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26 April, 2000

Pinnipeds (seals) 2 Question 67: How many blowholes (nasal openings) do whales have? Continued from 4/25/00... Weddell Seals are the most southerly mammal. The adults grow to 3 meters in length and weigh from 400-500 kg. They dive to depths between 200 and 400m for fairly short periods of time (less than 15 min). They eat fish, cephalopods (squid and octopus), crustaceans including krill, isopods, and amphipods. Stones have been found in their stomachs, as they have in Crabeater and Leopard Seal stomachs also. Weddell Seals are solitary during the summer at the outer edge of the fast ice and inner areas of the pack ice. They depend on being able to find surface air access through cracks in the ice or holes kept open by the seals chewing on the ice. Pupping groups form on the fast ice in spring (anywhere from September to November depending on the latitude) with several females sharing a breathing hole and giving birth on the ice around it. The mother nurses the young for around 6 weeks, by which time the 15 kg birth weight has increased to 110 kg. She occasionally leaves the pup to feed. Southern Elephant Seals are the largest pinniped and are one of the largest mammals in the world excluding whales. Males can reach 4.5 meters and 4000 kg. Females are much smaller but still impressive at 2.8 m and 900 kg. They most likely feed deep in the water column. They have a visual pigment in their eyes which is found also in deep-water fishes and is thought to be an adaptation for detecting bioluminescence of deep-sea squids. They take prey similar to that of Sperm Whales which feed at great depths; and their close relative, the Northern Elephant Seal, is known to take prey found from 100-300 meters deep. The adults eat primarily cephalopods and some fish. The young seals may eat isopods as well for a short time after being weaned. Unlike the ice-breeding seal species, the Southern Elephant Seal and the other land-breeding species, the Fur Seal, are very group-oriented, hauling out in large numbers both during breeding season and at other times. In both Elephant and Fur Seal, the males stake out a territory where females will haul out to have their pups. Elephant Seals prefer sandy or shingle beach area, and male territorial battles usually involve nothing more than threats; little actual fighting takes place. Pups are born in September. Cows usually stay on the beach until the pups are weaned. Pups weigh around 46 kg at birth and quadruple their weight by the end of the three weeks their mothers nurse them. Elephant Seals do not breed until around age 7. In the non-breeding season they disperse and have been sighted up to 2000 km from their breeding grounds near Tasmania, New Zealand and South Africa. Fur Seals are the only eared seal living in polar waters. In addition to their external ear flaps they are distinguished from the phocid seals by having less blubber. Instead, they have a two-layer coat that gives them additional thermal insulation with its outer guard hairs and fine underfur. They are much more mobile than any of the other seals, using their strong jointed flippers as legs. Adult males are around 200 cm in length and weigh around 125-200kg. Females are smaller, weighing 50 kg and having a lenth of around 130 cm. They dive, mostly at night, to depths of 20-50 meters, eating mainly fish and krill. Their breeding colonies tend to be the same rocky shore areas year after year. Males defend their territories with vocal threats and fierce physical fighting that often leads to severe wounds. Pups are born near the start of November. After giving birth and feeding the pup for around a week, the female seals return to the sea to feed, then come back to feed their pups again, continuing this cycle for up to 110 days. At birth the pups weigh around 5.5 kg and gain around 1 kg a day. Little is known about the pelagic (open ocean) non-breeding life of these seals from May to October. A beautiful sunrise today brought almost everyone out on the dock to take pictures of the pink-streaked, cloud-patterned sky as well as of the Leopard Seal snoozing on a growler (small chunk of mostly-submerged glacial ice berg) just off the dock in Hero Inlet. Answer 66: Like baleen whales, both crabeater and leopard seals have a special adaptation that allows them to strain krill from water. In the case of the seals the premolar and molar teeth have elongated cusps, and, with the jaws closed, they fit together to make a sieve.


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