Editing Baikal seal (section)

==Biology==
Their main food source is the [[golomyanka]], a [[cottoidea|cottoid oilfish]] found only in Lake Baikal. Baikal seals eat more than half of the annually produced biomass of golomyanka, some 64,000 tons.<ref name=Pastukhov/> In the winter and spring, it is estimated that more than 90% of its food consists of golomyankas.<ref name=zooex/><ref name=scfh>{{cite web| title=Mysterious Fish of Lake Baikal | url=https://scfh.ru/en/papers/mysterious-fish-of-lake-baikal/ | publisher=Science First Hand | volume=3, N2 | date=30 September 2004 | access-date=1 June 2017}}</ref> The remaining food sources for this seal are various other fish species, especially ''[[Cottocomephorus]]'' (about 7% of the diet during the winter and spring) and [[Kessler's sculpin]] (about 0.3% of the diet in the winter and spring), but it may also take some invertebrates such as ''[[Epischura baikalensis]]'', [[gammarid]]s and [[mollusc]]s.<ref name=zooex/> During the autumn the Baikal seal eats 50–67% fewer golomyankas than in the winter and spring, but significantly more ''Cottocomephorus'', Kessler's sculpins and [[stone sculpin]]s.<ref name=zooex/> A total of 29 fish species have been recorded in the diet.<ref name="iucn status 12 November 2021" /> They feed mainly during twilight and at night, when golomyankas occur in depths as shallow as {{convert|10-25|m|ft|abbr=on}}.<ref name="iucn status 12 November 2021" /><ref name=zooex/> During the day, golomyankas are typically found deeper than {{convert|100|m|ft|abbr=on}}.<ref name="iucn status 12 November 2021" /> Baikal seals can dive up to depths of {{convert|400|m|ft|abbr=on}}<ref name=zooex/> and stay underwater for more than 40 minutes.<ref name="iucn status 12 November 2021" /> Most dives last less than 10 minutes and generally only 2–4 minutes.<ref name="iucn status 12 November 2021" /> Baikal seals have two litres more blood than any other seal of their size and can stay underwater for up to 70 minutes if they are frightened or need to escape danger. According to a 2020 paper, Baikal seals also seek food through the use of [[filter-feeding]] on pelagic [[Amphipoda|amphipod]]s (''[[Macrohectopus branickii]]'') within Lake Baikal;<ref>{{Cite journal |last1=Watanabe |first1=Yuuki Y. |last2=Baranov |first2=Eugene A. |last3=Miyazaki |first3=Nobuyuki |date=2020-12-08 |title=Ultrahigh foraging rates of Baikal seals make tiny endemic amphipods profitable in Lake Baikal |journal=Proceedings of the National Academy of Sciences |volume=117 |issue=49 |pages=31242–31248 |doi=10.1073/pnas.2014021117 |pmc=7733859 |pmid=33199633|bibcode=2020PNAS..11731242W |doi-access=free }}</ref> they have specialized teeth that allow the seals to expel water while feeding, allowing them to gather large amounts of pelagic amphipods while swimming.

According to a 2004 paper on the [[foraging]] tactics of Baikal seals,<ref>{{Cite journal|last=Watanabe|first=Yuuki|date=September 2004|title=Foraging tactics of Baikal seals differ between day and night|url=https://www.int-res.com/articles/meps2004/279/m279p283.pdf|journal=Marine Ecology Progress Series|volume=279|pages=283–289|doi=10.3354/meps279283|bibcode=2004MEPS..279..283W |doi-access=free}}</ref> during the summer nights these seals are known to have different foraging strategies during night time and during day time. During the day, these seals use visual clues to search for their prey, which is mainly fish, while during the night they use tactile clues to hunt amphipods. Since it is brighter during the day, the seals are able to see much better in order to hunt for the fish. Since there is no light at night, they have to hunt with tactile cues. The amphipods they hunt at night have a [[Diel vertical migration|diel migration]], so they come up into shallower waters during the night, and swim to deeper waters during the day to escape predators.<ref>{{Cite journal|date=1993|title=Hydroacoustic measurement of the density of the Baikal macrozooplankter ''Macrohectopus branickii''|journal=Limnology and Oceanography|volume=38|issue=2|pages=425–434|doi=10.4319/lo.1993.38.2.0425|bibcode=1993LimOc..38..425.|doi-access=}}</ref> These seals were observed to dive deeper during dawn and dusk in order to get to these amphipods as they were swimming shallower and deeper, respectively.

The Baikal seal has been blamed for drops in [[omul]] numbers, but this is not the case. It is estimated that omul only comprises about 0.1% of its diet.<ref name=zooex/> The omul's main competitor is the golomyanka and by eating tons of these fish a year, Baikal seals cut down on the omul's competition for resources.<ref name=Pastukhov/>

Baikal seals have one unusual foraging habit. In early autumn, before the entire lake freezes over, they migrate to bays and coves and hunt Kessler's sculpin, a fish that lives in [[silt]]y areas which as a result, usually contains grit and silt in its digestive system. This grit scours the seals' gastrointestinal tracts and expels [[Intestinal parasite infection|parasites]].<ref name=Pastukhov/>

===Life history===
Female Baikal seals reach sexual maturity at 3–6 years of age, whereas males achieve it around 4–7 years.<ref name=SCS/> The males and females are not strongly [[sexually dimorphic]]. Baikal seals mate in the water towards the end of the pupping season. With a combination of delayed implantation and a nine-month [[gestation period]], the Baikal seals' overall pregnancy is around 11 months. Pregnant females are the only Baikal seals to [[hauling-out|haul out]] during the winter. The males tend to stay in the water, under the ice, all winter. Baikal seals are slightly [[Animal sexual behaviour#Polygamy|polygamous]] and slightly [[Territory (animal)|territorial]], although aren't particularly defensive of their territory. Males mate with around three females if given the chance. They then mark the female's [[Maternity den|den]] with a strong, [[musk]]y odor, which can be smelled by another male if he approaches. 
[[File:Baikal seal 4.jpg|thumb|[[Taxidermied]] pup in [[model]] of den]]
Females usually give birth to one pup, but they are one of only two species of true seals with the ability to give birth to twins.<ref name=Pastukhov/> Very rarely, triplets or quadruplets have been recorded.<ref name=zooex/> The twins often stick together for some time after being weaned. The females, after giving birth to their pups on the ice in late winter, become immediately impregnated again, and often are [[Lactation|lactating]] while pregnant. The female raises the pups on her own; she digs them a fairly large den under the ice, up to {{Convert|5|m}} in length, and more than {{Convert|2|m}} wide. Pups as young as two days old then further expand this den by digging a maze of tunnels around the den. Since the pup avoids breaking the surface with these tunnels, this activity is thought to be mainly for [[exercise]], to keep warm until they have built up an insulating layer of [[blubber]].

Baikal seal pups are [[weaned]] after 2–2.5 months, occasionally up to  3.5 months.<ref name="iucn status 12 November 2021" /> During this time, the pups can increase their birth weight five-fold. After the pups are weaned, the mother introduces them to solid food, bringing amphipods, fish, and other food into the den. In spring, when the ice melts and the dens usually collapses, the pup(s) is left to fend for itself. Growth continues until they are 20 to 25 years old. The only known natural predator of adult Baikal seals is the [[East Siberian brown bear|brown bear]], but this is not believed to occur frequently.<ref name="iucn status 12 November 2021" /> The seal pups are typically hidden in a den, but can fall prey to smaller land predators such as the [[red fox]], the [[sable]] and the [[white-tailed eagle]].<ref name=zooex/>

Every year in the late winter and spring, both sexes haul themselves out and begin to [[moult]] their weathered coat from the previous year, which is replaced with new fur. While moulting, they refrain from eating and enter a lethargic state, during which time they can die of overheating, males especially, from lying on the ice too long in the sun.<ref name=Pastukhov/> During the spring and summer, groups as large as 500 can form on the ice floes and shores of Lake Baikal. Baikal seals can live to over 50 years old, exceptionally old for a seal,<ref name=Pastukhov/> although the females are presumed to be fertile only until they are around 30.<ref name=animaldiversity>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Phoca_Sibirica.html Harrold, A. 2002. “Phoca Sibirica” (on-line), Animal Diversity Web.] Accessed August 27, 2007.</ref>