Editing Pinniped (section)

===Reproductive behavior===
[[File:Phoca vitulina vitulina 201906 45.jpg|thumb|Harbor seals on sandy beach. This species breeds on land but mates in the water.{{sfn|Riedman|1990|p=212}}]]
The [[mating system]] of pinnipeds varies from extreme polygyny to [[serial monogamy]].{{sfn|Riedman|1990|pp=180–183}}  Species that breed on land are usually more polygynous, as females gather in large aggregations and males are able to mate with them as well as defend them from rivals. These species include elephant seals, [[grey seal]]s and most otariids.<ref name=dimorphism/> Land-breeding pinnipeds prefer to mate on islands where there are fewer land predators. Suitable islands are in short supply and tend to be crowded. Since the land they breed on is fixed, females return to the same sites for many years. The males arrive earlier in the season and wait for them. The males stay on land to monopolize females; and may fast for months as they would lose their position if they went to feed at sea.{{sfn|Riedman|1990|pp=178–179}} Polygynous species also tend to be extremely sexual dimorphic in favor of males. This dimorphism manifests itself in larger chests and necks, longer canines and denser fur—all traits that equip males for combat. Larger males have more blubber and thus more energy reserves for fasting.<ref name=dimorphism/>

Other seals, like the walrus and most phocids, [[Ice seal|breed on ice]] and [[Copulation (zoology)|copulate]] in the water—a few land-breeding species also mate in water.<ref name=dimorphism/>{{sfn|Riedman|1990|p=212}} Females of these species tend to be more spaced out and there is less [[Philopatry|site fidelity]], since ice is less stable than solid land. Hence polygyny tends to be weaker in ice-breeding species. An exception to this is the walrus, whose distribution of food forces females closer together. Pinnipeds that breed on fast ice tend to cluster together more than those that breed on drift ice.{{sfn|Riedman|1990|pp=184–188, 196}} Seals that breed on ice tend to have little or no sexual dimorphism. In Antarctic seals, there is some size bias in favor of females. Walruses and [[hooded seal]]s are unique among ice-breeding species in that they have pronounced sexual dimorphism in favor of males.<ref name=dimorphism/>{{sfn|Riedman|1990|pp=187–188}}
[[File:Callorhinus ursinus and harem.jpg|thumb|left|Northern fur seal breeding colony]]
Adult male pinnipeds have several strategies to ensure [[reproductive success]]. Otariid males gain access to females by establishing [[Territory (animal)|territories]] where females can bask and give birth and contain valuable resources such as shade, tide pools or access to water. Territories are usually marked by natural barriers,<ref name=mating>Mesnick, S. L.; Ralls, K. "Mating systems" in {{harvnb|Perrin|Würsig|Thewissen|2009|pp=712–718}}</ref> and some may be fully or partially underwater.<ref>Odell, D. K. "The Fight to Mate: Breeding strategy of California sea lions" in {{harvnb|MacDonald|2001|pp=172–173}}</ref> Males defend their territorial boundaries with threatening vocalizations and postures, but physical fights are usually not very violent, and are mostly limited to early in the season.<ref name=aggressive>Campagna, C. "Aggressive behavior, intraspecific" in {{harvnb|Perrin|Würsig|Thewissen|2009|pp=18–22}}</ref> Individuals also return to the same territorial site each breeding season. In certain species, like the Steller sea lion and northern fur seal, a dominant male can maintain a territory for as long as 2–3 months. Females can usually move freely between territories and males are unable to coerce females who are intent on leaving, but in some species such as the northern fur seal, South American sea lion and Australian sea lion, males keep females in their territories with threatening displays and even violence. In some phocid species, like the harbor seal, Weddell seal and bearded seal, the males establish "maritories" and patrol and defend the waters bordering female haul-out areas, waiting for a female to enter.<ref name=mating/> These are also maintained by vocalizations.<ref name=communication/> The maritories of Weddell seal males include entries to female breathing holes in the ice.{{sfn|Riedman|1990|p=186}}
[[File:Northern elephant seals fighting.webm|thumb|right|Male northern elephant seals fighting for dominance and females]]
[[Lek mating|Lek systems]] are known to exist among some populations of walruses.<ref name=mating/> These males gather near female herds and try to attract them with elaborate [[courtship display]]s and vocalizations.<ref name=mating/>{{sfn|Riedman|1990|pp=212–215}} Lekking may also exist among California sea lions, South American fur seals, New Zealand sea lions and harbor seals.<ref name=mating/><ref>{{cite journal|author1=Boness, D. J. |author2=Bowen, D. |author3=Buhleier, B. M. |author4=Marshall, G. J. |year=2006 |title=Mating tactics and mating system of an aquatic-mating pinniped: the harbor seal, ''Phoca vitulina'' |journal=Behavioral Ecology and Sociobiology |volume=61 |pages=119–30 |doi=10.1007/s00265-006-0242-9 |s2cid=25266746 |url=https://www.researchgate.net/publication/226692255}}</ref> In some species, including elephant seals, grey seals and non-lekking walruses, males will try to lay claim to the desired females and defend them from rivals. Elephant seal males, in particular, establish [[dominance hierarchies]] via displays and fights, with the highest ranking males having a near monopoly on reproductive success.<ref name=mating/> An alpha male can have a [[harem (zoology)|harem]] of 100 females.<ref>{{cite journal |vauthors=Leboeuf BJ |title=Sexual behavior in the Northern Elephant seal ''Mirounga angustirostris'' |journal=Behaviour |volume=41 |issue=1 |pages=1–26 |year=1972 |pmid=5062032 |doi=10.1163/156853972X00167 |jstor=4533425 }}</ref> Grey seal males usually place themselves among a cluster of females whose members may change over time,<ref name="Lidgard">{{cite journal|author1=Lidgard, D. C. |author2=Boness, D. J. |author3=Bowen, W. D. |author4=McMillan, J. I. |year=2005|title=State-dependent male mating tactics in the grey seal: the importance of body size|journal=Behavioral Ecology|volume=16|issue=3|pages=541–49|doi=10.1093/beheco/ari023}}</ref> while males of some walrus populations guard female herds.<ref name=mating/> Male ringed, crabeater, spotted and hooded seals follow and defend nearby females and mate with them when they reach estrus. These may be lone females or small groups.{{sfn|Riedman|1990|p=196}}<ref name=mating/> South American sea lions are considered to be both a territory-defending and female-defending species.<ref name=mating/> Males start the season establishing and defending territories but then claim and defend females when they arrive.<ref>{{cite journal|author=Campagna, C., B. Le Boeuf|year=1988|title=Reproductive behavior of southern sea lions|journal=Behaviour|volume=104|issue=3–4|pages=233–261|doi=10.1163/156853988X00539|jstor=4534669}}</ref>

Younger or subdominant male pinnipeds may attempt to [[Alternative mating strategy|achieve reproductive success in other ways]] including sneakiness, harassment of females or even coordinated disruption of the colony. Female pinnipeds do appear to have some choice in mates, particularly in lek-breeding species like the walrus, but also in elephant seals where the males try to dominate all the females that they want to mate with.{{sfn|Riedman|1990|pp=209–210, 212–215}} When a female elephant seal or grey seal is mounted by an unwanted male, she tries to resist and get away. This commotion attracts other males to the scene, and the most dominant will take over and mate with female himself.<ref>{{cite journal |author1=Cox, C. R. |author2=Le Boeuf, B. J. |year=1977 |title=Female incitation of male competition: A mechanism in sexual selection |journal=The American Naturalist |volume=111 |issue=978 |pages=317–35 |jstor=2460066 |doi=10.1086/283163|s2cid=84788148 }}</ref><ref>{{cite journal |author1=Boness, D. J. |author2=Anderson, S. S. |author3=Cox, C. R. |year=1982 |title=Functions of female aggression during the pupping and mating season of grey seals, ''Halichoerus grypus'' (Fabricius) |journal=Canadian Journal of Zoology |volume=60 |issue=10 |pages=2270–2278 |doi=10.1139/z82-293}}</ref> Dominant female elephant seals stay in the center of the colony where they in the domain of a more dominant male, while marginal females are left with subordinates.<ref>{{cite journal |author1=Reiter, J. |author2=Panken, K. J. |author3=Le Boeuf, B. J. |year=1981 |title=Female competition and reproductive success in northern elephant seals |journal=Animal Behaviour |volume=29 |issue=3 |pages=670–687 |doi=10.1016/S0003-3472(81)80002-4|s2cid=53144427 }}</ref> Female Steller sea lions may solicit their territorial males for mating.{{sfn|Riedman|1990|p=215}}