Earless seal

{{Short description|Family of mammals}} {{distinguish|text=Phocides, a genus of butterflies, Pholcidae, a family of spiders, or Phocoenidae, a family of delphinodea}} {{Automatic taxobox | name = Earless seals<ref name=msw3>{{MSW3 Wozencraft | pages = | id = 14001028}}</ref> | image = Seehund.jpg | image_caption = Harbor seal, ''Phoca vitulina'' | fossil_range = {{Fossil range|earliest=Chattian|Aquitanian|present}}Early Miocene – Holocene, possible late Oligocene record<ref name=Noriphoca>{{Cite journal|author1=Leonard Dewaele |author2=Olivier Lambert |author3=Stephen Louwye |year=2018 |title=A critical revision of the fossil record, stratigraphy and diversity of the Neogene seal genus ''Monotherium'' (Carnivora, Phocidae) |journal=Royal Society Open Science |volume=5 |issue=5 |article-number=171669 |doi=10.1098/rsos.171669 |doi-access=free|pmid=29892365 |pmc=5990722 |bibcode=2018RSOS....571669D }}</ref> | taxon = Phocidae | display_parents = 2 | authority = Gray, 1821 | type_genus = ''Phoca'' | type_genus_authority = Linnaeus, 1758 | subdivision_ranks = Subfamilies | subdivision = *†Devinophocinae *Monachinae *Phocinae | range_map = File:Phocidae distribution.png | range_map_caption = Phocidae distribution }}

The '''earless seals''', also known as '''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''' ({{IPAc-en|ˈ|f|oʊ|s|ᵻ|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 is the only species of exclusively freshwater seal.

==Taxonomy and evolution==

===Evolution=== [[File:Cranio Pliophoca etrusca, Orciano.JPG|thumb|Fossil ''Pliophoca'' skull]]

The earliest known fossil earless seal is ''Noriphoca gaudini'' from the late Oligocene or earliest Miocene (Aquitanian) of Italy.<ref name=Noriphoca /> Other early fossil phocids date from the mid-Miocene, 15 million years ago in the north Atlantic.<ref name=Noriphoca /><ref>{{Cite journal|last1=Dewaele|first1=Leonard|last2=Lambert|first2=Olivier|last3=Louwye|first3=Stephen|date=2017-02-21|title=On ''Prophoca'' and ''Leptophoca'' (Pinnipedia, Phocidae) from the Miocene of the North Atlantic realm: redescription, phylogenetic affinities and paleobiogeographic implications|journal=PeerJ|language=en|volume=5|article-number=e3024|doi=10.7717/peerj.3024|pmid=28243538|doi-access=free|pmc=5322758}}</ref> 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 mustelids and bears.<ref>{{Cite journal|last1=Paterson|first1=Ryan S.|last2=Rybczynski|first2=Natalia|last3=Kohno|first3=Naoki|last4=Maddin|first4=Hillary C.|date=2020|title=A Total Evidence Phylogenetic Analysis of Pinniped Phylogeny and the Possibility of Parallel Evolution Within a Monophyletic Framework|journal=Frontiers in Ecology and Evolution|language=en|volume=7|article-number=457 |doi=10.3389/fevo.2019.00457|doi-access=free |bibcode=2020FrEEv...7..457P }}</ref>

Monk seals and elephant seals were previously believed to have first entered the Pacific through the open straits between North and South America,<ref name="Fulton-2010" /> with the Antarctic true seals either using the same route or travelled down the west coast of Africa.<ref>{{cite book |author1=Savage, RJG |author2= Long, MR |name-list-style=amp|year=1986 |title= Mammal Evolution: an illustrated guide|url=https://archive.org/details/mammalevolutioni0000sava |url-access=registration |publisher= Facts on File|location=New York|pages= [https://archive.org/details/mammalevolutioni0000sava/page/94 94–95]|isbn= 978-0-8160-1194-0}}</ref> It 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.<ref>{{Cite journal|last1=Rule|first1=James P.|last2=Adams|first2=Justin W.|last3=Marx|first3=Felix G.|last4=Evans|first4=Alistair R.|last5=Tennyson|first5=Alan J. D.|last6=Scofield|first6=R. Paul|last7=Fitzgerald|first7=Erich M. G.|date=2020-11-11|title=First monk seal from the Southern Hemisphere rewrites the evolutionary history of true seals|journal=Proceedings of the Royal Society B: Biological Sciences|volume=287|issue=1938|article-number=20202318|doi=10.1098/rspb.2020.2318|pmid=33171079|pmc=7735288|doi-access=free}}</ref>

===Taxonomy===

{{Cladogram|align=left|title= |clade= {{clade |style=font-size:75%;line-height:75%;width:500px; |label1=Pinnipedia |1={{clade |label1='''Phocidae''' |1={{clade |label1=Phocinae |1={{clade |1=Bearded seal |2={{clade |1=Hooded seal |label2=Phocini |2={{clade |1={{clade |1={{clade |1={{clade |1={{clade |1=Ringed seal |2=Baikal seal }} |2=Caspian seal }} |2={{clade |1=Spotted seal |2=Harbor seal }} }} |2=Grey seal }} |2={{clade |1=Ribbon seal |2=Harp seal }} }} }} }} |label2=Monachinae |2={{clade |1={{clade |label1=Lobodontini |1={{clade |1={{clade |1={{clade |1=Weddell seal |2=Leopard seal }} |2=Crabeater seal }} |2=Ross seal }} |label2=Miroungini|sublabel2=(elephant seals) |2={{clade |1=Southern elephant seal |2=Northern elephant seal }} }} |label2=Monachini |2={{clade |1=Mediterranean monk seal |2=Hawaiian monk seal |3=Caribbean monk seal }} }} }} |2={{clade |1=Otariidae (eared seals) |2=Odobenidae (Walrus) }} }} }} |caption=Cladogram showing relationships among the phocids, combining several phylogenetic analyses.<ref name="Berta Churchill Boessenecker 2018">{{cite journal | last1=Berta | first1=Annalisa | last2=Churchill | first2=Morgan | last3=Boessenecker | first3=Robert W. | title=The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses | journal=Annual Review of Earth and Planetary Sciences | publisher=Annual Reviews | volume=46 | issue=1 | date=2018-05-30 | issn=0084-6597 | doi=10.1146/annurev-earth-082517-010009 | pages=203–228| bibcode=2018AREPS..46..203B | s2cid=135439365 | doi-access=free }}</ref> }}

In 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).<ref>{{Cite journal|last1=Árnason|first1=Úlfur|last2=Bodin|first2=Kristina|last3=Gullberg|first3=Anette|last4=Ledje|first4=Christina|last5=Suzette|first5=Mouchaty|date=1995|title=A molecular view of pinniped relationships with particular emphasis on the true seals|journal=Journal of Molecular Evolution|volume=40 |issue=1 |pages=78–85|doi=10.1007/BF00166598|pmid=7714914 |bibcode=1995JMolE..40...78A |s2cid=7537924}}</ref><ref>{{Cite journal|last1=Arnason |first1=Ulfur |last2=Gullberg |first2=Anette |last3=Janke|first3=Axel |last4=Kullberg|first4=Morgan |last5=Lehman |first5=Niles |last6=Petrov |first6=Evgeny A.|last7=Väinölä|first7=Risto|date=2006-11-01 |title=Pinniped phylogeny and a new hypothesis for their origin and dispersal|journal=Molecular Phylogenetics and Evolution |volume=41|issue=2 |pages=345–354|doi=10.1016/j.ympev.2006.05.022 |pmid=16815048|bibcode=2006MolPE..41..345A }}</ref><ref>{{Cite journal|last1=Fulton|first1=Tara Lynn|last2=Strobeck|first2=Curtis |date=2010|title=Multiple markers and multiple individuals refine true seal phylogeny and bring molecules and morphology back in line |journal=Proceedings of the Royal Society B: Biological Sciences |volume=277 |issue=1684 |pages=1065–1070 |doi=10.1098/rspb.2009.1783|pmc=2842760|pmid=19939841 |bibcode=2010PBioS.277.1065F }}</ref><ref name="Fulton-2010">{{Cite journal |last1=Fulton |first1=Tara L. |last2=Strobeck|first2=Curtis |date=2010|title=Multiple fossil calibrations, nuclear loci and mitochondrial genomes provide new insight into biogeography and divergence timing for true seals (Phocidae, Pinnipedia) |journal=Journal of Biogeography |volume=37|issue=5 |pages=814–829 |doi=10.1111/j.1365-2699.2010.02271.x|bibcode=2010JBiog..37..814F |s2cid=59436229 }}</ref> 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 the tribe Lobodontini. Tribe Miroungini is composed of the elephant seals. The Monk seals (''Monachus'' and ''Neomonachus'') are all part of the tribe Monachini.<ref>{{Cite journal |last1=Scheel |first1=Dirk-Martin|last2=Slater|first2=Graham J.|last3=Kolokotronis|first3=Sergios-Orestis |last4=Potter |first4=Charles W.|last5=Rotstein|first5=David S.|last6=Tsangaras|first6=Kyriakos |last7=Greenwood|first7=Alex D.|last8=Helgen|first8=Kristofer M.|date=2014|title=Biogeography and taxonomy of extinct and endangered monk seals illuminated by ancient DNA and skull morphology |journal=ZooKeys|issue=409 |pages=1–33|doi=10.3897/zookeys.409.6244|pmc=4042687|pmid=24899841|doi-access=free|bibcode=2014ZooK..409....1S }}</ref> 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.<ref>{{Cite journal|last1=Berta|first1=Annalisa |last2=Churchill|first2=Morgan|date=2012 |title=Pinniped taxonomy: review of currently recognized species and subspecies, and evidence used for their description|journal=Mammal Review |volume=42 |issue=3|pages=207–234 |doi=10.1111/j.1365-2907.2011.00193.x|bibcode=2012MamRv..42..207B }}</ref>

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.<ref name="Bonner1994">{{cite book | last1 = Bonner | first1 = N. | year = 1994| title = Seals and Sea Lions of the World | publisher = Blandford |location= United Kingdom | pages = 1–224 |isbn = 978-0-8160-5717-7}}</ref> {{Clear}}

===Extant genera=== {| class="wikitable" |- ! Subfamily!! Tribe !! Image !! Genus !! species |- ! rowspan="7" style="text-align:center;"| Subfamily Monachinae ! rowspan="2" style="text-align:center;"| Tribe Monachini |175px ||''Monachus'' Fleming, 1822 || * Mediterranean monk seal, ''Monachus monachus'' |- |175px ||''Neomonachus'' Slater & Helgen, 2014 || *Hawaiian monk seal, ''Neomonachus schauinslandi'' |- ! rowspan="1" style="text-align:center;"| Tribe Miroungini |175px ||''Mirounga'' Gray, 1827 || * Northern elephant seal, ''Mirounga angustirostris'' * Southern elephant seal, ''Mirounga leonina'' |- ! rowspan="4" style="text-align:center;"| Tribe Lobodontini |175px ||''Ommatophoca'' Gray, 1844 || * Ross seal, ''Ommatophoca rossi'' |- |175px ||''Lobodon'' Gray, 1844 || * Crabeater seal, ''Lobodon carcinophagus'' |- |175px ||''Hydrurga'' Gistel, 1848 || * Leopard seal, ''Hydrurga leptonyx'' |- |175px ||''Leptonychotes'' Gill, 1872 || * Weddell seal, ''Leptonychotes weddellii'' |- ! rowspan="7" style="text-align:center;"| Subfamily Phocinae ! rowspan="1" style="text-align:center;"| Tribe Cystophorini |175px ||''Cystophora'' Nilsson, 1820 || * Hooded seal, ''Cystophora cristata'' |- ! rowspan="1" style="text-align:center;"| Tribe Erignathini |175px ||''Erignathus'' Gill, 1866 || * Bearded seal, ''Erignathus barbatus'' |- ! rowspan="5" style="text-align:center;"| Tribe Phocini |175px ||''Phoca'' Linnaeus, 1758 || * Harbor seal or common seal, ''Phoca vitulina'' * Spotted seal, ''Phoca largha'' |- |175px ||''Pusa'' Scopoli, 1771 || * Ringed seal, ''Pusa hispida'' (formerly ''Phoca hispida'') * Baikal seal, ''Pusa sibirica'' (formerly ''Phoca sibirica'') * Caspian seal, ''Pusa caspica'' (formerly ''Phoca caspica'') * Saimaa ringed seal, ''Pusa saimensis'' (formerly ''Pusa hispida saimensis'') |- |175px ||''Pagophilus'' Gray, 1844 || * Harp seal, ''Pagophilus groenlandicus'' (formerly ''Phoca groenlandica'') |- |175px ||''Histriophoca'' Gill, 1873 || * Ribbon seal, ''Histriophoca fasciata'' (formerly ''Phoca fasciata'') |- |175px ||''Halichoerus'' Nilsson, 1820 || * Grey seal, ''Halichoerus grypus'' |- |}

==Biology==

===External anatomy===

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, the largest member of 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: {{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 in a sideways motion with their bodies;<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 primarily used for steering, whereas their hind flippers are used for underwater propulsion.<ref>{{Cite web |title=Harbor Seal (Phoca vitulina) |url=https://www.adfg.alaska.gov/index.cfm?adfg=harborseal.printerfriendly |access-date=2026-02-06 |website=www.adfg.alaska.gov}}</ref> While phocids' streamlined bodies make them better long-distance swimmers than otariids, unlike fur seals, their hind flippers are bound to the pelvis and unable to be rotated forward for walking. As a result, they are clumsy on land, having to wriggle with their front flippers and abdominal muscles.

thumb|Seal kidney

Phocid respiratory and circulatory systems are adapted to facilitate diving into considerable depths, allowing them to spend long periods of time underwater. When a seal dives, air is forced from the lungs and into the upper respiratory passages, where gases cannot easily be absorbed into the bloodstream, protecting it from the bends. The middle ear is also lined with blood sinuses that inflate during diving, helping to maintain a constant pressure.<ref name=EoM/>

Phocid bodies are more specialized for aquatic life than otariids, as supported by the presence of ear holes (as opposed to external ears in fur seals), retractable nipples, internal testicles,<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. Phocids are able to divert blood flow to a smooth layer of blubber underneath their skin to help regulate body temperature.<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|article-number=555509|doi=10.3389/fevo.2020.555509|issn=2296-701X|doi-access=free |bibcode=2020FrEEv...855509F }}</ref>

===Communication=== Unlike otariids, phocine seals do not communicate by "barking". Instead, they communicate by slapping the water and grunting, with a few species having 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|access-date=April 15, 2025}}</ref> One study published in ''Animal Behaviour'' found that seals use rhythmic percussive signalling (clapping) 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 |date=January 2024 |volume=207 |pages=223–234 |doi=10.1016/j.anbehav.2023.09.014 |bibcode=2024AnBeh.207..223K |url=https://pure.au.dk/portal/en/publications/71a58fc8-a077-4711-a11f-232490706e71 }}</ref>

Conversely, monachine seals are well known to vocalize: Elephant seals often vocalize on land,{{Clarify|reason=What do the females and pups sound like?|date=July 2025}} with the bulls being well known for roaring to establish dominance and identify themselves.<ref name="McCann 1981">{{cite journal |first=T. S. |last= McCann |year=1981 |title=Aggression and sexual activity of male Southern elephant seals, ''Mirounga leonina'' |journal=Journal of Zoology |volume=195 |issue=3 |pages=295–310 |doi=10.1111/j.1469-7998.1981.tb03467.x}}</ref> The Weddell and leopard seals are well known for their underwater singing.<ref>{{Cite journal|last=Terhune|first=John M.|date=2017-04-13|title=Through-ice communication by Weddell seals (Leptonychotes weddellii) is possible|journal=Polar Biology|volume=40|issue=10|pages=2133–2136|doi=10.1007/s00300-017-2124-1|bibcode=2017PoBio..40.2133T |s2cid=23069267|issn=0722-4060}}</ref><ref>{{Cite journal|last1=Green|first1=K.|last2=Burton|first2=H. R.|date=January 1988|title=Do Weddell seals sing?|journal=Polar Biology|volume=8|issue=3|pages=165–166|doi=10.1007/bf00443448|bibcode=1988PoBio...8..165G |s2cid=46256980|issn=0722-4060}}</ref><ref>{{cite journal|author= Rogers TL |year=2014|title= Source levels of the underwater calls of a male leopard seal |journal= The Journal of the Acoustical Society of America|volume=136|issue=4|pages= 1495–1498|doi=10.1121/1.4895685|pmid=25324053|bibcode=2014ASAJ..136.1495R}}</ref><ref>{{Cite journal|last1=Rogers|first1=Tracey L.|last2=Cato|first2=Douglas H.|date=2002|title=Individual Variation in the Acoustic Behaviour of the Adult Male Leopard Seal, Hydrurga leptonyx|jstor=4535987|journal=Behaviour|volume=139|issue=10|pages=1267–1286|doi=10.1163/156853902321104154 |bibcode=2002Behav.139.1267R }}</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 ''galumphing'';<ref>{{cite book|last=Dipper|first=Frances|title=RSPB Spotlight: Seals|page=20|publisher=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 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> It is also referred to as "worm-style" locomotion.<ref>{{Cite journal |last1=Esteban |first1=Juan Miguel |last2=Martín-Serra |first2=Alberto |last3=Pérez-Ramos |first3=Alejandro |last4=Rybczynski |first4=Natalia |last5=Pastor |first5=Francisco J. |last6=Figueirido |first6=Borja |date=2023 |title=Investigating the land-to-sea transition in carnivorans from the evolution of sacrum morphology in pinnipeds |url=https://link.springer.com/10.1007/s10914-023-09650-y |journal=Journal of Mammalian Evolution |language=en |volume=30 |issue=2 |pages=341–362 |doi=10.1007/s10914-023-09650-y |issn=1064-7554|hdl=10630/26300 |hdl-access=free }}</ref>

===Reproduction=== thumb|left|Southern elephant seals in Argentina|alt=Photo of seven adult and juvenile southern elephant seals packed closely on beach [[File:Antarctica_2013_Journey_to_the_Crystal_Desert_(8369569335).jpg|thumb|Weddell Seal in Antarctica]] [[File:Pusa hispida saimensis ca 1956.jpg|thumb|Living only in Lake Saimaa, Finland, Saimaa ringed seals, a subspecies of ringed seal, are among the most 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>]]

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<ref>{{Cite journal |last1=Sauvé |first1=Caroline C. |last2=Van de Walle |first2=Joanie |last3=Hammill |first3=Mike O. |last4=Arnould |first4=John P. Y. |last5=Beauplet |first5=Gwénaël |date=2014 |title=Stomach temperature records reveal nursing behaviour and transition to solid food consumption in an unweaned mammal, the harbour seal pup (Phoca vitulina) |journal=PLOS ONE |volume=9 |issue=2 |article-number=e90329 |doi=10.1371/journal.pone.0090329 |doi-access=free |issn=1932-6203 |pmc=3936010 |pmid=24587327 |bibcode=2014PLoSO...990329S }}</ref><ref>{{Cite web |date=2023-10-30 |title=Grey seal pup season {{!}} Cumbria Wildlife Trust |url=https://www.cumbriawildlifetrust.org.uk/blog/grey-seal-pup-season |access-date=2026-04-24 |website=www.cumbriawildlifetrust.org.uk |language=en}}</ref>. 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.{{citation needed|date=April 2025}}

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.{{citation needed|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). Phocids are known to deliberately nurse young that are not their own, this is particularly seen in individuals that have lost their own pup<ref>{{Cite journal |last1=Arso Civil |first1=Mònica |last2=Hague |first2=Emily |last3=Langley |first3=Izzy |last4=Scott-Hayward |first4=Lindesay |date=2021-08-17 |title=Allo-suckling occurrence and its effect on lactation and nursing duration in harbour seals (Phoca vitulina) in Orkney, Scotland |journal=Behavioral Ecology and Sociobiology |language=en |volume=75 |issue=8 |page=121 |doi=10.1007/s00265-021-03051-y |bibcode=2021BEcoS..75..121A |issn=1432-0762|hdl=10023/23793 |hdl-access=free }}</ref>."Milk stealers" that suckle from unrelated, sleeping females are not uncommon; this often results in the death of the mother's own pup through starvation<ref>{{Cite journal |last1=Baker |first1=J. R. |last2=Jepson |first2=P. D. |last3=Simpson |first3=V. R. |last4=Kuiken |first4=T. |date=1998-05-30 |title=Causes of mortality and non-fatal conditions among grey seals (Halichoerus grypus) found dead on the coasts of England, Wales and the Isle of Man |journal=The Veterinary Record |volume=142 |issue=22 |pages=595–601 |doi=10.1136/vr.142.22.595 |issn=0042-4900 |pmid=9682418}}</ref><ref>{{Cite journal |last1=Steiger |first1=G. H. |last2=Calambokidis |first2=J. |last3=Cubbage |first3=J. C. |last4=Skilling |first4=D. E. |last5=Smith |first5=A. W. |last6=Gribble |first6=D. H. |date=July 1989 |title=Mortality of harbor seal pups at different sites in the inland waters of Washington |journal=Journal of Wildlife Diseases |volume=25 |issue=3 |pages=319–328 |doi=10.7589/0090-3558-25.3.319 |issn=0090-3558 |pmid=2761005 |bibcode=1989JWDis..25..319S }}</ref>; another side-effect of milk stealing in some species of phocid is the formation of "super weaners"<ref>{{Cite web |date=2015-01-12 |title=Science Word of the Day: Super-weaner |url=https://www.nationalgeographic.com/science/article/science-word-of-the-day-super-weaner |access-date=2026-04-24 |website=Science |language=en}}</ref>.

===Growth and maturation===

The pup's diet is so high in food energy 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>

==See also== * Marine mammals as food

==References== {{Reflist}}

{{Portal-bar|Mammals|Animals|Marine life}} {{Carnivora|C1.}} {{Pan-Pinnipedia|P.|state=autocollapse}} {{Taxonbar|from=Q25587}} {{Authority control}}

Category:Extant Miocene first appearances Category:Pinnipeds Category:Taxa named by John Edward Gray Category:Non-human celestial navigation Category:Taxa described in 1821 Category:Earless seals