Nerpa
Encyclopedia
The Baikal seal, Lake Baikal seal, or Nerpa (Pusa sibirica, obsolete: Phoca sibirica), is a species of earless seal
Earless seal
The true seals or earless seals are one of the three main groups of mammals within the seal superfamily, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae...

 endemic to Lake Baikal
Lake Baikal
Lake Baikal is the world's oldest at 30 million years old and deepest lake with an average depth of 744.4 metres.Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the...

 in Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

. Like the Caspian seal
Caspian Seal
Caspian seals , one of the smallest members of the earless seal family, are unique in that they are found exclusively in the brackish Caspian Sea. They can be found not only along the shorelines, but also on the many rocky islands and floating blocks of ice that dot the Caspian Sea...

, they are related to the Arctic ringed seal
Ringed Seal
The ringed seal , also known as the jar seal and as netsik or nattiq by the Inuit, is an earless seal inhabiting the Arctic and sub-Arctic regions...

. The Baikal Seal is the smallest of the true seals, and with the exception of a sub-population of inland harbour seals living in the Hudson Bay region of Quebec, Canada (lac de loups marins harbour seals), they are the only exclusively freshwater pinniped species.

It remains a scientific mystery how the seals originally came to Lake Baikal, hundreds of kilometers from any ocean. Some scientists speculate the seals arrived at Lake Baikal when a sea-passage linked the lake with the Arctic Ocean
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...

 (see also West Siberian Glacial Lake
West Siberian Glacial Lake
The West Siberian Glacial Lake, also known as West Siberian Lake, or Mansiyskoe Lake , was a periglacial lake formed when the Arctic Ocean outlets for each of the Ob and Yenisei rivers were blocked by the Barents-Kara Ice Sheet during the Weichselian Glaciation, approximately 80,000 years ago...

 and West Siberian Plain
West Siberian Plain
The West Siberian Plain is a large plain that occupies the western portion of Siberia, between the Ural Mountains in the west and the Yenisei River in the east, and by the Altay Mountains on the South-East. Much of the plain is poorly drained and consists of some of the world's largest swamps and...

).

The total population is estimated to be over 60,000 animals, and hunting of the seals, once widespread, is now restricted.

Statistics

  • Weight: 70 kg (155 lb) average, 150 kg (330 lb) maximum
  • Length: 1.3 m (4 ft 3 in) average
  • Food: mainly golomyanka
    Golomyanka
    The golomyankas or Baikal oilfish are two species of peculiar sculpin-like fishes endemic to Lake Baikal in Russia.-Description:...

     and goby
    Goby
    The gobies form the family Gobiidae, which is one of the largest families of fish, with more than 2,000 species in more than 200 genera. Most are relatively small, typically less than 10 cm in length...

  • Litter: usually one pup
    Pup
    Pup may refer to:In zoology:*Puppies, younger dogs*Pinniped young*Shark young*Rodent youngIn other uses:* Sopwith Pup, an aircraft used by the British in World War I* Beagle Pup, a 1960s British light aircraft...

    , sometimes two
  • Diving time: usually 20–25 minutes (45–60 minutes maximum)


Description

The Baikal seal is one of the smallest true seals. The adult grows to be around 1.3 m (4 ft 3 in) in length with body mass from 63 to 70 kg (140 to 155 lb). The animals show very little sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

; the males are only slightly larger than the females. They have a uniform steely-grey coat on their backs and fur with a slightly more yellow tinge coating their abdomens. As the coat weathers, it becomes brownish. When first born, pups are around 4.5 kg (10 lb) and have a coating of white silky natal fur. This fur is quickly shed and exchanged for a darker coat, much like that of the adult. Rare Baikal seals can be found with spotted coats.

Distribution

The Baikal seal lives only in the waters of Lake Baikal. It is something of a mystery how Baikal seals came to live there in the first place. It can be speculated they swam up rivers and streams or possibly Lake Baikal was linked to the ocean at one point as the result of a large body of water, such as the West Siberian Glacial Lake
West Siberian Glacial Lake
The West Siberian Glacial Lake, also known as West Siberian Lake, or Mansiyskoe Lake , was a periglacial lake formed when the Arctic Ocean outlets for each of the Ob and Yenisei rivers were blocked by the Barents-Kara Ice Sheet during the Weichselian Glaciation, approximately 80,000 years ago...

 or West Siberian Plain
West Siberian Plain
The West Siberian Plain is a large plain that occupies the western portion of Siberia, between the Ural Mountains in the west and the Yenisei River in the east, and by the Altay Mountains on the South-East. Much of the plain is poorly drained and consists of some of the world's largest swamps and...

, formed in a previous ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

. No one knows, but it is estimated seals have inhabited Lake Baikal for some two million years. The Baikal seal, the Saimaa Ringed Seal
Saimaa Ringed Seal
The Saimaa ringed seal The Saimaa ringed seal The Saimaa ringed seal (Pusa hispida saimensis, is a subspecies of ringed seal (Pusa hispida). They are among the most endangered seals in the world, having a total population of only about 260 individuals. The only existing population of these seals is...

 (Pusa hispida saimensis), and the Ladoga seal
Ladoga Seal
The Ladoga ringed seal , is a freshwater subspecies of the ringed seal which are found entirely in Lake Ladoga in northwestern Russia. The subspecies evolved during the last ice age, about 11,000 years ago...

 (Pusa hispida ladogensis) are the only exclusively freshwater seals.

The areas of the lake in which the Baikal seals reside changes depending on the season as well as some other environmental
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....

 factors. Baikal seals are solitary animals for the majority of the year, sometimes living kilometers away from other Baikal seals. In general, there is a higher concentration of Baikal seals in the northern parts of the lake, because the longer winter keeps the ice frozen for longer, which is preferable for pupping. However, in recent years there have been migrations to the southern half of the lake. These are speculated to evade hunters. 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 a nearby neighbour. When the ice begins to melt, the Baikal seals tend to keep to the shoreline.

Abundance and trends

As of 2007, the Baikal seal is listed as a “lower risk” species on conservation lists. This means that while they are not currently threatened or endangered, it is possible and even likely they will be in the near future. At last official count, by the Russian government in 1994, they numbered 104,000. In 2000, Greenpeace
Greenpeace
Greenpeace is a non-governmental environmental organization with offices in over forty countries and with an international coordinating body in Amsterdam, The Netherlands...

 performed its own count and came up with somewhere from 55,000 to 65,000 seals. It is thought excessive hunting, as well as less severe problems of poaching and pollution, are quickly reducing the population.

In the last century, the kill quota for hunting Baikal seals was raised several times, most notably after the fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...

 industry boomed in the late 1970s and when official counts began indicating there were more Baikal seals than previously known. The quota in 1999 was 6,000, lowered in 2000 to 3,500 which is still nearly 5% of the Baikal Seal population if the Greenpeace count is correct. In addition, new techniques, such as netting breathing holes, and seal dens to catch pups have been introduced. In one area, 3,000 out of 4,000 breathing holes had been netted, many probably illegally. One prime seal pelt will bring 1,000 ruble
Russian ruble
The ruble or rouble is the currency of the Russian Federation and the two partially recognized republics of Abkhazia and South Ossetia. Formerly, the ruble was also the currency of the Russian Empire and the Soviet Union prior to their breakups. Belarus and Transnistria also use currencies with...

s at market, more than a month’s salary.

Lake Baikal has eight wildlife patrol officers, which amounts to one officer for roughly 2,500 square kilometers, making enforcement of regulations difficult. Even without poaching, hunting, even on a small quota, is a problem, because many of the seals that are shot or injured still escape, and die later. These do not fall under the kill quota and are tacked on after. It is unlikely poaching and hunting will slow considerably without government intervention.

The other problem at Lake Baikal is the introduction of pollutants into the ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

. Pesticides such as DDT
DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....

 and Hexachlorocyclohexane
Hexachlorocyclohexane
Hexachlorocyclohexane or 666 is a six chlorine substituted cyclohexane, a polyhalogenated compound. It comes in many forms. Some are pesticides.Common forms are:* α-HCH , or α-BCH, alpha-Hexachlorocyclohexane...

, as well as industrial waste, mainly from the Baikalisk pulp and paper plant, have thought to have been the cause of several disease epidemics among the Baikal Seal. The speculation is that the chemicals work their way up the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

, and weaken the Baikal seal's immune systems, making them susceptible to diseases such as canine distemper
Canine distemper
Canine distemper is a viral disease that affects animals in the families Canidae, Mustelidae, Mephitidae, Hyaenidae, Ailuridae, Procyonidae, Pinnipedia, some Viverridae and Felidae...

 and the plague, which was the cause of a serious Baikal seal epidemic that resulted in the deaths of thousands of animals in 1997 and 1999.

Reproduction

Female Baikal seals reach sexual maturity at 3–6 years of age, whereas males reach it around 4–7 years. 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 9-month gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...

, the Baikal seal’s overall pregnancy is around 11 months. Pregnant females are the only Baikal seals to haul out
Hauling-out
Hauling-out is the behaviour associated with pinnipeds , of temporarily leaving the water between periods of foraging activity for sites on land or ice...

 during the winter. The males tend to stay in the water, under the ice, all winter. Baikal seals usually give birth to one pup, but they are one of only two species of true seal with the ability to give birth to twins. The twins will often stick together for some time after being weaned. The females, after giving birth to their pups on the ice in late winter, will become immediately impregnated again, and will often be lactating while pregnant.

Baikal seals are slightly polygamous and slightly territorial, although not particularly defensive of this territory. Males will mate with around 3 females if given the chance. They then mark the female’s den with a strong musky odor, which can be smelled by another male if he approaches. The female raises the pups on her own; she will dig them a fairly large den under the ice, up to 5 m (16 ft) )in length, and more than 2 m (6 ft) wide. Pups as young as two days old will then further expand this den by digging a maze of tunnels around the den. Since the pup will avoid breaking the surface with these tunnels, it is thought that this activity is mainly for exercise, to keep warm until they have built up an insulating layer of blubber.

The mother Baikal seal will feed her young for around 2.5 months, nearly twice as long as any other seal. During this time, the pups can increase their birth weight (around 4 kg {9 lb}) fivefold. After the pups are weaned, the mother will introduce them to solid food, bringing shrimp, fish, and other edibles into the den.

In spring, when the ice melts and the dens usually collapse, the pup is left to fend for itself. Growth continues until they are 20 to 25 years old.

Every year in the late winter and spring, both sexes will haul themselves out and begin to moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...

 their coat of fur from the previous year, which will be replaced with a new one. While moulting they do not eat and enter a lethargic state, during which time they often die of overheating, males especially, from lying on the ice too long in the sun. 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, although they are presumed to be fertile only until they are around 40.

Foraging

The Baikal seal’s main food source is the golomyanka
Golomyanka
The golomyankas or Baikal oilfish are two species of peculiar sculpin-like fishes endemic to Lake Baikal in Russia.-Description:...

, found only in Lake Baikal. Baikal seals eat more than half of the annual produced biomass of golomyanka, some 64,000 tons. Baikal seals also eat some types of invertebrates, and the occasional omul
Omul
The omul, Coregonus migratorius, also known as Baikal omul , is a whitefish species of the salmon family endemic to Lake Baikal in Siberia, Russia. It is considered a delicacy and is the object of one of the largest commercial fisheries on Lake Baikal...

. They feed mainly at night, when the fish come within 100 m (330 ft) of the surface. They feed with 10-20 minute dives, although this is hardly the extent of their abilities. Baikal seals have two liters 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.

The Baikal seal is blamed for drops in omul numbers; however, this is not the case. 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.

Baikal seals do have one unusual foraging habit. In the early autumn, before the entire lake freezes, they migrate to bays and coves and hunt sculpin
Sculpin
A Sculpin is a fish that belongs to the order Scorpaeniformes, suborder Cottoidei and superfamily Cottoidea, that contains 11 families, 149 genera, and 756 species...

, a fish that lives in silty areas and as a result usually contains a lot of grit and silt in its stomach. This grit scours out the seal's innards and gets rid of parasites.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK