Baikal Seal, Pusa sibirica
The Baikal seal (Pusa sibirica), also known as the nerpa or the Lake Baikal seal, is a true seal in the Phocidae family that is native to Lake Baikal located in Siberia. This species is one of three seals that reside solely in fresh water areas. It is not known exactly how these seals came to inhabit such an isolated area, but some experts assert that a sea-passage was formed that linked the Arctic Ocean and Lake Baikal.
The Baikal seal is one of the smallest of all true seal species, reaching an average body length of approximately four feet, with a weight between 150 and 330 pounds. Males are only slightly larger than females, and both sexes have dark grey dorsal fur, with yellowish grey fur on the underbelly. Young individuals bear white spots as they grow into adult fur, and older individuals appear brownish grey in color. Some adult individuals do not lose the adolescent spotting on their fur, but these are rare.
The breeding season for the Baikal seal occurs in the winter, shortly after the pups from the previous breeding season have been weaned. Females will construct dens under the ice, which males will spray them with urine to alert other males that the owner of the den has already bred. Each male may breed with a few females, but are not strictly territorial over each female. After delayed implantation and a pregnancy period of nine months, one or two pups are born in dens constructed within the ice. This species is one of two true seals that can birth twins, which will often remain close together after weaning. The den is typically up to sixteen feet in length before the pups are born, but after two days of age, the pups will expand the den by digging tunnels. It is thought that this occurs because the pups do not have a thick layer of blubber and need to stay active in order to keep warm.
Baikal seal pups are nursed for up to two and half months, longer than any other seal species. Mothers are often pregnant while still nursing pups from the previous year’s breeding season. The pups can increase their weight by five times between birth and weaning, after which time the mother will introduce them to solid foods.
The Baikal seal is typically solitary in nature, preferring to remain far apart during the warmer months of the year. Larger groupings of this species can be seen in the northern area of Lake Baikal, because the ice there stays frozen for longer periods. When the lake is mainly frozen, these seals will maintain a few breathing holes, but will remain under water until the ice begins to melt, when they will emerge onto the shore. During the winter, pregnant females are the only individuals that will haul out, with the rest of the population emerging closer to spring. During this period, both males and females will begin to molt. The seals rarely eat or move while molting, a common occurrence during hauling out, but many individuals will die due to overexposure to heat. Once the ice is melted, large groups of up to five hundred individuals will form on the shore or on ice floes.
The main diet of the Baikal seal consists of the golomyanka, a species found only in Lake Baikal. In one year, these seals can eat up to 64,000 tons of these fish. Feeding occurs mostly at night at depths of up to 330 feet, with dives lasting for up to twenty minutes, although the seals can remain under water for longer periods. Occasionally, these seals will consume small invertebrates or omul. In recent years, there has been a decrease in omul populations, causing some to assert that the Baikal seal eats more than previously thought. In reality, these seals aid the omul by consuming large amounts of its main competitor, the golomyanka. During the fall season, before the lake freezes over, the seals will move towards the shore to consume sculpin. These fish reside in silty areas, and once consumed, the silt will clean the seal’s intestines of any bacteria.
In 2007, the Baikal seal was listed as a lower risk species on many conservation lists, although it is thought that there could be a large decrease in their numbers in the near future. In 1994, the Russian government preformed a study that resulted in the count of 104,000 thousand individuals, but in 2000, Greenpeace recounted the seals and found them to number between 55,000 and 65,000 individuals. The main threats to these seals are probably hunting, poaching, and pollution.
There has always been a quota on the amount of Baikal seals that can be hunted, but in the past few centuries, this quota was raised many times. In the 1970’s, when the fur industry increased, counts were conducted that showed an increase in the seals population. In 2000, the quota was decreased from 6,000 individuals per year to 3,500 individuals. New practices, like taking pups from their dens and netting breathing holes, were created to more effectively kill a larger number of seals. It was found in one area that three to four thousand breathing holes were covered. One seal pelt can cost as much as 1,000 rubles, more than a hunter’s monthly salary.
There are eight designated wildlife patrol officers that each controls an area of 0.967 square miles. This makes it difficult to enforce hunting laws or insure that the quota is properly met. Some of the seals are not killed immediately, and will die later after escaping. These are not counted in the quota until after they are discovered. The government will need to better enforce the quota before hunting and poaching can decrease.
The threat of pollution to the Baikal seal includes the introduction of pesticides like DDT into the surrounding environment of Lake Baikal, and industrial waste that originates from nearby plants. It is thought that this waste was the cause of several disease outbreaks in 1997 and 1999.The waste entered into the ecosystem, infecting the seal’s food sources and caused them to have weak immune systems. The most common diseases caught include the plague and canine distemper, which have killed thousands of seals. The Baikal seal currently appears on the IUCN Red List with a conservation status of “Least Concern.”
Image Caption: Baikal seal. Credit: Uryah/Wikipedia (CC BY-SA 2.1 JP)