Baikal seal
Baikal seal | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Carnivora |
Clade: | Pinnipedia |
Family: | Phocidae |
Genus: | Pusa |
Species: | P. sibirica
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Binomial name | |
Pusa sibirica Gmelin, 1788
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Baikal seal range | |
Synonyms | |
Phoca sibirica |
The Baikal seal, Lake Baikal seal or nerpa (Pusa sibirica) is a species of
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]
Distribution
The Baikal seal lives only in the waters of
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.
Abundance and trends
Since 2008, the Baikal seal has been listed as a
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.
The most serious future threat to the survival of the seal may be
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.
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.
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
Foraging
Their main food source is the
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]
References
- ^ . Retrieved 12 November 2021.
- ^ ISBN 0-375-41141-0.
- ^ a b c d e f g h "Baikal Seal (Phoca Sibirica)". Seal Conservation Society. Archived from the original on 6 October 2007. Retrieved 2007-09-27.
- ^ a b c d e f g h i "Baikal seal". baikal.ru. Retrieved 1 June 2017.
- ^ a b c d e f g h i j Pastukhov, Vladimir D. "The Face of Baikal – Nerpa". Baikal Web World. Archived from the original on 25 October 2007. Retrieved 2007-09-27.
- ^ a b c Schofield, James (27 July 2001). "Lake Baikal's Vanishing Nerpa Seal". The Moscow Times. Retrieved 2007-09-27.
- S2CID 30684638.
- .
- ^ Harrold, A. 2002. “Phoca Sibirica” (on-line), Animal Diversity Web. Accessed August 27, 2007.
- ^ "Mysterious Fish of Lake Baikal". Science First Hand. 30 September 2004. Retrieved 1 June 2017.
- PMID 33199633.
- .
- .
External links
- Peter Saundry. 2010. Baikal seal. Encyclopedia of Earth. topic editor: C. Michael Hogan; ed. in-chief: Cutler J. Cleveland. Washington, DC (Accessed May 21, 2010)
- Earth Island Institute. “The Lake Baikal Seal: Already Endangered” (on-line), Baikal Watch. (Accessed March 6, 2004; archive.org link added August 25, 2010.)