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Page 2 - Breeding Behaviour of the Grey Seal off the Coast of Cape Breton

Published by Ronald Caplan on 1972/10/31 (4915 reads)
 

Breeding Behaviour of the Grey Seal off the Coast of Cape Breton taken from three articles by Austin uaraeron, Mammalogist, Senior Professor of Biology, Xavier College A colony of Grey seals (Halichoerus grypus) located on the Basque Islands (rocky islets off Point Michaud at longitude 61"~3egrees W. and latitude 45 degrees N.) has been kept under observation by the writer for varying periods since February 1966, and the data secured have provided virtually the only detailed information on the breeding behavior of this pinniped in the western Atlantic. That so little should be known about this species in North America is understandable since the total population does not exceed 10,000, there are only four known major land- based breeding colonies and pupping occurs in mid-winter when weather conditions make detailed observations almost impossible. In North America the Grey seal ranges from northern Labrador to Massachusetts, with the largest concentrations occurring in the Gulf of St Lawrence and along the Atlantic Coast of Nova Scotia. The four major land-based breeding colonies are: Deadman Island in the Magdalen Island Archipelago, Araet Island on the north coast of Nova Scotia, Sable Island and the Basque Islands where the present studies were undertaken. Less than 100 pups are born each year on Deadman and Amet, about 300 on Sable, 200 on the Basque Islands and an estimated 800 on the ice floes in the southern part of the Gulf of St Lawrence. Physical Characteristics and Life History The grey seal is a relatively large species with the full-grown males averaging close to 8 feet in total length and the females about 6 1/2 feet. Adult males are usually a plain dark grey, although some are mottled like the females. The females vary much more in color, but the throat and underparts are almost always a very pale grey and the medium brownish-grey coat is usually mottled with dark patches. Some females are a pale sandy brown. Older males have a "Roman nose" and there are extensive folds in the neck region, the latter characteristic distinguishing them from the younger bulls. The nose of the females is straight but rather long, a fea? ture which distinguishes them from the harbor seals (Phoca vitulina), with which they might be confused when the fur is wet.. The grey seal is one of those pinnipeds in which whelping occurs almost exclusively on land, usually on small remote islands and islets. At the beginning of the breed? ing season the adult bulls invade these islands and establish territories; at this time or shortly thereafter the cows come ashore and bear their pups within these territories. The cows "belong" to the bull in whose territory they happen to whelp and, according to British biologists, the bull shows no possessiveness towards his cows. This may not be entirely true among the grey seals in the western Atlantic. About 2 weeks after the birth of the single pup, mating occurs, so that the gesta? tion period is of 11 1/2 months duration. Delayed implantation occurs in this spe? cies as in other species of seals. When the pups are about a month old, the cows forsake them and return to the sea. The pups survive for some time thereafter on their reserve fat and eventually take to the water where they feed on tiny crusta? ceans and molluscs. The fluffy, white natal hair is shed when the pup is about 2 weeks old and is replaced by a pale grey coat. Territorial Behavior We will deal here with the seals of the islet called "Green" of the Basque Island group. The visible part of Green Island was divided between two bulls, one occupy? ing the southern end of the island. This bull is hereafter referred to as "bull A"

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