Earless seal – Wikipedia

family of mammals

The earless seals, phocids or true seals are one of the three main groups of mammals within the seal descent, Pinnipedia. All genuine seals are members of the kin 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 largely confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of entirely fresh water seal .

Taxonomy and development [edit ]

evolution [edit ]

Pliophoca skull Fossilskull

The earliest know dodo earless seal is Noriphoca gaudini from the late Oligocene or earliest Miocene ( Aquitanian ) of Italy. [ 1 ] other early fossil phocids date from the mid-Miocene, 15 million years ago in the north Atlantic. [ 1 ] [ 3 ] Until recently, many researchers believed that phocids evolved individually from otariids and odobenids ; and that they evolved from otter -like animals, such as Potamotherium, which inhabited european fresh water lakes. late tell powerfully suggests a monophyletic origin for all pinnipeds from a single ancestor, possibly Enaliarctos, most close related to the mustelids and bears. [ 4 ] Monk seals and elephant seals were previously believed to have beginning entered the Pacific through the open straits between North and South America, [ 5 ] with the Antarctic true seals either using the lapp path or travelled down the west coast of Africa. [ 6 ] It is now thought that the monk seals, elephant seals, and south-polar seals all evolved in the southern hemisphere, and probable dispersed to their current distributions from more southern latitudes. [ 7 ]

taxonomy [edit ]

In the 1980s and 1990s, morphologic phylogenetic analysis of the phocids led to new conclusions about the interrelation of the respective genus. More recent molecular phylogenetic analyses have confirmed the monophyly of the two phocid subfamilies ( Phocinae and Monachinae ). [ 9 ] [ 10 ] [ 11 ] [ 5 ] The Monachinae ( known as the “ southern ” seals ), is composed of three tribes ; the Lobodontini, Miroungini, and Monachini. The four Antarctic genus Hydrurga, Leptonychotes, Lobodon, and Ommatophoca are part of the tribe Lobodontini. Tribe Miroungini is composed of the elephant seals. The Monk seals ( Monachus and Neomonachus ) are all part of the tribe Monachini. [ 12 ] Likewise, subfamily Phocinae ( the “ northerly ” seals ) besides includes three tribe ; Erignathini ( Erignathus), Cystophorini ( Cystophora), and Phocini ( all other phocines ). More recently, five species have been split off from Phoca, forming three extra genus. [ 13 ] alternatively the three monachine tribes have been evaluated to familiar status, which elephant seals and the antarctic seals are more closely related to the phocines. [ 14 ]

extant genus [edit ]

biology [edit ]

external anatomy [edit ]

skeletal anatomy of a harbor seal. 1. Skull. 2. Spine. 3. Tail. 4. Hindlimb. 5. Forelimb. 6. shoulder. 7. Pelvis. 8. Rib cage. Adult phocids vary from 1.17 meter ( 3.8 foot ) in length and 45 kilogram ( 99 pound ) in burden in the ringed seal to 5.8 thousand ( 19 foot ) and 4,000 kilogram ( 8,800 pound ) in the southerly elephant seal, which is the largest member of the arrange Carnivora. Phocids have fewer teeth than land-based members of the Carnivora, although they retain potent canines. Some species lack molars all in all. The dental formula is : 2––21––2 While otariids are known for amphetamine and maneuverability, phocids are known for efficient, economic motion. This allows most phocids to forage far from domain to exploit prey resources, while otariids are tied to rich upwelling zones near to breeding sites. Phocids swim by sideway movements of their bodies, using their hind flippers to fullest consequence. [ 15 ] Their fore flippers are used primarily for steering, while their hind flippers are bound to the pelvis in such a means that they can not bring them under their bodies to walk on them. They are more streamlined than fur seals and sea lions, so they can swim more efficaciously over long distances. however, because they can not turn their hind flippers down, they are very bungling on farming, having to wriggle with their front flippers and abdominal muscles .
Seal kidney Phocid respiratory and circulative systems are adapted to allow diving to considerable depths, and they can spend a hanker meter subaqueous between breaths. Air is forced from the lungs during a dive and into the upper respiratory passages, where gases can not easily be absorbed into the bloodstream. This helps protect the navy seal from the bends. The middle ear is besides lined with blood sinuses that inflate during dive, helping to maintain a ceaseless pressure. [ 15 ] Phocids are more speciate for aquatic life than otariids. They lack external ears and have sleek, streamline bodies. retractable nipples, inner testicles, [ 16 ] and an home penile sheath provide far streamlining. A smooth layer of snivel lies underneath the skin. Phocids are able to divert blood flow to this layer to help control their temperatures. [ 17 ]

communication [edit ]

Unlike otariids, true seals do not communicate by ‘barking ‘. alternatively, they communicate by slapping the water and grunt.

reproduction [edit ]

Photo of seven adult and juvenile southern elephant seals packed closely on beach Southern elephant seals in Argentina Phocids spend most of their meter at sea, although they return to land or pack ice to breed and give birth. meaning females spend long periods foraging at sea, building up fat reserves, and then return to the breed site to use their store energy to nurse pups. however, the common sealing wax displays a generative strategy like to that used by otariids, in which the mother makes short foraging trips between nurse bouts. Because a phocid mother ‘s feed grounds are much hundreds of kilometers from the education site, she must fast while lactating. This combination of fasting with suckling requires the mother to provide large amounts of energy to her whelp at a prison term when she is not eat ( and frequently, not drinking ). Mothers must supply their own metabolic needs while nurse. This is a miniature version of the kyphosis whales ‘ scheme, which involves fasting during their months-long migration from arctic feeding areas to tropical breeding/nursing areas and back. Phocids produce slurred, fat-rich milk that allows them to provide their pups with big amounts of energy in a short menstruation. 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 barely three to five days in the hood seal. The beget ends nursing by leaving her puppy at the breeding web site to search for food ( pups continue to nurse if given the opportunity ). “ milk stealers ” that suckle from unrelated, dormant females are not uncommon ; this often results in the end of the mother ‘s puppy, since a female can only feed one puppy .

Growth and maturation [edit ]

The pup ‘s diet is thus high gear in calories, it builds up a fat storehouse. Before the whelp is fix to forage, the mother abandons it, and the whelp consumes its own fat for weeks or flush months while it matures. Seals, like all marine mammals, need time to develop the oxygen stores, swimming muscles, and neural pathways necessity for effective dive and foraging. Seal pups typically eat no food and drink no water during the menstruation, although some polar species eat bamboozle. The postweaning fast ranges from two weeks in the hood sealing wax to 9–12 weeks in the northern elephant sealing wax. [ 19 ] The physiological and behavioral adaptations that allow phocid pups to endure these noteworthy fasts, which are among the longest for any mammal, remain an area of active voice study and research .

Feeding scheme [edit ]

Phocids make habit of at least four different feeding strategies : suction feed, handle, and tear feed, filter feed, and pierce feeding. Each of these feeding strategies is aided by a specialize skull, lower jaw, and tooth morphology. however, despite geomorphologic specialization, most phocids are opportunist and hire multiple strategies to capture and eat prey. For case, the leopard seal, Hydrurga leptonyx, uses grip and tear feeding to prey on penguins, suction feed to consume small pisces, and trickle feeding to catch krill. [ 20 ]

See besides [edit ]

References [edit ]

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