterus until the beginning of austral summer , between mid-January and mid-February, allowing for birth under more favourable environmental conditions. Juvenile Weddell seals (0–2 years old) have a high mortality probability, whereas no differences can be found between the mortality rate of animals older than 2 years and that of adults (Hastings et al., 1999). The maximum lifespan of
644-616: Is now thought that the monk seals , elephant seals , and Antarctic seals all evolved in the southern hemisphere, and likely dispersed to their current distributions from more southern latitudes. Bearded seal Hooded seal Ringed seal Baikal seal Caspian seal Spotted seal Harbor seal Grey seal Ribbon seal Harp seal Weddell seal Leopard seal Crabeater seal Ross seal Southern elephant seal Northern elephant seal Mediterranean monk seal Hawaiian monk seal Caribbean monk seal Otariidae ( eared seals ) Odobenidae ( Walrus ) In
690-555: Is the only species of exclusively freshwater seal . The earliest known fossil earless seal is Noriphoca gaudini from the late Oligocene or earliest Miocene ( Aquitanian ) of Italy . Other early fossil phocids date from the mid-Miocene, 15 million years ago in the north Atlantic. Until recently, many researchers believed that phocids evolved separately from otariids and odobenids ; and that they evolved from otter -like animals, such as Potamotherium , which inhabited European freshwater lakes. Recent evidence strongly suggests
736-577: The Antarctic continent and often adjacent to Antarctic bases. It is the only species in the genus Leptonychotes . 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). They are amongst the largest seals, with a rather bulky body and short fore flippers relative to their body length . Males weigh less than females, usually about 500 kg (1,100 lb) or less. Male and female Weddell seals are generally about
782-480: The pelvis in such a way that they cannot bring them under their bodies to walk on them. They are more streamlined than fur seals and sea lions, so they can swim more effectively over long distances. However, because they cannot turn their hind flippers downward, they are very clumsy on land, having to wriggle with their front flippers and abdominal muscles . Phocid respiratory and circulatory systems are adapted to allow diving to considerable depths, and they can spend
828-459: The tribe Lobodontini . Tribe Miroungini is composed of the elephant seals . The Monk seals ( Monachus and Neomonachus ) are all part of the tribe Monachini. Likewise, subfamily Phocinae (the "northern" seals) also includes three tribes; Erignathini ( Erignathus ) , Cystophorini ( Cystophora) , and Phocini (all other phocines). More recently, five species have been split off from Phoca , forming three additional genera. Alternatively
874-571: The 1980s and 1990s, morphological phylogenetic analysis of the phocids led to new conclusions about the interrelatedness of the various genera. More recent molecular phylogenetic analyses have confirmed the monophyly of the two phocid subfamilies ( Phocinae and Monachinae). The Monachinae (known as the "southern" seals), is composed of three tribes; the Lobodontini, Miroungini, and Monachini. The four Antarctic genera Hydrurga , Leptonychotes , Lobodon , and Ommatophoca are part of
920-673: The ability of the species to colonise different environments, although the extent of such plasticity is uncertain. In the past, the establishment of Antarctic research bases has caused a measure of disturbance to these seals. In January 1998 the Environmental Protection Protocol to the Antarctic Treaty was ratified, implementing environmental measures such as the banning of mining and oil drilling in Antarctica for at least 50 years, along with
966-399: The annual moult. Adult males usually bear scars, most of them around the genital region. Weddell seal pups are born with a lanugo of similar colouration and they moult after 3–4 weeks; later, they turn a darker colour similar to that of adults. 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)
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#17327720493321012-527: The availability of higher-resolution satellite imagery and crowdsourced data, future counts may be simplified with automated image recognition. During the early periods of Antarctic exploration , Weddell seals suffered dramatic declines as they were hunted for food and oil. Populations have since recovered after the elimination of commercial sealing in the 1980s. However, the effects of global climate change on Antarctic seals are still to be fully determined. Research estimates seal populations may decline as
1058-468: The availability of their habitat is extremely temperature sensitive thus making them potentially vulnerable . Climate changes affecting the duration and the extent of the sea ice and nutrient availability could potentially reduce pups’ survival and may have important implications for population growth rates . The fact that some populations breed on land (e.g., in South Georgia ), could demonstrate
1104-416: The banning of refuse disposal and the use of pesticides in the region. However, the disturbance effects of the increasing seasonal tourism in the Antarctic and Sub-Antarctic on Weddell seal behaviour, distribution, and foraging are still unknown. Currently, there are no reports of significant fisheries interactions. Although, the development of new fisheries in Antarctic waters, particularly one targeting
1150-411: The breeding site to use their stored energy to nurse pups. However, the common seal displays a reproductive strategy similar to that used by otariids , in which the mother makes short foraging trips between nursing bouts. Because a phocid mother's feeding grounds are often hundreds of kilometers from the breeding site, she must fast while lactating . This combination of fasting with lactation requires
1196-489: The death of the mother's pup, since a female can only feed one pup. The pup's diet is so high in calories that it builds up a fat store. Before the pup is ready to forage, the mother abandons it, and the pup consumes its own fat for weeks or even months while it matures. Seals, like all marine mammals, need time to develop the oxygen stores, swimming muscles, and neural pathways necessary for effective diving and foraging. Seal pups typically eat no food and drink no water during
1242-465: The distribution of breathing holes and exit cracks within the ice changes between seasons. The species is primarily restricted to Antarctic waters: physical factors, such as glacial movement and tidal action , may increase fluctuations in distributions. Weddell seals dive to forage for food, maintain breathing holes in fast ice, and explore to find more ice holes. They have been observed to dive as deep as 600 m for up to an hour. These seals exhibit
1288-465: The functional significance of these high-frequency sounds is yet unknown. Rice noted that the scientific name was misspelt in the past as L. weddelli and this synonym is no longer accepted, although it is still found commonly in the scientific literature before 1988. Weddell seals can be confused with other two phocids that share the same range: Ross seal ( Ommatophoca rossii ) and crabeater seal ( Lobodon carcinophagus ). Weddell seals are
1334-803: The ice itself or from water to breathing holes where female Weddell seals are usually breeding. There have been recordings of Weddell seal vocalisations 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 unique song , but singing behaviour is not common when observed. Vocalisations are also important in mother-pup Weddell seal interactions. Mother Weddell seals use vocalisations to call their pups from further distances when smell can no longer be used efficiently (Opzeeland et al., 2011). Pups also use higher, more urgent vocalisations when hungry to alert their mothers to feed. Weddell seals commonly produce ultrasonic vocalizations. However,
1380-595: The mating season, Weddell seals make noises loud enough to be felt through the ice. Males defend underwater territories during the breeding season and have been observed to fight. Copulation has only been observed to occur underwater, 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. The seals are normally around six to eight years old when they first breed, but this can be much earlier for some females. Weddell seals undergo delayed implantation . The embryo
1426-480: The mother to provide large amounts of energy to her pup at a time when she is not eating (and often, not drinking). Mothers must supply their own metabolic needs while nursing. This is a miniature version of the humpback whales ' strategy, which involves fasting during their months-long migration from arctic feeding areas to tropical breeding/nursing areas and back. Phocids produce thick, fat-rich milk that allows them to provide their pups with large amounts of energy in
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1472-460: The muscle, which may serve a thermogenic role. Male and female Weddell seals communicate through a variety of sounds, specifically, males sometimes use “trills” to communicate. Weddell seals are also able to communicate with each other through different mediums. Weddell seals on ice can hear the calls of Weddell seals in the water as long as the noise level on land is low and they are nearby of one another. Sound waves can be transmitted either through
1518-490: The muscles of newborn Weddell seals, suggesting that a primary thermoregulatory strategy of these seals includes muscle thermogenesis, or shivering. The activity of metabolic enzymes including citrate synthase , ß-hydroxyacyl CoA dehydrogenase, and cytochrome c oxidase were measured and determined to be significantly active in newborn Weddell seals' longissimus dorsi, a large and major swimming muscle. Research has also suggested that pups have high mitochondrial densities in
1564-432: The only species of seals that can give birth to twin pups. Birthing of the pup takes only one to four minutes. Newborn pups weigh about 25–30 kg and grow to two times their weight within their first week of life. The pups take their first swim around one to two weeks of age. During the first two weeks, mother Weddell seals distinguish their pups through olfactory smells, and specialised vocalisations , and stay in
1610-733: The order Carnivora . Phocids have fewer teeth than land-based members of the Carnivora , although they retain powerful canines . Some species lack molars altogether. The dental formula is: 2–3.1.4.0–2 1–2.1.4.0–2 While otariids are known for speed and maneuverability, phocids are known for efficient, economical movement. This allows most phocids to forage far from land to exploit prey resources, while otariids are tied to rich upwelling zones close to breeding sites. Phocids swim by sideways movements of their bodies, using their hind flippers to fullest effect. Their fore flippers are used primarily for steering, while their hind flippers are bound to
1656-523: The period, although some polar species eat snow. The postweaning fast ranges from two weeks in the hooded seal to 9–12 weeks in the northern elephant seal. The physiological and behavioral adaptations that allow phocid pups to endure these remarkable fasts, which are among the longest for any mammal, remain an area of active study and research. Phocids make use of at least four different feeding strategies: suction feeding, grip and tear feeding, filter feeding, and pierce feeding. Each of these feeding strategies
1702-411: The ratio skews towards females with increasing age. Previous estimates, with lower geographic coverage and thus relying more heavily on extrapolations, tended to be much higher, reporting numbers in the range of 800,000 or so. Because of the widespread distribution of Weddell seals, population assessments are difficult and expensive to conduct, and therefore infrequently undertaken. However, thanks to
1748-446: The same length, though females can be slightly larger. However, the male seal tends to have a thicker neck and a broader head and muzzle than the female. A molecular genetic-based technique has been established to confirm the sex of individuals in the laboratory . 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 . The Weddell seal grows
1794-594: The same spatial area. After six to seven weeks, pups are weaned and begin to hunt independently. Weddell seals show moderate polygyny and genetic analyses of mating success have suggested how factors such as size , diving ability, and site-specific experience enhance success in male Weddell seals. Additionally, fast ice breeding grounds cause females to cluster in large aggregations, making it easier for males to control their harem . The mating season occurs during austral spring between late November and December after pups are weaned and females begin ovulating. During
1840-486: The second most abundant species of Antarctic phocid, after the crabeater seal. The most recent estimate suggests a population of about 202,000 female seals, based on high-resolution satellite images from November 2011 that cover the full habitat range of the species. This number includes females only, as males are mostly underwater guarding their territories in November. There are likely to be fewer males than females, as
1886-432: The skin. Phocids are able to divert blood flow to this layer to help control their temperatures. Unlike otariids, true seals do not communicate by 'barking'. Instead, they communicate by slapping the water and grunting. Phocids spend most of their time at sea, although they return to land or pack ice to breed and give birth. Pregnant females spend long periods foraging at sea, building up fat reserves, and then return to
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1932-413: The species is estimated at least 25 years. Newborn Weddell seals have different thermoregulatory strategies from other species of seals. Weddell seal pups are not born with brown fat , which is used in other seal species for thermoregulation. Instead, they rely heavily on lanugo , a fine layer of hair on the surface of their skin, to keep warm. Studies also revealed high levels of enzyme activity in
1978-407: The spring for birthing and breeding . Weddell seal populations will often return to the same breeding sites over consecutive breeding seasons. 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. Weddell seals usually give birth to one pup per year, however the Weddell seal is one of
2024-481: The three main groups of mammals within the seal lineage, Pinnipedia . All true seals are members of the family Phocidae ( / ˈ f oʊ s ɪ d iː / ). 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
2070-400: The three monachine tribes have been evaluated to familiar status, which elephant seals and the Antarctic seals are more closely related to the phocines. Adult phocids vary from 1.17 m (3.8 ft) in length and 45 kg (99 lb) in weight in the ringed seal to 5.8 m (19 ft) and 4,000 kg (8,800 lb) in the southern elephant seal , which is the largest member of
2116-493: The wild. Other Antarctic phocids are known to be seabird predators, resulting in implications that penguin hunting is a learned behaviour. There are recordings of four different penguin species being attacked by Weddell seals: a gentoo penguin , an emperor penguin , an Adélie penguin , and a chinstrap penguin . It has not been confirmed, however, if the penguins were consumed after being killed. Scientists believe Weddell seals rely mainly on eyesight to hunt for food when there
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