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 /ˈfoʊsɪdiː/. 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.

Earless seals[2]
Temporal range: Aquitanian–present
Early MioceneHolocene, possible late Oligocene record[1]
Seehund
Harbor seal, Phoca vitulina
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Superfamily: Phocoidea
Family: Phocidae
Gray, 1821
Genera

Taxonomy

Phylogeny

In the 1980s, phylogenetic analysis of the phocids led to new conclusions about the interrelatedness of the various genera. The four genera Hydrurga, Leptonychotes, Lobodon, and Ommatophoca form a monophyletic group, the tribe Lobodontini. Likewise, the Phocinae subfamily (Erignathus, Cystophora, and Phocini) is also monophyletic. More recently, five species have been split off from Phoca, forming three additional genera. However, the subfamily Monachinae (the lobodonts Mirounga) is probably paraphyletic.[2]

Cranio Pliophoca etrusca, Orciano
Fossil Pliophoca skull

Superfamily Pinnipedia

Phocidae

ringed seal

Baikal seal

Caspian seal

spotted seal

harbor seal

grey seal

ribbon seal

harp seal

hooded seal

bearded seal

Weddell seal

leopard seal

crabeater seal

Ross seal

southern elephant seal

northern elephant seal

Mediterranean monk seal

Hawaiian monk seal

Cladogram showing relationships among the extant earless seals, combining several phylogenetic analyses.[4]

Evolution

Piscophoca pacifica
Piscophoca pacifica fossil

The earliest known fossil 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. 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 a monophyletic origin for all pinnipeds from a single ancestor, possibly Enaliarctos, most closely related to the bears.

Monk seals and elephant seals are believed to have first entered the Pacific through the open straits between North and South America, which only closed in the Pliocene. The various Antarctic species may have either used the same route, or traveled down the west coast of Africa.[5]

Biology

External anatomy

Phoca vitulina 02 MWNH 1464
Harbor seal skull (Phoca vitulina)

Adult phocids vary from 1.17 m (3.8 ft) in length and 45 kg (99 lb) in weight in the ringed seal to 4.9 m (16 ft) and 2,400 kg (5,300 lb) in land-based members of the Carnivora, although they retain powerful canines. Some species lack molars altogether. The dental formula is: 2–3.1.4.0–21–2.1.4.0–2

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.[6] Their fore flippers are used primarily for steering, while their hind flippers are bound to 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 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.

Seal kidney-- FMVZ USP-08
Seal kidney

Phocid respiratory and circulatory systems are adapted to allow diving to considerable depths, and they can spend 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.[6]

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 the skin. Phocids are able to divert blood flow to this layer to help control their temperatures.

Communication

Unlike otariids, true seals do not communicate by 'barking'. Instead, they communicate by slapping the water and grunting.

Reproduction

Earless seal (Puerto Madryn, Argentina)
Southern elephant seals in Argentina

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 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 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 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 the death of the mother's pup, since a female can only feed one pup.

Growth and maturation

The pup's diet is so high in calories, 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 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.[7] 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.

See also

References

  1. ^ a b Leonard Dewaele; Olivier Lambert; Stephen Louwye (2018). "A critical revision of the fossil record, stratigraphy and diversity of the Neogene seal genus Monotherium (Carnivora, Phocidae)". Royal Society Open Science. 5 (5): 171669. doi:10.1098/rsos.171669. PMC 5990722. PMID 29892365.
  2. ^ a b Wozencraft, W.C. (2005). "Order Carnivora". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. OCLC 62265494.
  3. ^ Peter Saundry. 2010. True Seals. Encyclopedia of Earth. topic ed. C.Michael Hogan, ed. in chief C.Cleveland, National Center for Science and the Environment, Washington DC
  4. ^ Berta, A.; Churchill, M. (2012). "Pinniped taxonomy: Review of currently recognized species and subspecies, and evidence used for their description". Mammal Review. 42 (3): 207–34. doi:10.1111/j.1365-2907.2011.00193.x.
  5. ^ Savage, RJG & Long, MR (1986). Mammal Evolution: an illustrated guide. New York: Facts on File. pp. 94–95. ISBN 978-0-8160-1194-0.
  6. ^ a b McLaren, Ian (1984). Macdonald, D. (ed.). The Encyclopedia of Mammals. New York: Facts on File. pp. 270–275. ISBN 978-0-87196-871-5.
  7. ^ Costa, D. P.; Boeuf, B. J. Le; Huntley, A. C.; Ortiz, C. L. (1986-03-01). "The energetics of lactation in the Northern elephant seal, Mirounga angustirostris". Journal of Zoology. 209 (1): 21–33. doi:10.1111/j.1469-7998.1986.tb03563.x. ISSN 1469-7998.
2013 in mammal paleontology

This article records new taxa of fossil mammals of every kind that have been described during the year 2013, as well as other significant discoveries and events related to paleontology of mammals that occurred in the year 2013.

2014 in mammal paleontology

This article records new taxa of fossil mammals of every kind that have been described during the year 2014, as well as other significant discoveries and events related to paleontology of mammals that occurred in the year 2014.

2015 in paleontology

Paleontology or palaeontology (from Greek: paleo, "ancient"; ontos, "being"; and logos, "knowledge") is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2015.

Afrophoca

Afrophoca is an extinct genus of earless seal from Miocene-age marine deposits in Libya.

Aquatic mammal

Aquatic and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the European otter. They are not a taxon and are not unified by any distinct biological grouping, but rather their dependence on and integral relation to aquatic ecosystems. The level of dependence on aquatic life varies greatly among species. Among freshwater taxa, the Amazonian manatee and river dolphins are completely aquatic and fully dependent on aquatic ecosystems. Semiaquatic freshwater taxa include the Baikal seal, which feeds underwater but rests, molts, and breeds on land; and the capybara and hippopotamus which are able to venture in and out of water in search of food.

Mammal adaptation to an aquatic lifestyle vary considerably between species. River dolphins and manatees are both fully aquatic and therefore are completely tethered to a life in the water. Seals are semiaquatic; they spend the majority of their time in the water, but need to return to land for important activities such as mating, breeding and molting. In contrast, many other aquatic mammals, such as hippopotamus, capybara, and water shrews, are much less adapted to aquatic living. Likewise, their diet ranges considerably as well, anywhere from aquatic plants and leaves to small fish and crustaceans. They play major roles in maintaining aquatic ecosystems, beavers especially.

Aquatic mammals were the target for commercial industry, leading to a sharp decline in all populations of exploited species, such as beavers. Their pelts, suited for conserving heat, were taken during the fur trade and made into coats and hats. Other aquatic mammals, such as the Indian rhinoceros, were targets for sport hunting and had a sharp population decline in the 1900s. After it was made illegal, many aquatic mammals became subject to poaching. Other than hunting, aquatic mammals can be killed as bycatch from fisheries, where they become entangled in fixed netting and drown or starve. Increased river traffic, most notably in the Yangtze river, causes collisions between fast ocean vessels and aquatic mammals, and damming of rivers may land migratory aquatic mammals in unsuitable areas or destroy habitat upstream. The industrialization of rivers led to the extinction of the Chinese river dolphin, with the last confirmed sighting in 2004.

Baikal seal

The Baikal seal, Lake Baikal seal or nerpa (Pusa sibirica), is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seals and the only exclusively freshwater pinniped species. A subpopulation of inland harbour seals living in the Hudson's Bay region of Quebec, Canada (lac de loups marins harbour seals), the Saimaa ringed seal (a ringed seal subspecies) and the Ladoga seal (a ringed seal subspecies) are found in fresh water, but these are part of species that also have marine populations.The most recent population estimates are 80,000 to 100,000 animals, roughly equaling the expected carrying capacity of the lake. At present, the species is not considered threatened, despite hunting (both legal and illegal) and pollution of the lake.

Baptornis

Baptornis ("diving bird") is a genus of flightless aquatic birds from the Late Cretaceous, some 87-80 million years ago (roughly mid-Coniacian to mid-Campanian faunal stages). The fossils of Baptornis advenus, the type species, were discovered in Kansas, which at its time was mostly covered by the Western Interior Seaway, a shallow shelf sea. It is now known to have also occurred in today's Sweden, where the Turgai Strait joined the ancient North Sea; possibly, it occurred in the entire Holarctic.

Othniel Charles Marsh discovered the first fossils of this bird in the 1870s. This was, alongside the Archaeopteryx, one of the first Mesozoic birds to become known to science.

Bearded seal

The bearded seal (Erignathus barbatus), also called the square flipper seal, is a medium-sized pinniped that is found in and near to the Arctic Ocean. It gets its generic name from two Greek words (eri and gnathos) that refer to its heavy jaw. The other part of its Linnaean name means bearded and refers to its most characteristic feature, the conspicuous and very abundant whiskers. When dry, these whiskers curl very elegantly, giving the bearded seal a "raffish" look.Bearded seals are the largest northern phocid. They have been found to weigh as much as much as 300 kg with the females being the largest. However, male and female bearded seals are not very dimorphic.The only member of the genus Erignathus, the bearded seal is unique in that it is an intermediate. Bearded seals belong to the family Phocidae which contains two subfamilies: Phocinae and Monachinae. The bearded seal possesses characteristics of both of these subfamilies.Fossils first described in 2002 indicated that, during the Pleistocene epoch, bearded seals ranged as far south as South Carolina.

Caspian seal

The Caspian seal (Pusa caspica) is one of the smallest members of the earless seal family and unique in that it is found exclusively in the brackish Caspian Sea. They are found not only along the shorelines, but also on the many rocky islands and floating blocks of ice that dot the Caspian Sea. In winter, and cooler parts of the spring and autumn season, these marine mammals populate the Northern Caspian. As the ice melts in the warmer season, they can be found on the mouths of the Volga and Ural Rivers, as well as the southern latitudes of the Caspian where cooler waters can be found due to greater depth.

Evidence suggests the seals are descended from Arctic ringed seals that reached the area from the north during an earlier part of the Quaternary period and became isolated in the landlocked Caspian Sea when continental ice sheets melted.

Harp seal

The harp seal or saddleback seal, Pagophilus groenlandicus is a species of earless seal, or true seal, native to the northernmost Atlantic Ocean and Arctic Ocean. Originally in the genus Phoca with a number of other species, it was reclassified into the monotypic genus Pagophilus in 1844. In Latin, its scientific name translates to "ice-lover from Greenland," and its taxonomic synonym, Phoca groenlandica translates to "Greenlandic seal."

Hawaiian monk seal

The Hawaiian monk seal, Neomonachus schauinslandi (formerly Monachus schauinslandi), is an endangered species of earless seal in the family Phocidae that is endemic to the Hawaiian Islands.The Hawaiian monk seal is one of two remaining monk seal species; the other is the Mediterranean monk seal. A third species, the Caribbean monk seal, is extinct.The Hawaiian monk seal is the only seal native to Hawaii, and, along with the Hawaiian hoary bat, is one of only two mammals endemic to the islands.These monk seals are a conservation reliant endangered species. The small population of about 1,400 individuals is threatened by human encroachment, very low levels of genetic variation, entanglement in fishing nets, marine debris, disease, and past commercial hunting for skins. There are many methods of conservation biology when it comes to endangered species; translocation, captive care, habitat cleanup, and educating the public about the Hawaiian monk seal are some of the methods that can be employed.

List of the Cenozoic life of Alaska

This list of the Cenozoic life of Alaska contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Alaska and are between 66 million and 10,000 years of age.

List of the Cenozoic life of New Jersey

This list of the Cenozoic life of New Jersey contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of New Jersey and are between 66 million and 10,000 years of age.

List of the Cenozoic life of South Carolina

This list of the Cenozoic life of South Carolina contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of South Carolina and are between 66 million and 10,000 years of age.

Monk seal

Monk seals are earless seals of the tribe Monachini. They are the only earless seals found in tropical climates. The two genera of monk seals, Monachus and Neomonachus, comprise three species: the Mediterranean monk seal, Monachus monachus; the Hawaiian monk seal, Neomonachus schauinslandi; and the Caribbean monk seal, Neomonachus tropicalis, which became extinct in the 20th century. The two surviving species are now rare and in imminent danger of extinction. All three monk seal species were classified in genus Monachus until 2014, when the Caribbean and Hawaiian species were placed into a new genus, Neomonachus.

Monk seals have a slender body and are agile. They have a broad, flat snout with nostrils on the top. Monk seals are polygynous, and group together in harems. They feed mainly on bony fish and cephalopods, but they are opportunistic. The skin is covered in small hairs, which are generally black in males and brown or dark gray in females. Monk seals are found in the Hawaiian archipelago, certain areas in the Mediterranean Sea (such as Cabo Blanco and Gyaros island), and formerly in the tropical areas of the west Atlantic Ocean.

All species experienced overhunting by sealers. The Hawaiian monk seal experienced population drops in the 19th century and during World War II, and the Caribbean monk seal was exploited since the 1500s until the 1850s, when populations were too low to hunt commercially. The Mediterranean monk seal has experienced commercial hunting since the Middle Ages and eradication by fishermen. Monk seals have developed a fear of humans, and may even abandon beaches due to human presence. Currently, around 1,700 monk seals remain.

Polk County, Florida paleontological sites

The Polk County paleontological sites are assemblages of Early Miocene to Late Pleistocene vertebrates occurring in Polk County, Florida, United States.

Quebec

Quebec ( (listen); French: Québec [kebɛk] (listen)) is one of the thirteen provinces and territories of Canada. It is bordered to the west by the province of Ontario and the bodies of water James Bay and Hudson Bay; to the north by Hudson Strait and Ungava Bay; to the east by the Gulf of Saint Lawrence and the province of Newfoundland and Labrador; and to the south by the province of New Brunswick and the U.S. states of Maine, New Hampshire, Vermont, and New York. It also shares maritime borders with Nunavut, Prince Edward Island, and Nova Scotia. Quebec is Canada's largest province by area and its second-largest administrative division; only the territory of Nunavut is larger. It is historically and politically considered to be part of Central Canada (with Ontario).

Quebec is the second-most populous province of Canada, after Ontario. It is the only one to have a predominantly French-speaking population, with French as the sole provincial official language. Most inhabitants live in urban areas near the Saint Lawrence River between Montreal and Quebec City, the capital. Approximately half of Quebec residents live in the Greater Montreal Area, including the Island of Montreal. English-speaking communities and English-language institutions are concentrated in the west of the island of Montreal but are also significantly present in the Outaouais, Eastern Townships, and Gaspé regions. The Nord-du-Québec region, occupying the northern half of the province, is sparsely populated and inhabited primarily by Aboriginal peoples. The climate around the major cities is four-seasons continental with cold and snowy winters combined with warm to hot humid summers, but farther north long winter seasons dominate and as a result the northern areas of the province are marked by tundra conditions. Even in central Quebec, at comparatively southerly latitudes, winters are severe in inland areas.

Quebec independence debates have played a large role in the politics of the province. Parti Québécois governments held referendums on sovereignty in 1980 and 1995. Although neither passed, the 1995 referendum saw the highest voter turnout in Quebec history, at over 93%, and only failed by less than 1%. In 2006, the House of Commons of Canada passed a symbolic motion recognizing the "Québécois as a nation within a united Canada".While the province's substantial natural resources have long been the mainstay of its economy, sectors of the knowledge economy such as aerospace, information and communication technologies, biotechnology, and the pharmaceutical industry also play leading roles. These many industries have all contributed to helping Quebec become an economically influential province within Canada, second only to Ontario in economic output.

Ringed seal

The ringed seal (Pusa hispida or Phoca hispida), also known as the jar seal, as netsik or nattiq by the Inuit and as Ньиэрпэ by the Yakut, is an earless seal (family: Phocidae) inhabiting the Arctic and sub-Arctic regions. The ringed seal is a relatively small seal, rarely greater than 1.5 m in length, with a distinctive patterning of dark spots surrounded by light grey rings, hence its common name. It is the most abundant and wide-ranging ice seal in the Northern Hemisphere: ranging throughout the Arctic Ocean, into the Bering Sea and Okhotsk Sea as far south as the northern coast of Japan in the Pacific, and throughout the North Atlantic coasts of Greenland and Scandinavia as far south as Newfoundland, and include two freshwater subspecies in northern Europe. Ringed seals are one of the primary prey of polar bears and killer whales, and have long been a component of the diet of indigenous people of the Arctic.

Extant Carnivora species

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