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''Phoca'' ( ) is a genus of the
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 th ...
s, within the family Phocidae. It now contains just two species, the
common seal The harbor (or harbour) seal (''Phoca vitulina''), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared sea ...
(or harbour seal) and the
spotted seal The spotted seal (''Phoca largha''), also known as the larga seal or largha seal, is a member of the family Phocidae, and is considered a "true seal". It inhabits ice floes and waters of the north Pacific Ocean and adjacent seas. It is primaril ...
(or largha seal). Several species formerly listed under this genus have been split into the genera ''
Pusa ''Pusa'' is a genus of the earless seals, within the family Phocidae. The three species of this genus were split from the genus '' Phoca'', and some sources still give ''Phoca'' as an acceptable synonym for ''Pusa''. The three species in this ...
'', '' Pagophilus'', and '' Histriophoca''. Until recently, ''Phoca largha'' has been considered a subspecies of ''Phoca vitulina'' but now is considered its own species. For this reason, the fossil history of the genus is unclear, and it has formerly been used as
wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the purpose of classifying organisms that do not fit anywhere else. They are typically defined by e ...
for a number of fossils of uncertain affinity.


Species

Currently there are two confirmed members: There is also a third unconfirmed member: Former members of ''Phoca'': * ''Histriophoca fasciata'' (
ribbon seal The ribbon seal (''Histriophoca fasciata'') is a medium-sized pinniped from the true seal family (Phocidae). A seasonally ice-bound species, it is found in the Arctic and Subarctic regions of the North Pacific Ocean, notably in the Bering Sea and ...
) * ''Pusa caspica'' (
Caspian seal The Caspian seal (''Pusa caspica'', syn. ''Phoca 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. It lives along the shorelines, but also on the many ro ...
) * ''Pusa hispida'' ( ringed seal) * ''Pusa sibirica'' (nerpa or
Baikal seal The Baikal seal (''Pusa sibirica''), also known as Lake Baikal seal or Baikal nerpa (), is a species of earless seal endemic to Lake Baikal in Siberia, Russia. The Baikal seal is one of the smallest earless/true seals, and the only exclusively ...
) * ''Pagophilus groenlandica'' (
harp seal The harp seal (''Pagophilus groenlandicus''), also known as the saddleback seal or Greenland seal, 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 ...
)


Mating ecology

Both harbour and spotted seals are aquatically mating
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant taxon, extant families Odobenidae (whose onl ...
s. Mating occurs in the water around the time when pups are weaned. Females in
estrus The estrous cycle (, originally ) is a set of recurring physiological changes induced by reproductive hormones in females of mammalian subclass Theria. Estrous cycles start after sexual maturity in females and are interrupted by anestrous phas ...
are typically more dispersed than land-breeding pinnipeds and the distinction between foraging and reproductive behavior is less apparent. For this reason, it is difficult to study the mating patterns of this genus. Female harbour seals start making foraging trips shortly before weaning their pup and consequently are widely dispersed when in estrus. Males restrict their range around the time females start to make these foraging trips. Harbour seals follow a
polygynous Polygyny () is a form of polygamy entailing the marriage of a man to several women. The term polygyny is from Neoclassical Greek πολυγυνία (); . Incidence Polygyny is more widespread in Africa than in any other continent. Some scholar ...
mating system. More specifically it has been shown that male harbour seals partake in lek polygyny. Male seals defend underwater territories with well-defined boundaries. The most valuable territories are near haulouts or along traffic corridors that provide maximum exposure to estrous females. One male will occupy an area throughout the breeding season, and they will return to the same display area in consecutive years. Female harbour seals receive direct benefits from being in a lek, as the congregation of males into an area makes
mate selection Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior.Bateson, Paul Patrick Gordon. "Mate Choice." Mate Choi ...
easier because females do not have to travel as far and it also helps to reduce exposure to predators. Harbour seal males use underwater vocalizations and display dives within their aquatic territories, for both female attraction and male-male competition. Male harbour seal vocalizations consist of low-frequency broadband growls that peak in occurrence during the mating season. Males vocalize and display in small, distinct territories covering around 40–135 m2. Each display area is spatially discrete and can be separated by up to 250 meters. Male harbour seals have considerable individual and geographic variation in their underwater vocalizations. Territory holders use the acoustic displays of intruders to locate and challenge invaders and will respond aggressively to a male call. Males assess each other by their vocalizations before deciding whether to respond.Nicholson, T. E. (2000). Social structure and underwater behavior of harbor seals in southern Monterey Bay, California. M.S. thesis, San Francisco State University. These vocalizations are energetically expensive to produce and are honest signals of male quality and dominance. Male body condition will decline as the mating season progresses. Aquatic hierarchies in harbour seals develop before the breeding season and dominance is determined by direct male contests. These contests involve repeated confrontations between two males using surface splashing, fighting, paired somersaulting, and chasing techniques. The hierarchies may aid in holding territories or to
mate Mate may refer to: Science * Mate, one of a pair of animals involved in: ** Mate choice, intersexual selection *** Mate choice in humans ** Mating * Multi-antimicrobial extrusion protein, or MATE, an efflux transporter family of proteins Pers ...
with females during the breeding season. The dominance relationships are determined by size and sex, with adult males dominant to sub-adult males, and sub-adult females submissive to all other social classes. Aquatic courtship is long in duration and involves rolling, bubble blowing, and splashing to attract females. Female choice appears to play a strong role in this
mating system A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to animals, the term describes which males and females mating, mate under which circumstances. Reco ...
but it has yet to be formally studied. The mating system of spotted seals is quite different from harbour seals as spotted seals are serially monogamous. During the
breeding season Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ...
, a male will join a female approximately ten days before the female gives birth to a pup from the previous years mating. The pairs are considered to be territorial as they keep widely spaced from other spotted seals. The social group consists of an isolated adult pair and the females pup. The female spotted seal receives direct benefits from the male as he provides protection for her and the pup until it is weaned. Immediately after weaning mating occurs.


References

{{Authority control Phocins Carnivoran genera Taxa named by Carl Linnaeus