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BiologyA year in the life of the Baikal seal is heavily driven by the unique habitat in which it is found (1). During winter, when the lake is largely covered with ice, seals can be found throughout the lake, particularly in the deep water in the centre (1), utilizing holes in the ice to breathe (2). The Baikal seal uses its strong foreclaws, as well as its head, teeth and rear flippers, to keep these vital access holes open (2). Although the Baikal seal is a largely solitary animal, several individuals may share access holes, and at certain times of the year, large groups may gather in areas of favourable habitat, such as around April, when the ice begins to break up and the seals start to congregate at new openings in the ice to feed (2). The month of May marks the peak of the breeding season. Male Baikal seals are believed to be polygynous, meaning that they mate with more than one female (2). Mating is thought to take place underwater, and it is suspected that there is delayed implantation (2). In late winter and early spring, following a gestation period of nine months (2), pregnant females move onto the ice, where they build an ice den in which the pup is born (1). The home range of each female on the ice, which incorporates the den and breathing holes, does not overlap with other females (1). Baikal seals typically give birth to just one pup, although twins, whilst uncommon, are more frequent than in other pinnipeds (2). The newborn seals, camouflaged on the ice with their white, woolly coats, do not enter the water until two or three weeks old (1). At six weeks of age, the pup's white coat begins to be replaced with the darker, adult fur, and they are fed milk by their mother until up until 2.5 months. Male Baikal seals become sexually mature at seven years of age, while females reach sexual maturity about a year earlier (2). They can continue to reproduce until 43 to 45 years of age (1), and with a maximum recorded life span of 56 years (2), this species may have the greatest longevity of any pinniped (1). As the ice breaks up further in May and June, the Baikal seal undergoes its annual molt (1) (2), while summer sees the seals concentrating in the southeastern part of the lake, where they haul themselves onto the shore and rocky islands between feeding trips (1). The Baikal seal feeds primarily on fish species which have no commercial value to humans (2), and juvenile seals may also consume amphipods (1). It feeds mainly at twilight and during the night, diving down to typical depths of 10 to 50 metres for 2 to 4 minutes to hunt its prey (1).