Editing Baikal seal

{{Short description|Species of freshwater seal}}
{{Speciesbox
| name = Baikal seal
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 12 November 2021">{{cite iucn |author=Goodman, S. |date=2016 |title=''Pusa sibirica'' |volume=2016 |page=e.T41676A45231738 |doi=10.2305/IUCN.UK.2016-1.RLTS.T41676A45231738.en |access-date=12 November 2021}}</ref> 
| image = Nerpa (Pusa sibirica) (3635255975).jpg
| genus = Pusa
| species = sibirica
| authority = [[Johann Friedrich Gmelin|Gmelin]], 1788
| range_map = Baikal Seal area.png
| range_map_caption = Baikal seal range
| synonyms =''Phoca sibirica''
}}
The '''Baikal seal''' ('''''Pusa sibirica'''''), [[Common name|also known]] as '''Lake Baikal seal''' or '''Baikal nerpa''' ({{Lang|ru|[[wikt:нерпа|нерпа]]|italic=yes}}), 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 [[freshwater pinniped]] species.<ref name="MMOTW">{{cite book |first=Randall R. |last=Reeves |first2=Brent S. |last2=Stewart |first3=Phillip J. |last3=Clapham |first4=James A. |last4=Powell |title=National Audubon Society Guide to the Marine Mammals of the World |publisher=Alfred A. Knopf |location=New York |year=2002 |isbn=0-375-41141-0 }}</ref> The related [[Caspian seal]] inhabits another large, inland body of water, the [[Caspian Sea]]. Both species are closely related to the [[ringed seal]], which inhabits the [[Arctic Ocean]]. 

A subpopulation of inland [[harbour seal]]s living in the [[Hudson Bay]] region of Quebec, Canada (the [[Lacs des Loups Marins]] harbour seals), as well as the [[Saimaa ringed seal]] and the [[Ladoga seal]] (both ringed seal subspecies), are also found in fresh water, but these seals are part of species that also have marine populations, instead of being [[Biological specificity|distinct species]].<ref name="MMOTW"/> 

The most recent population estimates are 80,000 to 100,000 animals, roughly equaling the expected [[carrying capacity]] of the lake. At present, the species is not considered threatened.<ref name="iucn status 12 November 2021" />

==Description==
[[File:Baikal-seal 4747-pho.jpg|thumb|A young seal]]
The Baikal seal is one of the smallest true seals. Adults typically grow to {{convert|1.1-1.4|m|ftin|abbr=on}} in length<ref name="iucn status 12 November 2021" /> with a body mass from {{convert|abbr=on|63|to|70|kg|lb}}.<ref name=SCS>{{cite web|url=http://www.pinnipeds.org/species/baikal.htm |title=Baikal Seal (Phoca Sibirica) |publisher=Seal Conservation Society |access-date=2007-09-27 |archive-url=https://web.archive.org/web/20071006193844/http://www.pinnipeds.org/species/baikal.htm |archive-date=6 October 2007 |url-status=dead }}</ref> The maximum reported size is {{convert|1.65|m|ftin|abbr=on}} in length and {{convert|130|kg|lb|abbr=on}} in weight.<ref name=zooex>{{cite web| title=Baikal seal | url=http://baikal.ru/en/baikal/excursion/nerpa.html | publisher=baikal.ru | access-date=1 June 2017}}</ref> There are significant annual variations in the weight, with lowest weight in the spring and highest weight, about 38–42% more, in the fall.<ref name=Pastukhov>{{cite web| url=http://www.bww.irk.ru/baikalseals/baikalseals_01.html| title=The Face of Baikal – Nerpa| author=Pastukhov, Vladimir D.| publisher=Baikal Web World| access-date=2007-09-27| archive-url= https://web.archive.org/web/20071025051137/http://www.bww.irk.ru/baikalseals/baikalseals_01.html| archive-date= 25 October 2007 | url-status= live}}</ref> The animals show very little [[sexual dimorphism]]; males are only slightly larger than females.<ref name=SCS/> They have a uniform, [[Steel (color)|steely]]-grey coat on their backs and fur with a yellowish tinge on their abdomens. As the coat weathers, it becomes brownish.<ref name=Pastukhov/> When born, the pups weigh {{convert|3-3.5|kg|lb|abbr=on}} and are about {{convert|70|cm|ftin|abbr=on}} long.<ref name="iucn status 12 November 2021" /> They have coats of white, silky, natal fur. This fur is quickly shed and exchanged for a darker coat, much like that of adults. Rarely, Baikal seals can be found with spotted coats.<ref name=SCS/>
===Evolution===
The skull structure of the Baikal seal suggests it is closely related to the [[Caspian seal]]. In addition, the morphological structures in both species suggest they are descended from Arctic [[ringed seal]]s.<ref>{{cite journal|last1=Endo|first1=H.|last2=Sakata|first2=S.|last3=Arai|first3=T.|last4=Miyazaki|first4=N.|title=The Muscles of Mastication in the Caspian Seal (''Phoca caspica'')|journal= Anatomia, Histologia, Embryologia|date=April 2001|volume= 31|issue= 5|pages=262–265|doi=10.1046/j.1439-0264.2002.00372.x|pmid=12484416|s2cid=30684638}}</ref> In prehistory, they may have swum up rivers and streams, or there is the possibility that Lake Baikal was linked to the ocean at some point through a large body of water, such as the [[Paratethys Sea]], [[West Siberian Glacial Lake]] or [[West Siberian Plain]], formed in a previous [[ice age]]. The seals are estimated to have inhabited Lake Baikal for some two million years.<ref>{{cite journal |last1=Palo |first1=Jukka U. |last2=Väinölä |first2=Risto |title=The enigma of the landlocked Baikal and Caspian seals addressed through phylogeny of phocine mitochondrial sequences|journal=Biological Journal of the Linnean Society |date=2006 |volume=88 |issue=1 |pages=61–72 |doi=10.1111/j.1095-8312.2006.00607.x|doi-access=free}}</ref>

==Distribution==
[[File:Из жизни байкальской нерпы близ Ушканьих островов 03.jpg|thumb|left|Group of Baikal seals hauling out on a rock around [[Ushkan Islands]], [[Barguzinsky District|Barguzinsky district]]]] 
The Baikal seal lives only in the waters of [[Lake Baikal]]; they are [[Endemism|endemic]] there.<ref name=Schofield2001>{{cite news| url=http://www.themoscowtimes.com/stories/2001/07/27/106.html| title=Lake Baikal's Vanishing Nerpa Seal| last=Schofield| first=James| newspaper=[[The Moscow Times]]| date=27 July 2001| access-date=2007-09-27}}</ref> 

The areas of the lake in which the Baikal seals reside change depending on the season, as well as other [[Natural environment|environmental]] factors. They are solitary animals for the majority of the year, sometimes living kilometres away from other Baikal seals. In general, a higher concentration of Baikal seals is found in the northern parts of the lake, because the longer winter keeps the ice frozen longer, which is preferable for pupping.<ref name=Pastukhov/> However, in recent years, migrations to the southern half of the lake have occurred, possibly to evade [[Seal hunting|hunters]].<ref name=SCS/> In winter, when the lake is frozen over, seals maintain a few breathing holes over a given area and tend to remain nearby, not interfering with the food supplies of nearby seals. When the ice begins to melt, Baikal seals tend to keep to the shoreline.

==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>

==Relation to humans and conservation==
[[Image:Nerpa festival.JPG|thumb|A Baikal seal mascot at the Nerpa Festival in [[Irkutsk]]]]
Since 2008, the Baikal seal has been listed as a [[Least Concern]] species on the [[IUCN Red List]].<ref name="iucn status 12 November 2021" /> This means that they are not currently [[threatened]] or [[endangered]]. In 1994, the Russian government estimated that they numbered 104,000. In 2000, [[Greenpeace]] performed its own count and found an estimated 55,000 to 65,000 seals.<ref name=Schofield2001/> The most recent estimates are 80,000–100,000 animals, roughly equaling the carrying capacity of the lake.<ref name="iucn status 12 November 2021" />

In the last century, the kill quota for hunting Baikal seals was raised several times,{{When|date=May 2025}} most notably after the [[fur]] industry boomed in the late 1970s and when official counts began indicating more Baikal seals were present than previously known.<ref name=Pastukhov/> The quota in 1999, 6,000, was lowered in 2000 to 3,500, which was still nearly 5% of the population; if the Greenpeace count is correct.<ref name=SCS/> In 2013–2014, the hunting quota was set at 2,500.<ref name="iucn status 12 November 2021" /> In addition, new techniques, such as netting breathing holes and seal dens to catch pups, have been introduced. In 2001, a prime seal pelt would bring 1,000 [[Russian ruble|ruble]]s at market.<ref name=Schofield2001/> In 2004–2006, about 2,000 seals were killed per year according to official Russian statistics, but in the same period another 1,500–4,000 are thought to have died annually due to drowning in fishing gear, poaching, and the like.<ref name="iucn status 12 November 2021" /> In 2012–2013, it was estimated that 2,300–2,800 were hunted per year (combined legal hunting and poaching).<ref name="iucn status 12 November 2021" /> Some groups have pressured for higher hunting quotas.<ref name="iucn status 12 November 2021" />
[[File:Baikal seal 1.jpg|thumb|left|In the Baikal Museum, [[Listvyanka, Irkutsky District, Irkutsk Oblast|Listvyanka]]]]
Another problem at Lake Baikal is the [[Water pollution|introduction of pollutants]] into the ecosystem;[[pesticides]] such as [[DDT]] and [[hexachlorocyclohexane]], as well as [[industrial waste]], mainly from the Baikalisk [[pulp and paper]] plant, are thought to have exacerbated several disease epidemics among Baikal seal populations. The chemicals are speculated to [[Bioaccumulation|concentrate up]] the [[food chain]] and weaken the Baikal seal's immune system, making them susceptible to diseases such as [[canine distemper]] and [[Yersinia pestis|the plague]], which was the cause of a serious Baikal seal mortality event that killed 5,000–6,500 animals in 1987–1988.<ref name="iucn status 12 November 2021" /><ref name=SCS/> Small numbers died as recently as 2000, but the reason for their deaths is unclear.<ref name=SCS/> Canine distemper is still present in the Baikal seal population, but has not caused mass deaths since the earlier outbreaks.<ref name="iucn status 12 November 2021" /> In general, levels of DDT and non-ortho [[Polychlorinated biphenyl|PCB]] have declined in the lake from the 1990s, levels of mono-ortho PCB are unchanged, and the level of [[perfluorochemical]]s have increased. At present, Baikal seals show lower levels of contaminants than seals of Europe and North America, but higher than those in the Arctic. Industrialization of the area near Lake Baikal is increasing and future monitoring is necessary.<ref name="iucn status 12 November 2021" />

The most serious future threat to the survival of the seal may be [[global warming]], which has the potential to seriously affect a closed cold-water ecosystem such as that of Lake Baikal.<ref name="iucn status 12 November 2021" />

==References==
{{Reflist|30em}}

==External links==
* Peter Saundry. 2010. [http://www.eoearth.org/article/Baikal_Seal Baikal seal]. Encyclopedia of Earth. topic editor: C. Michael Hogan; ed. in-chief: Cutler J. Cleveland. Washington, DC (Accessed May 21, 2010)
*[https://web.archive.org/web/20070927210833/http://www.earthisland.org/project/reportpage2.cfm?reportcontentID=11&subSiteID=1&pageID=71 Earth Island Institute. “The Lake Baikal Seal: Already Endangered” (on-line), Baikal Watch.] (Accessed March 6, 2004; archive.org link added August 25, 2010.)

{{Carnivora|C1.}}
{{Taxonbar|from=Q4535}}
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{{DEFAULTSORT:Baikal Seal}}
[[Category:Phocins]]
[[Category:Fauna of Lake Baikal]]
[[Category:Endemic fauna of Russia]]
[[Category:Pinnipeds of Asia]]
[[Category:Mammals described in 1788]]
[[Category:Taxa named by Johann Friedrich Gmelin]]