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Life is not by any means easy for Adélie penguins. Even by Antarctic standards, they have so much stacked against them - from the brown skuas, the large sea birds that attack their eggs and young on shore, to the swift and terrible leopard seals that await them in the sea.
Their chances of survival are bound up with how they group on land and the manner in which they put to sea. Both survival gambits depend on the one thing penguins have in abundance - numbers. The Adélie breed in huge colonies, within which are subgroups, each slightly withdrawn from the next.
Breeding in a group is definitely better than breeding alone, since a group affords warmth and some protection from attacks by skuas. Skuas are reluctant to enter the center of a breeding colony to raid nests for eggs or chicks, so by far the best breeding place is at the center of a group.
The larger groups are generally the most successful because the exposed outer fringe of each group is smaller in relation to the number of birds that are protected by it. Being part of a large group also contributes to survival when it comes to feeding. Penguins must go to sea in order to feed and, as they are only too aware of the patrolling leopard seals that await them offshore, they always depart from the colony in a crowd.
Nervously the penguins congregate on the ice at the edge of the water, anxiously examining each wave trough and crest for the sleek form of a leopard seal. Even a suggestion of a dark head bobbing in the water will send them all back up the beach in a panic, to regroup and approach again.
As soon as one has jumped - or been pushed - the rest follow in rapid succession, swimming as fast as they can beyond the leopard seal area of activity. The more penguins there are entering the water at any one time, the smaller an individual penguin chance of becoming the next victim.
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