Pusa caspica

Geographic Range

Phoca 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.

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.

• Biogeographic Regions
• palearctic palearctic
  • native native

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.

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.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine

• Aquatic Biomes
• coastal coastal

• Other Habitat Features
• estuarine estuarine

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.

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.

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently

Reproduction

Both male and female Caspian seals are monogamous. There seems to be no fighting for a mate among breeding seals.

• Mating System
• monogamous monogamous

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous
• delayed implantation delayed implantation
• post-partum estrous

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.

• Parental Investment
• precocial 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.

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.

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.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• migratory migratory
• solitary solitary

Home Range

Home range sizes are unknown.

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.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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 Stizostedion lucioperca . Other prey include shrimp, crab, silversides, and asp.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• 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.

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.

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.

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.

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

Other Comments

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

Additional Links

Encyclopedia of Life

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.

References

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