Editing Earless seal (section)

==Biology==

===External anatomy===

[[File:Harbor seal with skeleton GS.jpg|thumb|Skeletal anatomy of a harbor seal. 1. Skull. 2. Spine. 3. Tail. 4. Hindlimb. 5. Forelimb. 6. Shoulder. 7. Pelvis. 8. Rib cage.]]
[[File:Phoca vitulina 02 MWNH 1464.JPG|thumb|left|[[Harbor seal]] skull (''Phoca vitulina'')]]

Adult phocids vary from {{convert|1.17|m|ft|abbr=on}} in length and {{convert|45|kg|lb|abbr=on}} in weight in the [[ringed seal]] to {{convert|5.8|m|ft|abbr=on}} and {{convert|4000|kg|lb|abbr=on}} in the [[southern elephant seal]], which is the largest member of the order [[Carnivora]]. Phocids have fewer teeth than land-based members of the [[Carnivora]], although they retain powerful [[canine tooth|canines]]. Some species lack [[Molar (tooth)|molar]]s altogether. The [[dentition|dental formula]] is:
{{DentalFormula|upper=2–3.1.4.0–2|lower=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.<ref name=EoM>{{cite book|editor= Macdonald, D.|author= McLaren, Ian|year= 1984|title= The Encyclopedia of Mammals|publisher= Facts on File|location= New York|pages= [https://archive.org/details/encyclopediaofma00mals_0/page/270 270–275]|isbn= 978-0-87196-871-5|url-access= registration|url= https://archive.org/details/encyclopediaofma00mals_0/page/270}}</ref> 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 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 [[muscle]]s.

[[File:Seal kidney-- FMVZ USP-08.jpg|thumb|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 [[lung]]s during a dive and into the upper respiratory passages, where gases cannot easily be absorbed into the bloodstream. This helps protect the seal from [[Decompression sickness|the bends]]. The [[middle ear]] is also lined with blood sinuses that inflate during diving, helping to maintain a constant pressure.<ref name=EoM/>

Phocids are more specialized for [[Aquatic animal|aquatic]] life than otariids. They lack external ears and have sleek, streamlined bodies. Retractable [[nipple]]s, internal [[testicle]]s,<ref name="PerrinWürsig2009">{{cite book|author1=Perrin, William F. |author2=Würsig, Bernd |author3= Thewissen, J.G.M.|title=Encyclopedia of Marine Mammals|url=https://books.google.com/books?id=2rkHQpToi9sC&q=phocid+OR+phocidae|date=2009|publisher=Academic Press|isbn=978-0-08-091993-5}}</ref> 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.<ref>{{Cite journal|last1=Favilla|first1=Arina B.|last2=Costa|first2=Daniel P.|date=2020-09-11|title=Thermoregulatory Strategies of Diving Air-Breathing Marine Vertebrates: A Review|journal=Frontiers in Ecology and Evolution|volume=8|pages=555509|doi=10.3389/fevo.2020.555509|issn=2296-701X|doi-access=free}}</ref>

===Communication===
Unlike otariids, true seals do not communicate by "barking". Instead, they communicate by slapping the water and grunting. True seals have also been documented to clap at each other underwater.<ref>{{cite web|last1=Hocking|first1=David|last2=Burnville|first2=Ben|last3=Marx|first3=Felix Georg|url=https://www.ncl.ac.uk/press/articles/archive/2020/02/conversationsealsclapping/|title=Comment: Grey seals discovered clapping underwater to communicate|work=[[The Conversation]]|via=[[Newcastle University]]|date=February 3, 2020|accessdate=April 15, 2025}}</ref> One study published in ''[[Animal Behaviour (journal)|Animal Behaviour]]'' found that seals use rhythmic [[percussive]] signalling in both "agonistic interactions" and display behavior.<ref>{{cite journal |last1=Kocsis |first1=Kinga |last2=Duengen |first2=Diandra |last3=Jadoul |first3=Yannick |last4=Ravignani |first4=Andrea |title=Harbour seals use rhythmic percussive signalling in interaction and display |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |date=January 2024 |volume=207 |pages=223–234 |doi=10.1016/j.anbehav.2023.09.014 |bibcode=2024AnBeh.207..223K }}</ref>

===Movements===
With short front flippers and because their rear flipper is unable to rotate, true seals cannot walk when out of the water like sea lions. As a result, they bounce themselves forward in a motion called ''[[wikt:galumphing|galumphing]]'';<ref>{{cite book|last=Dipper|first=Frances|title=[[Royal Society for the Protection of Birds|RSPB]] Spotlight: Seals|page=20|publisher=[[Bloomsbury Publishing|Bloomsbury Wildlife]]|location=[[London]]|isbn=978-1-4214-0305-2|date=2021}}</ref><ref>{{cite book|last=Derocher|first=Andrew E.|title=Polar Bears: A Complete Guide to Their Biology and Behavior|page=73|publisher=[[Johns Hopkins University Press]]|location=[[Baltimore]]|isbn=978-1-4214-0305-2|date=2012}}</ref> the polar explorer [[Edward Wilson (explorer)|Edward Wilson]] referred to the motion as ''lolloping''.<ref>{{cite book|last=Schmidt|first=Jeremy|title=Weddell Seals: Science, Life History, and Population Dynamics|page=59|publisher=Weddell Seal Science|isbn=978-1-881480-19-8|date=2023}}</ref>

===Reproduction===
[[File:Earless seal (Puerto Madryn, Argentina).jpg|thumb|left|Southern elephant seals in Argentina|alt=Photo of seven adult and juvenile southern elephant seals packed closely on beach]]
[[File:Pusa hispida saimensis ca 1956.jpg|thumb|Living only in [[Lake Saimaa]], [[Finland]], [[Saimaa ringed seal]]s, a subspecies of [[ringed seal]], are among the most [[Endangered species|endangered]] seals in the world, having a total population of only about 400 individuals.<ref>{{cite web |title= Saimaa Ringed Seal |url= https://wwf.fi/en/saimaaringedseal/  |access-date=22 December 2018}}</ref>]]
<!--[[File:Zwei junge Seehunde am Strand.jpg|thumb|[[Paul de Vos]]:Two young seals on a beach]]-->

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 [[Eared seal|otariids]], in which the mother makes short foraging trips between nursing bouts.{{fact|date=April 2025}}

Because a phocid mother's feeding grounds are often hundreds of kilometers from the breeding site, she must [[fasting|fast]] while [[lactation|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 whale]]s' strategy, which involves fasting during their months-long migration from arctic feeding areas to tropical breeding/nursing areas and back.{{fact|date=April 2025}}

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.{{fact|date=April 2025}}

===Growth and maturation===

The pup's diet is so high in [[Calorie|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 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.<ref>{{Cite journal|title = The energetics of lactation in the Northern elephant seal, ''Mirounga angustirostris''|journal = Journal of Zoology|date = 1986|pages = 21–33|volume = 209|issue = 1|doi = 10.1111/j.1469-7998.1986.tb03563.x|first1 = D. P.|last1 = Costa|first2 = B. J. Le|last2 = Boeuf|first3 = A. C.|last3 = Huntley|first4 = C. L.|last4 = Ortiz}}</ref> 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.

=== Feeding strategy ===

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 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.<ref>{{Cite journal|last1=Kienle|first1=Sarah S.|last2=Berta|first2=Annalisa|date=2016|title=The better to eat you with: the comparative feeding morphology of phocid seals (Pinnipedia, Phocidae)|journal=Journal of Anatomy|volume=228|issue=3|pages=396–413|doi=10.1111/joa.12410|pmc=5341551|pmid=26646351}}</ref>