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Piedras Blancas Elephant Seal EsealCam

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The Catastrophic Molt

From mid-March to mid-September, elephant seals are present on the beaches to grow new skin and hair and shed the old – to molt. Early in this period they share the beaches with the weaned pups which have not yet left for sea and the final weeks of the period they share with the juveniles who arrive for the fall haul-out. The adult females and the juveniles are the first to appear with their number reaching a maximum near the first of May and all departing by the first of July. The sub-adult and adult males begin to arrive in early May and are gone by early September. Each molting seal stays in the rookery for approximately one month.

The seals come to the rookery to molt rather than grow new skin and hair continuously as we do because growing skin requires circulating blood just inside the skin – outside their insulating blubber. With an internal body temperature near 100°F (38 C), and ocean water around 40°F (4 C), growing skin at sea would entail enormous energy loss. A measure of how serious that would be is that the seals travel thousands of miles over several weeks and fast on the beach for a month to avoid paying that price.

While in the rookery during this period, as at all other times, they fast – no food or water for the duration of their stay. Fasting necessitates a quiet life, lots of sleeping, not much moving around. The young males, however, do use this time as an opportunity to joust with each other, playfully developing skills that are vital to them as adults. Much of this sparring takes place in the tide pool areas just off shore at times determined more by tide than sun.


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