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the Legacy continues…………………….
Gregory R. Mann, Ph.D. {ret.}

Crabeater Seal

“Lobodon carcinophaga”

Contrary to their common name, Crabeater Seals do not live up to their name, they do not feed primarily on crabs. These fascinating seals measure 2.2-2.6 meters in length and weigh 200-300 kilograms. Males and females are generally close in size with females typically slightly heavier. After the molting season, the back fur of the Crabeater Seal is dark brown fading to blond on its belly. These seals also have dark brown markings along the back and sides. Their flippers are very dark brown. The fur lightens throughout the year becoming completely blond in summer just before molting. Crabeater’s have a long snout and slender body. They inhabit the southern ocean and surrounding islands as well as South America, Australia, South Africa, Tasmania and New Zealand in winter. Because they live in remote, harsh environments, the exact population size of this species is unknown. Crabeaters probably got their name because of a mistake by the early sealers who went down to the Antarctic. They actually eat Krill, the staple diet of much of Antarctica’s bird and mammal population. Original estimates place the population at approximately 15 million, however it is now thought that the population is much smaller. Crabeater Seals migrate seasonally according to the movement of the pack ice. Crabeater Seals have distinctive and complex teeth. Each tooth has tubercles or bony protuberances, with spaces between them. The upper and lower jaws fit together so that when mouth is closed, the teeth and tubercles can strain krill. As mentioned previously, krill not crab is the primary food source for Crabeater Seals. They feed by swimming through schools of krill with their mouth open, sieving the water out using their sophisticated teeth. When they migrate outside the Antarctic, Crabeater Seals are thought to feed on other invertebrates as well as small fishes. They feed primarily at night typically all night long, hauling out on the ice to rest during the day. They are preyed on by Killer Whales and Leopard Seals. To deflect an attack, the Crabeater Seal will bare its teeth and snort or hiss when approached. They also tend to roll over to avoid being tackled by their predators.

Crabeater Seals are typically solitary animals, however they are also known to gather into aggregations of about 1,000 animals. They dive to feed on krill at night. They are known to dive for long periods of time up to 16 hours for feeding, traveling or migrating and exploring. The dives range between 10 meters for traveling dives, 30 meters for food and slightly deeper for exploratory dives. These seals have been known to use breathing holes in the ice created by Weddell Seals and in some cases may chase juvenile Weddell Seals away from their breathing holes. At the end of the summer when the ice begins to freeze, Crabeater Seals begin to travel north. Some Crabeaters have been known to become disoriented traveling south on the pack ice instead of north hundreds of kilometers inland. These are mostly juveniles and they usually die as a result of their misdirection. Those that travel north are bound for the islands of Oceania, Australia, South America and even South Africa. They are a highly mobile and fast pinniped that can travel up to 25 kph. When Crabeater Seals travel at this speed, they lift and swing their head from side to side moving their fore-flippers across the ice to navigate with their hind flippers elevated behind them to avoid drag.

Crabeater Seals are thought to reproduce in Antarctica on the pack ice during the early Spring months between October and December. Unlike other seal species, they tend to mate on the ice rather than in the water. In September following an 11-month gestation period, females give birth to a single pup on an ice floe. Pups are born about 1.2 meters in length and weigh between 20-30 kilograms and gain weight while nursing at a rate of about 4.2 grams per day. The mother and her pup stay in close contact for the duration of the nursing period, which lasts about 3 weeks. A male Crabeater Seal usually not the father, will join the female just before or just after she gives birth to protect the mother and her pup. Soon after weaning, females are ready to breed again and although her protective male defends her from the aggression of other males, he is typically aggressive toward the female during the nursing period. Crabeater Seals reach sexual maturity between 3 and 4 years of age. Females have successful pregnancies when they are between 5 and 25 years old.

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