Baikal Seal

## About

A pair of Baikal seals at Crocus City Oceanarium, Russia.

The Baikal seal ***(Pusa sibirica)*** also commonly known as the nerpa, is a species of true-seal that is found exclusively in the Russian lake, Lake Baikal. The seals have rounded bodies that taper towards the hind flippers, which stretch outward from the main body, inhibiting dexterity on land. Like all true-seals, the Baikal seal propels itself on land through the use of dragging its body, or bouncing in an undulating motion. adult Baikal seals have black or silver coats, with long whiskers and large dark eyes. Some individuals may also possess mottled or spotted patterning however, this is uncommon. Juvenile Baikal seals are covered in non-waterproof hair known as lanugo. The lanugo is silky, short and silverish-white. The Baikal seal is the smallest pinniped species. They typically grow to a length of 1-1.4m (3.2-4.5ft) and can weigh 50-130kg (110-286lbs) however, males are typically larger than females.

## Diet

Baikal seals hunt pelagic commercially valuable fish, which has led to amounts of human-wildlife conflict however, they are also known to hunt commercially invaluable fish as well as multiple species of invertebrates. Baikal seals are known to be most active hunters during the twilight and night hours, where young individuals have been observed diving 100m (328ft) for up to 10 minutes, in order to catch their prey.

## Conservation Status

Though Baikal seals are classed least concern species by the IUCN, the species is not exempt of threats. The rivers that feed into Lake Baikal are incredibly industrialised and present concerns of contamination by polycholorinated biphenyls (PCBs), dichlorodiphenyltricholoethanes (DDTs) and other similar chemicals. It has been hypothesised that prolonged exposure to such biohazards, can cause infertility and immunocompetence in seals. Contaminant levels assessed in Baikal seals from the 1990s-2015 exhibit a trend in which PCBs and DDTs decline in abundance, whether as mono-ortho PBCs showed no decreasing trend and perfluorochemicals increased in frequency. This data represents the changes in industrialised areas and how it can affect inflow of chemical compounds. Observations relating to the contaminant burdens of Baikal seal specimens, have led to the species being considered having a lower level when compared to North American and European Pinniped species, yet a higher level than most Arctic species. Specimens examined in 2005 concluded that 40% of the individuals had TEQ (Toxic Equivalent – a measurement used for summarising the relative toxicity of complex contaminant mixtures). Levels recorded above the species' thresh-hold aligned with immune repressive effects in harbour seals (***Phoca vitulina)***. Older adult male seals are vulnerable to organochlorine accumulation, as it is age related however, due to the difficulty of demonstrating the effects of contaminants in the wilderness, it cannot currently be proven that contamination inhibits the disease susceptibility or demographics of the Baikal seal population, according to the IUCN. More recent studies related to the liver gene expression in Baikal seals, suggest that fluctuations in liver metabolisms, are consistent with toxicity in relation to immediate contaminant exposure however, the significance this holds in relation to health is unclear. Due to further industrialisation, it is important that further monitoring of the contaminant exposure in Lake Baikal is continued. An outbreak of canine distemper virus (CDV) in the years of 1987-1988, likely caused by transition from feral dogs, caused the casualties of 6,500 Baikal seals. Recent surveys have also concluded that CDV is currently in circulation throughout the population, with this it is advised that monitoring of CDV circulation is Baikal seals remains prioritised. Lastly, it is apparent that the Baikal seal population is threatened by the effects of climate change in the future. As the Baikal seal is an ice breeding pinniped, its breeding grounds may not be permanent in the near future. Coupling this with the fact that the Baikal seal is a land licked species and thus has no available alternative habitats, shows that the species' population stability is uncertain.

## Range and Population

As its name suggests, the Baikal seal is endemic to Lake Baikal in Russia and occasionally the rivers that feed into the Baikal. This makes the Baikal seal, uniquely the only freshwater seal species. Baikal seals seek out cooler temperatures, breeding on ice sheets. The places in which they inhabit, are often dictated by the ice conditions of Lake Baikal and surrounding rivers. Currently the population of Baikal seals lies at around 54,000 mature individuals. Luckily the seal's population is regarded as stable.

## Behaviour

Breeding season takes place for Baikal seals in May and females experience a minor period of delayed implantation. Gestation last for 9 months and pups are born on the ice sheets during February-March. Interestingly, if two pups are born, both typically survive. The pair will stay together until weaned and then congregate around each other for an extended amount of time afterwards. Like other seal species, pups are born with a soft white coast known as lanugo. Lanugo is not waterproof, meaning that pups cannot swim without becoming incredibly susceptible to freezing. The seals will typically molt this coat during Spring on the ice sheets however, if the ice sheets have melted, the will continue their molt on the closest shores. During the 1990's a group of juvenile seals where radio tagged, revealing that juvenile Baikal seals may travel from 400-1,600km (248-994mi) across Lake Baikal in the months from September-May. Due to the accumulation of ice during Winter months, Baikal seals only swim near breathing holes that they manufacture in the ice's surface. These holes are maintained by the constant scratching that Baikal seals do with their sharp claws however, some individuals may also use their teeth or heads. Though immature seals will only upkeep one hole, Adults typically have many auxiliary openings to a single hole. The demographics of the Baikal seal dictates where an individuals will reside, for example; males will congregate throughout the Central Baikal, whereas females will congregate on the East coast. Groups of immature seals of both sex inhabit the West coast and pregnant females remain on the ice for the majority of Winter. Typically solitary during Winter, Baikal seals will only come together in large groups to feed once the season has proceeded (April), around places where ice has began to melt. During Summer the seals will haul-out on shore in the Southeastern Baikal however, once Autumn returns, the seals move back into areas where ice begins forming. Large groups comprised of 200-500 Baikal seals may congregate in places of favourable habitat during Spring, even sharing access holes.

### Relationship with Humans

Baikal seals are known to harm the fishing industry, as they hunt extremely commercial important fish such as members of the Comephorus genus. Unlike the related and friendly Caspian seals ***(Pusa Caspica)***, Baikal seals avoid fishing vessels and humans and may even dive for up to 2-3 times longer than their average of 20-25 minutes, when frightened by a human. Baikal seals are known to hunt most prolifically at the twilight and night hours, diving to depths of 100m (328ft) in search of prey. The abnormally large eyes of the Baikal seal reflect this behavioural adaptation.

## In Captivity

Baikal seals can only be found in Russian institutes, with the exception of Zoologischer Garten Leipzig, Germany. Baikal seals are culturally iconic in Russia and it is no surprise as to why they are such a popular zoo specimen in the country.

## Sources

* IUCN Red List of Threatened Species - https://www.iucnredlist.org/species/41676/45231738
* Baikal Seal | ZOOINSTITUTES - https://zooinstitutes.com/animals/baikal-seal-2841/
* Baikal Seal | Animal Diversity Web, University of Michigan Museum of Zoology - https://animaldiversity.org/accounts/Pusa\_sibirica/