Caspian Seal
Encyclopedia
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. 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 Ural
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 Quaternary
period from the north when continental ice sheets melted, and are descended from the Ringed seal
.
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.
, and crustaceans. The seals may enter river estuaries
to eat carp
, roach
and pike-perch.
Sea eagles
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 Astrakhan
. 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 distemper
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
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...
family, are unique in that they are found exclusively in the brackish Caspian Sea
Caspian Sea
The 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. The sea has a surface area of and a volume of...
. 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 Ural
Ural River
The Ural or Jayıq/Zhayyq , 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 making it the third longest river in Europe after the Volga and the Danube...
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 Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows 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 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...
.
Description
Adults are approximately 1.5 metres (4.9 ft) in length and weigh around 86 kilograms (189.6 lb); 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, gobiesGoby
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...
, and crustaceans. The seals may enter river estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
to eat carp
Carp
Carp are various species of oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes, Siluriformes and Gymnotiformes to create the superorder Ostariophysi, since these groups have certain...
, roach
Rutilus
Rutilus is a genus of fishes in the family Cyprinidae, commonly called roaches. Locally, the name "roach" without any further qualifiers is also used for particular species, particularly the Common Roach Rutilus (Latin for "shining, red, golden, auburn") is a genus of fishes in the family...
and pike-perch.
Sea eagles
Sea eagle (bird)
A 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 Astrakhan
Astrakhan
Astrakhan is a major city in southern European Russia and the administrative center of Astrakhan Oblast. The city lies on the left bank of the Volga River, close to where it discharges into the Caspian Sea at an altitude of below the sea level. Population:...
. 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 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...
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
- Caspian seal factsheet at pinnipeds.org
- "Caspian Seal under threat of extinction", BaztabBaztabBaztab is an Iranian, Persian language, Tehran-based news website. The English service of this site has published since January 2007. Although Baztab is an anti-reformist website, it sometimes criticizes Mahmoud Ahmadinejad's government's policies and mostly unveils corruption cases inside the...
newspaper. Persian article.