Caspian seals (
Pusa caspica), one of the smallest members of the "true seal" family, are unique in that they are found exclusively in the brackish
Caspian SeaThe Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. It has a surface area of 371,000 square kilometres and a volume of 78,200 cubic kilometres...
. 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. In winter, and cooler parts of the spring and autumn season, these marine mammals populate the Northern Caspian.
Caspian seals (
Pusa caspica), one of the smallest members of the "true seal" family, are unique in that they are found exclusively in the brackish
Caspian SeaThe Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. It has a surface area of 371,000 square kilometres and a volume of 78,200 cubic kilometres...
. 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. In winter, and cooler parts of the spring and autumn season, these marine mammals populate the Northern Caspian. As the ice melts in the warmer season, they can be found on the mouths of the Volga and
UralThe Ural , known as Yaik before 1775, is a river flowing through Russia and Kazakhstan. It arises in the southern Ural Mountains and ends at the Caspian Sea. Its total length is 1,511 mi...
Rivers, as well as the southern latitudes of the Caspian where cooler waters can be found due to greater depth.
It is so-far unclear as to how these seals became isolated in the landlocked Caspian Sea. One of the most widely known hypotheses argues that the seals reached the Caspian during the
QuaternaryThe Quaternary period is the youngest of three periods of the Cenozoic era in the geologic time scale of the ICS. It follows after the Neogene period, spanning 2.588 +/- 0.005 million years ago to the present...
period from the north when continental ice sheets melted, and are descended from the
Ringed sealThe ringed seal , also known as the jar seal and as netsik or nattiq by the Inuit, is an earless seal inhabiting the northern coasts.-Description:...
.
Description
Adults are approximately 1.5 meters in length and weigh around 86 kilograms; males are generally larger and bulkier. Their dental formula is I 3/2, R 1/1, PC 6/5.
Caspian seals are shallow divers, with diving depths typically reaching 50 meters and lasting about a minute, although deeper and longer depths have been recorded. They are gregarious, spending most of their time in large colonies.
After an 11 month gestation period, the single pups are born in January and February. Similar to other ringed seals, these pups are born with white pelage and weigh about 5 kilograms. Their white coat is molted at around three weeks to a month. Sexual maturity is reached at 5 years for females, and about 6 or 7 years for males.
Prey and Predators
Caspian seals feed on cyprinids,
gobiesThe 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...
, and crustaceans. The seals may enter river
estuariesAn estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries are thus subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of...
to eat
carpCarp is a common name for various species of an oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. Some consider all cyprinid fishes carp, and the family Cyprinidae itself is often known as the carp family...
,
roachThe Common Roach is a freshwater and brackish water fish native to most of Europe and western Asia...
and pike-perch.
Sea eaglesA sea eagle is any of the birds of prey in the genus Haliaeetus in the bird of prey family Accipitridae....
are known to hunt these seals, which results in a high number of fatalities for the juveniles. They are also hunted by humans for subsistence and commerce. Due to the increasing industrial development in the surrounding region, pollutants and pesticides have entered the Caspian and caused significant habitat problems, weakened immune systems and contributed to disease outbreaks.
In a three week period in February 1978, wolves were responsible for the wanton killing of numerous seals near
AstrakhanAstrakhan is a major city in southern European Russia and the administrative center of Astrakhan Oblast. The city lies on the Volga River, close to where it discharges into the Caspian Sea. Population: 502,800 ; 504,501 ; 509,210 .-Medieval history:Astrakhan' is situated in the Volga Delta, rich...
. Between 17-40% of the seals in the area were estimated to have been killed, but not eaten.
Since the late 1990s, there have been several cases of many Caspian seals dying due to
canine distemperCanine distemper is a very serious viral disease that affects animals in the families Canidae, Mustelidae, Mephitidae, Hyaenidae, Ailuridae, Procyonidae, Pinnipedia, some Viverridae and Felidae...
virus.
A century ago there were an estimated 1.5 million seals; by the 1980s, there were about 400,000.
http://dsc.discovery.com/news/2007/05/01/caspianseals_ani.html?category=animals&guid=20070501160030
External links