Weddell Seal

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The Weddell Seal (Leptonychotes weddellii), a "true seal", is named after Sir James Weddell, commander of British sealing expeditions in the Weddell Sea. They occur in large numbers and inhabit the circumpolar region of the southern hemisphere, including Antarctica. It is estimated that there are approximately 800,000 individuals today. They can regularly be seen in the many seasonally ice-free islands along the Antarctic Peninsula. These pinnipeds are not thought to migrate, and any local movements are usually the result of changes in ice conditions.

[edit] Behavior and ecology

Weddell Seals are known for their very deep dives -- which may reach some 700 meters. They can also hold their breath for approximately 80 minutes. Such deep dives involve foraging sessions, as well as searching for cracks in the ice sheets that can lead to new breathing holes. The seals can remain submerged for such long periods of time because of high concentrations of myoglobin in the muscles.

Depending on the latitude they inhabit, these marine mammals give birth from early September through November. Those living at lower latitude give birth earlier in that range. They are not very social out of water, even avoiding physical contact at most times. Copulation has only been observed to occur underwater, where the female is often bitten in the neck by her partner. Young Weddell seals have gray pelage for the first 3 to 4 weeks; later they turn to a darker color. Play fighting is very common for these animals as they grow. The pups reach maturity at 3 years of age. The colour of the adults is very dark brown, lighter ventrally, and mottled with large darker and lighter patches, those on the belly being silvery white. Adult males usually bear scars, most of them around the hind flippers and genital region. Weddell seals have a shorter lifespan than most other pinnipeds. On average, Weddell seals live for 20 years, compared to an average life expectancy of 40 years for most other seals. This is because Weddell seals winter under the Antarctic sea ice adjacent to continental Antarctica where they are required to constantly grind away at the ice which forms at the edges of their breathing holes. This has the effect of wearing down their teeth over time. Once a Weddell seal's teeth have worn down to a certain level, the seal is unable to eat and eventually starves to death.

The Weddell seal lives further south than any other mammal, inhabiting the waters of McMurdo Sound, 800 miles from the South Pole. These relatively meek animals are usually found in large groups on ice attached to the continent and can be easily approached by humans.

[edit] Protection

The Weddell Seal is protected by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals.

[edit] General information

In the 1900s the Weddell seal (being a very calm animal) allowed people to come up to them, but many of the people were branders branding them with a unique branding iron and giving them wounds that could never heal because of the small layer of blubber surrounding them. Seals are well adapted to the cold climate,with their big round bodies,layers of blubber(fat)and small flippers. they were once hunted for their valuable fur but now are protected by law.

[edit] References

• Seal Specialist Group (1996). Leptonychotes weddellii. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006.

1. OBIS-SEAMAP
2. ADW: Leptonychotes weddellii
3. Adaptions of Diving Mammals
4. Audio recording from Macaulay Library at Cornell Lab of Ornithology

[edit] Further reading

• Zapol, W. M. (1987) Diving Adaptations of the Weddell Seal. Scientific American. 256(6):100-105.de:Weddellrobbe

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