Editing Baikal seal (section)

===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>