The Saimaa ringed seal (Pusa saimensis, Finnish: saimaannorppa) is a species of seal. It is among the most endangered seals in the world, having a total population of only about 500 individuals. The only existing population of these seals is found in Lake Saimaa, Finland. It has lived in complete isolation from other ringed seal populations for around 9,500 years, and have diverged into a morphologically and ecologically different species or subspecies. The population is descended from ringed seals that were separated from the rest when the land rose after the last ice age. This seal, along with the Baikal seal, the Ladoga seal, and the Ungava seal, is one of the few living freshwater seals. The Saimaa ringed seal was previously considered a subspecies of ringed seal called Pusa hispida saimensis, but in 2025 was classified as its own species after genetic research revealed its closest living relatives being ringed seals from arctic North America, rather than Baltic and Ladogan ringed seals as was previously thought, and having diverged as far back as 60 000 years ago to form its own evolutionary branch.
Distribution
Habitat
The Saimaa ringed seal is endemic to their habitat in Lake Saimaa, Finland. The lake lies between the cities of Lappeenranta in the south and Joensuu in the north, spanning an oval of approximately 180 by 140 km (112 by 87 mi). It consists of numerous larger basins connected by narrower glacier-carved channels, and its geography is maze-like, having 13,710 islands, an approximate coastline length of 14,850 kilometres (9,230 mi), and a surface area of 4,279 km2 (1,652 mi2). It is relatively shallow, having an average depth of 17 metres (56 ft) and a maximum depth of 85.8 m (281 ft). The freshwater lake freezes over between the months of November and May, leaving the seals both an ice habitat and an open water habitat. During summer months when the ice is melted, these islands provide ample space for the seals for moulting and breeding.
Range Saimaa ringed seals are named as such due to their only habitat being Lake Saimaa, Finland. Thus, their range is restricted only to the waters of Lake Saimaa and its surrounding banks.
Appearance
An adult Saimaa ringed seal is between 85 and 160 centimetres (2.79 and 5.25 ft) in length and weighs between 50 and 90 kilograms (110 and 200 lb), males usually being larger than females. They are dark grey, with a grey-black dorsal with circular white rings. The bottom of the seal is light grey. The Saimaa ringed seal is darker than any other ringed seal.
Diet The Saimaa ringed seal does not have an incredibly varied diet. They are generalist feeders and exclusively eat fish. The fish consumed consist primarily of small schooling fish averaging 8.6 cm in length and up to 21 cm in length, while it has been shown that the pups eat slightly smaller fish than the average. The majority of their diet consists of vendace, smelt, perch, and roach. The pups' diet varies markedly from the adults' in that their diet consists primarily of perch and roach found in the shallow water where they spend most of their time in their earlier months, while the adults consume more vendace and smelt. It was believed for a long time that the Saimaa ringed seal was competing with the commercial and recreational fishing industries and there were bounties paid on them until the 1940s. However, it has recently been proven that the Saimaa ringed seal has minimal to no effect on the fishing industry. They do not prey on the local endangered salmon species (Salmo salar, S. trutta lacustris, and Salvelinus alpinus). Although they do prey on the valuable vendace population, the proportion of the vendace population to the amount consumed by the seals indicates that they do not compete with the local fishing industries.
Behaviour
Reproduction Saimaa ringed seals become mature between the ages of 4 and 6 years. Their pregnancy rate is between 80 and 95 percent. Their gestation lasts 11 months. Their pups are between 55 and 65 centimetres (1.80 and 2.13 ft), and 4 to 5 kilograms (8.8 to 11.0 lb) at birth. The Saimaa ringed seal's longevity is just over 20 years. A study conducted from 1980–84 revealed that Saimaa ringed seals make burrowed dens close to the shore and they reproduce once a year due to their longevity. Saimaa ringed seals have two kinds of lairs or dens; they have a haul-out lair where no breeding takes place, and the breeding lair. Breeding lairs are located closer to the shore than haul-out dens.
Diving Diving is an important behaviour for aquatic mammals as it is something they rely on for behaviours such as foraging and travelling. The duration of their dives increases from spring to autumn, which may be a result of food availability, but it is interesting because they are one of the few landlocked seal species. Many studies have been done to observe Saimaa ringed seal diving, which was discovered to last longer than expected. Their average time for a long dive was recorded at 15 minutes and it was believed to be an aerobic resting dive. The average dive depth ranges from 10 to 15 m; however, their maximum dive depths were limited by environmental depth. The Saimaa ringed seal has also been observed to have seasonal hauling-out patterns. In May and June, when the seals are moulting, they are observed to haul out both day and night; however, in late summer they are observed to haul out only at night. The Saimaa ringed seal is able to complete its dives and navigate in its environment due to its highly developed vibrissae, also known as whiskers. Using their vibrissae, they are able to detect sound and pressure waves in their otherwise dark environment.
Conservation
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