Baikal seal

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Baikal seal
Nerpa (Pusa sibirica) (3635255975).jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Phocidae
Genus: Pusa
Species:
P. sibirica
Binomial name
Pusa sibirica
Gmelin, 1788
Baikal Seal area.png
Baikal seal range
Synonyms

Phoca sibirica

The Baikal seal, Lake Baikal seal or nerpa (Pusa sibirica) is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seals and the only exclusively freshwater pinniped species. [2] A subpopulation of inland harbour seals living in the Hudson Bay region of Quebec, Canada, (Lacs des Loups Marins harbour seals), as well as the Saimaa ringed seal and the Ladoga seal (both ringed seal subspecies), are also found in fresh water, but these seals are part of species that also have marine populations. [2]

Contents

The most recent population estimates are 80,000 to 100,000 animals, roughly equaling the expected carrying capacity of the lake. [1] At present, the species is not considered threatened. [1]

Description

The Baikal seal is one of the smallest true seals. Adults typically grow to 1.1–1.4 m (3 ft 7 in – 4 ft 7 in) in length [1] with a body mass from 63 to 70 kg (139 to 154 lb). [3] The maximum reported size is 1.65 m (5 ft 5 in) in length and 130 kg (290 lb) in weight. [4] There are significant annual variations in the weight, with lowest weight in the spring and highest weight, about 38–42% more, in the fall. [5] The animals show very little sexual dimorphism; males are only slightly larger than females. [3] They have a uniform, steely-grey coat on their backs and fur with a yellowish tinge on their abdomens. As the coat weathers, it becomes brownish. [5] When born, the pups weigh 3–3.5 kg (6.6–7.7 lb) and are about 70 cm (2 ft 4 in) long. [1] They have coats of white, silky, natal fur. This fur is quickly shed and exchanged for a darker coat, much like that of adults. Rarely, Baikal seals can be found with spotted coats. [3]

A young seal Baikal-seal 4747-pho.jpg
A young seal

Distribution

Baikal seal in the Baikal museum Baikal seal 3.jpg
Baikal seal in the Baikal museum

The Baikal seal lives only in the waters of Lake Baikal. [6] It is something of a mystery how Baikal seals came to live there in the first place. The skull structure of the Baikal seal suggests it is closely related to the Caspian seal. In addition, the morphological structures in both species suggest they are descended from Arctic ringed seals. [7] They may have swum up rivers and streams or possibly Lake Baikal was linked to the ocean at some point through a large body of water, such as the Paratethys Sea, West Siberian Glacial Lake or West Siberian Plain, formed in a previous ice age. The seals are estimated to have inhabited Lake Baikal for some two million years. [8]

The areas of the lake in which the Baikal seals reside change depending on the season, as well as other environmental factors. They are solitary animals for the majority of the year, sometimes living kilometres away from other Baikal seals. In general, a higher concentration of Baikal seals is found in the northern parts of the lake, because the longer winter keeps the ice frozen longer, which is preferable for pupping. [5] However, in recent years, migrations to the southern half of the lake have occurred, possibly to evade hunters. [3] 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 nearby seals. When the ice begins to melt, Baikal seals tend to keep to the shoreline.

A Baikal seal mascot at the Nerpa Festival in Irkutsk, Baikal region, Russia Nerpa festival.JPG
A Baikal seal mascot at the Nerpa Festival in Irkutsk, Baikal region, Russia
Group of Baikal seals hauling out on a rock around Ushkany Islands: Barguzinsky district, Buryatia Iz zhizni baikal'skoi nerpy bliz Ushkan'ikh ostrovov 03.jpg
Group of Baikal seals hauling out on a rock around Ushkany Islands: Barguzinsky district, Buryatia

Since 2008, the Baikal seal has been listed as a Least Concern species on the IUCN Red List. [1] This means that they are not currently threatened or endangered. In 1994, the Russian government estimated that they numbered 104,000. In 2000, Greenpeace performed its own count and found an estimated 55,000 to 65,000 seals. [6] The most recent estimates are 80,000–100,000 animals, roughly equaling the carrying capacity of the lake. [1]

In the last century, the kill quota for hunting Baikal seals was raised several times, most notably after the fur industry boomed in the late 1970s and when official counts began indicating more Baikal seals were present than previously known. [5] The quota in 1999, 6,000, was lowered in 2000 to 3,500, which was still nearly 5% of the population if the Greenpeace count is correct. [3] In 2013–2014, the hunting quota was set at 2,500. [1] In addition, new techniques, such as netting breathing holes and seal dens to catch pups, have been introduced. In 2001, a prime seal pelt would bring 1,000 rubles at market. [6] In 2004–2006, about 2,000 seals were killed per year according to official Russian statistics, but in the same period another 1,500–4,000 are thought to have died annually due to drowning in fishing gear, poaching, and the like. [1] In 2012–2013, it was estimated that 2,300–2,800 were hunted per year (combined legal hunting and poaching). [1] Some groups have pressured for higher hunting quotas. [1]

Another problem at Lake Baikal is the introduction of pollutants into the ecosystem. Pesticides such as DDT and hexachlorocyclohexane, as well as industrial waste, mainly from the Baikalisk pulp and paper plant, are thought to have exacerbated several disease epidemics among Baikal seal populations. The chemicals are speculated to concentrate up the food chain and weaken the Baikal seal's immune system, making them susceptible to diseases such as canine distemper and the plague, which was the cause of a serious Baikal seal epidemic that resulted in the deaths of 5,000–6,500 animals in 1987–1988. [1] [3] Small numbers died as recently as 2000, but the reason for their deaths is unclear. [3] Canine distemper is still present in the Baikal seal population, but has not caused mass deaths since the earlier outbreaks. [1] In general, levels of DDT and non-ortho PCB have declined in the lake from the 1990s, levels of mono-ortho PCB are unchanged, and the level of perfluorochemicals have increased. [1] Industrialization of the area near Lake Baikal is increasing and future monitoring is necessary. At present, Baikal seals show lower levels of contaminants than seals of Europe and North America, but higher than those in the Arctic. [1]

The most serious future threat to the survival of the seal may be global warming, which has the potential to seriously affect a closed cold-water ecosystem such as that of Lake Baikal. [1]

The only known natural predator of adult Baikal seals is the brown bear, but this is not believed to occur frequently. [1] 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. [4]

Reproduction and growth

Female Baikal seals reach sexual maturity at 3–6 years of age, whereas males achieve it around 4–7 years. [3] 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 haul out during the winter. The males tend to stay in the water, under the ice, all winter. 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. [5] Very rarely, triplets or quadruplets have been recorded. [4] 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 lactating while pregnant.

Baikal seals are slightly polygamous and slightly territorial, although not particularly defensive of their territory. Males mate with around three 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 digs 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 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. [1] 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 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 haul themselves out and begin to moult their 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 often die of overheating, males especially, from lying on the ice too long in the sun. [5] 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, [5] although the females are presumed to be fertile only until they are around 30. [9]

Foraging

Their main food source is the golomyanka, a cottoid oilfish found only in Lake Baikal. Baikal seals eat more than half of the annual produced biomass of golomyanka, some 64,000 tons. [5] In the winter and spring, it is estimated that more than 90% of its food consists of golomyankas. [4] [10] The remaining food sources for this seal are various other fish species, especially Cottocomephorus (about 7% of the diet during the winter and spring) and Kessler's sculpin (about 0.3% of the diet in the winter and spring), but it may also take some invertebrates such as Epischura baikalensis , gammarids and molluscs. [4] During the autumn the Baikal seal eats 50–67% fewer golomyankas than in the winter and spring, but significantly more Cottocomephorus, Kessler's sculpins and stone sculpins. [4] A total of 29 fish species have been recorded in the diet. [1] They feed mainly during twilight and at night, when golomyankas occur in depths as shallow as 10–25 m (33–82 ft). [1] [4] During the day, golomyankas are typically found deeper than 100 m (330 ft). [1] Baikal seals can dive up to depths of 400 m (1,300 ft) [4] and stay underwater for more than 40 minutes. [1] Most dives last less than 10 minutes and generally only 2–4 minutes. [1] Baikal seals have two litres 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. According to a 2020 paper, Baikal seals also seek food through the use of filter-feeding on amphipods within Lake Baikal. [11] Baikal seals have specialized teeth that allow the seals to expel water while feeding, allowing them to gather large amounts of amphipods while swimming.

According to a 2004 paper on the foraging tactics of Baikal seals, [12] during the summer nights these seals are known to have different foraging strategies during night time and during day time. During the day, these seals use visual clues to search for their prey, which is mainly fish, while during the night they use tactile clues to hunt crustaceans. Since it is brighter during the day, the seals are able to see much better in order to hunt for the fish. Since there is no light at night, they have to hunt with tactile cues. The crustaceans they hunt at night have a diel migration, so they come up into shallower waters during the night, and swim to deeper waters during the day to escape predators. [13] These seals were observed to dive deeper during dawn and dusk in order to get to these crustaceans as they were swimming shallower and deeper, respectively.

The Baikal seal has been blamed for drops in omul numbers, but this is not the case. It is estimated that omul only comprises about 0.1% of its diet. [4] 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. [5]

Baikal seals have one unusual foraging habit. In early autumn, before the entire lake freezes over, they migrate to bays and coves and hunt Kessler's sculpin, a fish that lives in silty areas and, as a result, usually contains grit and silt in its digestive system. This grit scours the seals' gastrointestinal tracts and expels parasites. [5]

Related Research Articles

<span class="mw-page-title-main">Lake Baikal</span> Freshwater rift lake in Russia

Lake Baikal is a large rift lake in Russia. It is situated in southern Siberia, between the federal subjects of Irkutsk Oblast to the northwest and the Republic of Buryatia to the southeast.

<span class="mw-page-title-main">Pinniped</span> Taxonomic group of semi-aquatic mammals

Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage. Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.

<span class="mw-page-title-main">Ringed seal</span> Species of carnivore

The ringed seal is an earless seal inhabiting the Arctic and sub-Arctic regions. The ringed seal is a relatively small seal, rarely greater than 1.5 m in length, with a distinctive patterning of dark spots surrounded by light gray rings, hence its common name. It is the most abundant and wide-ranging ice seal in the Northern Hemisphere, ranging throughout the Arctic Ocean, into the Bering Sea and Okhotsk Sea as far south as the northern coast of Japan in the Pacific and throughout the North Atlantic coasts of Greenland and Scandinavia as far south as Newfoundland, and including two freshwater subspecies in northern Europe. Ringed seals are one of the primary prey of polar bears and killer whales, and have long been a component of the diet of indigenous people of the Arctic.

<span class="mw-page-title-main">Grey seal</span> Species of carnivore

The grey seal is a large seal of the family Phocidae, which are commonly referred to as "true seals" or "earless seals". The only species classified in the genus Halichoerus, it is found on both shores of the North Atlantic Ocean. In Latin, Halichoerus grypus means "hook-nosed sea pig". Its name is spelled gray seal in the US; it is also known as Atlantic seal and the horsehead seal.

<span class="mw-page-title-main">Leopard seal</span> Macropredatory species of Antarctic seal

The leopard seal, also referred to as the sea leopard, is the second largest species of seal in the Antarctic. Its only natural predator is the orca. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "thin-clawed".

<span class="mw-page-title-main">Hooded seal</span> Species of carnivore

The hooded seal is a large phocid found only in the central and western North Atlantic, ranging from Svalbard in the east to the Gulf of St. Lawrence in the west. The seals are typically silver-grey or white in color, with black spots that vary in size covering most of the body. Hooded seal pups are known as "blue-backs" because their coats are blue-grey on the back with whitish bellies. This coat is shed after 14 months of age when the pups molt. It is the only species in the genus Cystophora.

<span class="mw-page-title-main">Harp seal</span> Species of mammal

The harp seal, also known as Saddleback Seal or Greenland Seal, is a species of earless seal, or true seal, native to the northernmost Atlantic Ocean and Arctic Ocean. Originally in the genus Phoca with a number of other species, it was reclassified into the monotypic genus Pagophilus in 1844. In Greek, its scientific name translates to "ice-lover from Greenland," and its taxonomic synonym, Phoca groenlandica translates to "Greenlandic seal." This is the only species in the genus Pagophilus.

<i>Phoca</i> Genus of carnivores

Phoca is a genus of the earless seals, within the family Phocidae. It now contains just two species, the common seal and the spotted seal. Several species formerly listed under this genus have been split into the genera Pusa, Pagophilus, and Histriophoca. Until recently, Phoca largha has been considered a subspecies of Phoca vitulina but now is considered its own species. For this reason, the fossil history of the genus is unclear, and it has formerly been used as wastebasket taxon for a number of fossils of uncertain affinity.

<span class="mw-page-title-main">Weddell seal</span> Species of mammal

The Weddell seal is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica. The Weddell seal was discovered and named in the 1820s during expeditions led by British sealing captain James Weddell to the area of the Southern Ocean now known as the Weddell Sea. The life history of this species is well documented since it occupies fast ice environments close to the Antarctic continent and often adjacent to Antarctic bases. It is the only species in the genus Leptonychotes.

<span class="mw-page-title-main">Caspian seal</span> Species of seal endemic to the Caspian Sea

The Caspian seal is one of the smallest members of the earless seal family and unique in that it is found exclusively in the brackish Caspian Sea. It lives along the shorelines, but also on the many rocky islands and floating blocks of ice that dot the Caspian Sea. In winter and cooler parts of the spring and autumn season, it populates the northern Caspian coastline. As the ice melts in the summer and warmer parts of the spring and autumn season, it also occurs in the deltas of the Volga and Ural Rivers, as well as the southern latitudes of the Caspian where the water is cooler due to greater depth.

<span class="mw-page-title-main">Ribbon seal</span> Species of mammal

The ribbon seal is a medium-sized pinniped from the true seal family (Phocidae). A seasonally ice-bound species, it is found in the Arctic and Subarctic regions of the North Pacific Ocean, notably in the Bering Sea and Sea of Okhotsk. It is distinguished by its striking coloration, with two wide white strips and two white circles against dark brown or black fur.

<span class="mw-page-title-main">Saimaa ringed seal</span> Freshwater seal found in Finland

The Saimaa ringed seal is a subspecies and glacial relict of ringed seal. They are among the most endangered seals in the world, having a total population of only about 400 individuals. The only existing population of these seals is found in Lake Saimaa, Finland. They have lived in complete isolation from other ringed seal species for around 9,500 years and have diverged into a morphologically and ecologically different subspecies of ringed seal. 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 Ladoga seal and the Baikal seal, is one of the few living freshwater seals.

<i>Comephorus</i> Genus of fishes

Comephorus, known as the golomyankas or Baikal oilfish, are a genus comprising two species of peculiar, sculpin fishes endemic to Lake Baikal in Russia. Comephorus is the only genus in the subfamily Comephorinae. Golomyankas are pelagic fishes and the main food source for the Baikal seal.

The Ladoga ringed seal is a freshwater subspecies of the ringed seal found entirely in Lake Ladoga in northwestern Russia. This pinniped was isolated in freshwater lakes and separated from the Arctic ringed seal as a result of the isostatic rebound of the region following the end of the Weichselian Glaciation.

<i>Cottocomephorus</i> Genus of fishes in lake Baikal

Cottocomephorus is a genus of freshwater ray-finned fishes belonging to the family Cottidae, the typical sculpins. This genus is endemic to Lake Baikal and its surrounding tributaries in Russia. They have relatively large pectoral fins and reach up to 22 cm in total length. They are an important food for the Baikal seal, during the winter second only to the golomyankas.

The stone sculpin is a species of cottoid fish endemic to Russia, where it is found in Lake Baikal and surrounding tributaries as well as the Gramninskie Lakes, Lake Verkhnaya Agata and the Enisei River and various lakes in Tuva. This species is the only recognized member of its genus.

Procottus jeittelesii, the red sculpin or red Baikal sculpin, is a species of ray-finned fish belonging to the family Cottidae, the typical sculpins. This species is endemic to Lake Baikal in Russia. It is a freshwater fish that dwells under stones or in holes in the mud at a depth range of 0 to 800 m. It is often found at around 100 m (330 ft), and is most abundant during the autumn and winter. From the late winter to the spring it breeds at depths of 5 to 30 m. It can reach a maximum length of 18 cm (7.1 in), but typically is 10–12 cm (3.9–4.7 in). It has a red spotted or banded pattern on a light background. The red sculpin resembles two of its close relatives, the smaller P. gurwici and the larger P. major.

The bighead sculpin is a species of sculpin fish that is endemic to the Lake Baikal watershed in Siberia, Russia. It typically lives on rocky bottoms, often in places with sponges, at depths of 5 to 70 m (16–230 ft), but can occur as deep as 120 m (390 ft). Its colour varies from grayish to brownish or greenish depending on the bottom type. It can reach up to 22 cm (8.7 in) in length, but most are 13–16 cm (5.1–6.3 in). It feeds on a wide range of smaller animals such as young fish, insect larvae, amphipods, molluscs and oligochaetes. Breeding is in the spring where the female lays 618 to 1622 eggs, which are guarded by the male.

<span class="mw-page-title-main">Baikal yellowfin</span> Species of fish

The Baikal yellowfin, also known as the yellow-finned sculpin or yellow-wing sculpin, is a species of freshwater ray-finned fish belonging to the family Cottidae, the typical sculpins. This species is endemic to Lake Baikal and its tributaries in Siberia, Russia. It is most common in the southern part of the lake and lives from near the shore to a depth of 300 m (980 ft).

<span class="mw-page-title-main">Arctic ringed seal</span> Subspecies of carnivore

The Arctic ringed seal is a subspecies of ringed seals. Arctic ringed seals inhabit the Arctic Ocean, and are the most abundant and wide-ranging seal in the Northern Hemisphere. The ringed seal species is the smallest true seal, and gets its name from a distinctive patterning of light spots on dark grey colored fur. The ringed seal is commonly preyed upon by Polar bears, Arctic foxes, and Killer whales. Population estimates and survival rates are unknown, but average life expectancy is 15-28 years. Ringed seals have long been a component of the diet of indigenous people of the Arctic. Arctic ringed seals have been listed as threatened on the Endangered Species Act since 2012, and increasingly face loss of their habitat due to shrinking ice and snow cover.

References

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