Pusa caspicaCaspian seal

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Geographic Range

Pusa caspica, Caspian seals, are one of the most numerous and widespread of northern pinnipeds. They are only found in the world’s largest inland body of saltwater, the Caspian Sea, which is located in a small part of the Paleartic region, between the countries of Russia, Azerbaijan, Iran, Turkmenistan, and Kazakhastan. Caspian seals migrate to different parts of the Caspian Sea during different seasons, however they never leave the landlocked Caspian Sea. From May to September most Caspian seals live in the southern part of the Caspian Sea. In autumn, they migrate north to the ice sheets for the birth of their newborn pups and breeding season. ("Seal Conservation Society", 2001; Ridgway and Harrison, 1981; Wikipedia, 2006)

There are various ideas to explain how Caspian seals began inhabiting the Caspian Sea. One theory is that they are direct descendants of ringed seals (Pusa hispida). During the Quaternary period, when there were glacier ice sheets, ringed seals migrated south. When the ice retreated seals were left isolated in the Caspian Sea. Others argue that Caspian seals originally occupied an inland area of the Paratethys Sea during the Miocene and Pliocene epochs. Other researchers argue that ringed seals are derived from Caspian seals and eventually migrated north to the Arctic. (Ridgway and Harrison, 1981; Wikipedia, 2006)

Habitat

Caspian seals live in the temperate region of the Caspian Sea on islands or fast ice sheets. This landlocked, saltwater sea is 100 ft (30.84 m) below sea level and at latitudes of 37 to 47 degrees north. Caspian seals can also be found in estuaries. The mouths of the Volga and Ural rivers are the most popular of these estuaries. ("Seal Conservation Society", 2001; "UNEP World Conservation", 2004; Reeves, et al., 2002; Ridgway and Harrison, 1981)

During winter months Caspian seals live in the north on ice caps. There, females give birth and nurse their young. A small portion of the population breeds farther south in the winter on islands such as Ogurchinsky, near the Turkmenistan coastline. These breeding areas tend to be in protected places like pressure ridges away from the wind and predators. Unlike their closest relatives, ringed seals (Pusa hispida), Caspian seals do not give birth in lairs (holes in snow drifts); this is said to maybe be an adaptation to ice that is not as stable as Arctic ice. During the spring and summer months, Caspian seals migrate south to live on sand banks or rocky areas, usually on islands and usually not on the main coastline. The southern part of the Caspian Sea has deeper water where seals may dive up to 50 meters. ("UNEP World Conservation", 2004; Reeves, et al., 2002; Ridgway and Harrison, 1981)

  • Average elevation
    -30.84 m
    -101.18 ft
  • Range depth
    50 (high) m
    164.04 (high) ft

Physical Description

When Caspian seals are born, they have a coat called a lanugo, made up of long white to silver gray fur. The lanugo helps keep pups warm until they develop blubber. Newborn pups are between 64 to 79 cm in length and weigh about 5 kg when born. After 2 to 3 weeks, the lanugo begins to shed and is replaced by dark gray hair; this process takes 6 to 8 weeks. It's possible that, when pups are weaned at a younger age, they may become smaller adults. ("Science and Conservation of Ice loving Seals", 2002; Reeves, et al., 2002; Ridgway and Harrison, 1981)

Adult Caspian seals are one of the smallest pinnipeds in the “true seal” family (Phocidae). Adult Caspian seals vary in size and appearance. Males grow to 1.5 meters in length, which is slightly larger than females, who reach 1.4 meters. Both males and females have grayish-yellow to dark gray fur coats with a lighter underbelly. Males tend to be darker with dark spots over the entire body, whereas females are lighter in color with lighter spots on the back and not on the belly. The spots of Caspian seals can also be encircled by light colored rings. Both males and females have relatively short flippers with moderate sized claws on their fore flippers and shorter, narrower claws on their hind flippers. Adult Caspian seals have a dental formula of I 3/2, R 1/1, and PC 6/5. ("Caspian Seal", 1984; Reeves, et al., 2002; Ridgway and Harrison, 1981)

The closest relatives of Caspian seals are ringed seals (Pusa hispida), the skulls of both are similar morphologically. However, unlike those of Caspian seals, the bodies of ringed seals are covered with light rings against a dark background. Both species are similar in size and have a relatively long narrow snout. These two species do not inhabit the same areas, being separated by 1600 km. (Reeves, et al., 2002; Ridgway and Harrison, 1981)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • Range mass
    50 to 86 kg
    110.13 to 189.43 lb
  • Average mass
    55 kg
    121.15 lb
  • Range length
    1.4 to 1.8 m
    4.59 to 5.91 ft
  • Average length
    1.45 m
    4.76 ft

Reproduction

Both male and female Caspian seals are monogamous. There seems to be no fighting for a mate among breeding seals. (Nowak, 1964; Reeves, et al., 2002)

In late autumn, Caspian seals migrate to the northern part of the Caspian Sea where the water is shallow and frozen. Caspian seals give birth in protected areas on ice sheets after a gestation period of about 11 months. There is no evidence to support this currently, but researchers believe that since there is a long gestation period, there is a delay in implantation of the egg. Annual pregnancy rates are normally between 40 to 70 percent, but are currently at an all time low of 30 percent. This maybe due to pollution. In late January to early February, each female seal gives birth to one pup. Female pups become sexually mature after 5 to 7 years, male pups become sexually mature after 6 to 7 years. Newborn pups are not fully grown for 8 to 10 years after they are born. Breeding begins a few weeks after the birth of last years’ pup, in late February to mid March. Breeding occurs after weaning of newborn pups but can begin while pups are still nursing. After the breeding season and molting in late April, the weather in the north starts to warm and the ice begins to melt. Caspian seals then migrate back to the southern part of the Caspian Sea. The southern part has deeper, colder waters where seals spend the summer months. ("Phoca caspica", 1990; Reeves, et al., 2002; Ridgway and Harrison, 1981)

  • Breeding interval
    Caspian seals breed once a year.
  • Breeding season
    Breeding occurs from late February to March.
  • Range number of offspring
    1 to 1
  • Range gestation period
    10 to 11 months
  • Range weaning age
    1 to 1 months
  • Range age at sexual or reproductive maturity (female)
    5 to 7 years
  • Range age at sexual or reproductive maturity (male)
    6 to 7 years

There is no available information about the parental care of Caspian seals, except that newborn pups are weaned after 4 to 5 weeks of lactation. Given that Caspian seals are asocial there may be no collaboration with other seals in raising newborn pups. In their closest relatives, ringed seals, as well as other seal species, males leave females soon after mating and do not help raise the newborn pups. Females will leave newborn pups to forage for short periods of time. (Reeves, et al., 2002; Ridgway and Harrison, 1981)

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

In the wild, Caspian seals live to be on average about 35 years old; however, some have been recorded to live 50 years. Males have relatively short lives, around 26 years. Caspian seals are not usually found in captivity except for a few zoos in Russia. There is no evidence of their life span in captivity. ("UNEP World Conservation", 2004; Reeves, et al., 2002)

  • Range lifespan
    Status: wild
    26 to 50 years
  • Average lifespan
    Status: wild
    35 years

Behavior

Caspian seals tend to live in large groups during the mating season in summer and winter months. At other times of the year, these seals are solitary. There is little else known about their behavior. (Reeves, et al., 2002; Wikipedia, 2006)

Caspian seals are shallow divers, typically diving 50 meters for about one minute, although scientists have recorded Caspian seals diving deeper and for longer periods of time. After foraging during a dive, they rest at the surface of the water. (Reeves, et al., 2002; Wikipedia, 2006)

Home Range

Home range sizes are unknown. ("Caspian Seal", 1984)

Communication and Perception

Little is known about communication in Caspian seals. They are solitary in winter months, in summer months they make aggressive snorts or use flipper waving to tell other seals to keep their distance. (Reeves, et al., 2002)

Food Habits

Caspian seals are primarily piscivorous. They eat a variety of foods depending on season and availability. Clupeonella (kilka) is the most abundant food source in the Caspian Sea, accounting for 70% of their diet. When Caspian seals inhabit shallow waters in the northern part of the sea (autumn and winter months), they prey mostly on sculpins, gobies, and crustaceans. While in the southern part of the Caspian Sea (deep waters), during the summer months, they eat herring, roach, carp, sprat, and smelt. When Caspian seals live in estuaries, they eat large amounts of the freshwater species Sander lucioperca. Other prey include shrimp, crab, silversides, and asp. ("Phoca caspica", 1990; "UNEP World Conservation", 2004; Reeves, et al., 2002; Wikipedia, 2006)

  • Animal Foods
  • fish
  • aquatic crustaceans

Predation

Besides humans, the two other predators of Caspian seals are sea eagles and wolves. Sea eagles snatch up newborn pups soon after they are born, during lactation their mortality rate is around 22%. In the northern part of the Caspian Sea, wolves will kill seals lying out on islands. (Reeves, et al., 2002)

Ecosystem Roles

Caspian seals are the only mammal found in the Caspian Sea, and they are near the top of the food chain. They eat many different types of fish and crustaceans. If seal populations decrease, the number of fish may increase. Seal population density may also affect the numbers of their two predators, wolves and eagles. ("Phoca caspica", 1990; Reeves, et al., 2002)

Economic Importance for Humans: Positive

For the past 200 years, humans living around the Caspian Sea have killed seals for their blubber and for the lanugo fur of newborn pups. Currently around 60,000 Caspian seal pups are caught annually for their fur. Some ecotourism is increasingly focusing on these animals, which involves taking ferries out to view them. ("Seal Conservation Society", 2001; "UNEP World Conservation", 2004; Nowak, 1964; Reeves, et al., 2002)

Hunting Caspian seals in the past has been intense. For example, between 1933 and 1940 an average of 160,000 seals were caught each year. In 1940, when the hunting of Caspian seals was first regulated, there was still an average of 50,000 to 60,000 caught each year. In 1970 restrictions were increased on the northern ice allowing only 20,000-25,000 pups to be killed. However, when the Soviet Union collapsed, these regulations were not enforced. In addition, the weak Soviet Union contributed to a large increase in illegal killing and poaching of Caspian seals. ("Seal Conservation Society", 2001; Reeves, et al., 2002)

  • Positive Impacts
  • food
  • body parts are source of valuable material
  • ecotourism

Economic Importance for Humans: Negative

Caspian seals do not negatively affect humans. They may take some fish, but these are not typically fish that are economically important.

Conservation Status

According to International Union for the Conservation of Nature (IUCN) Red list of Threatened Animals, Caspian seals are identified as vulnerable. This is for several reasons: loss of food by commercial fishing, toxic pollution, habitat destruction, human disturbance, disease, and commercial exploitation. In addition to a few regulations limiting the amount of Caspian seals caught each year, adult females are also protected during the breeding season. ("Science and Conservation of Ice loving Seals", 2002; "UNEP World Conservation", 2004; Nowak, 1964)

Other Comments

Caspian seals were previously known by the scientific name Phoca caspica.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Bonnie Easley-Appleyard (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

delayed implantation

in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

food

A substance that provides both nutrients and energy to a living thing.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

1984. Caspian Seal. Pp. 125 in D Macdonald, ed. The Encyclopedia of Mammals, Vol. 2, 2 Edition. New York: Equinox.Ltd.

1990. Phoca caspica. Pp. 220-238 in B Grimeks, ed. Grimeks Encyclopedia of Mammals, Vol. 5, 2 Edition. New Jersey: McGraw-Hill.

2002. "Science and Conservation of Ice loving Seals" (On-line). Caspian seal. Accessed March 10, 2006 at http://pagophilus.org/caspian.html.

2001. "Seal Conservation Society" (On-line). Caspian Seal. Accessed March 10, 2006 at http://www.pinnipeds.org/species/caspian.htm.

2004. "UNEP World Conservation" (On-line). Accessed March 10, 2006 at http://www.unep-wcmc.org/index.html?http://www.unep-wcmc.org/species/data/species_sheets/caspian.htm~main.

Anderson, H. 1969. The Biology of Marine Mammals. New York: Academic Press.

Cassini, M. 1999. The evolution of reproductive systems in pinnipeds. Behavioral Ecology, Volume 10/ number 5: 612-616.

Harwood, J. 2001. MARINE MAMMALS AND THEIR ENVIRONMENT IN THE TWENTY-FIRST CENTURY. Journal of Mammalogy, 82/3: 630–640..

Khuraskin, L., N. Zakharova. 2002. "Phoca (Pusa) caspica" (On-line). Accessed March 10, 2006 at http://www.caspianenvironment.org/biodb/eng/mammals/Phoca%20(Pusa)%20Caspica/main.htm.

Maclaren, I. 1966. Taxonomy of Harbor Seals of the Western North Pacific. Journal of Mammalogy, Vol 47/ Nu 3: 466-473.

Nowak, R. 1964. Walkers Mammals of the World. London: John Hopkins University Press.

Reeves, R., B. Stewart, P. Clapham, J. Powell. 2002. Guide to Marine Mammals of the World. New York: Chanticlear Press.

Ridgway, S., R. Harrison. 1981. Handbook of Marine Mammals. San Diego: Academic Press Limited.

Wikipedia, T. 2006. "Wikipedia" (On-line). Accessed March 19, 2006 at http://en.wikipedia.org/w/index.php?title=Caspian_Seal&oldid=42880722.