Reproductive behaviour of the Grey seal (Halichoerus grypus) on Sable Island, Nova Scotia

摘要: We describe an unusual mating system, observed in a land-breeding colony of Grey seal, Halichoerus grypus, the western Atlantic. Males and females begin to visit breeding beach about week before season begins, but none stay ashore for long until first pup is born. The cows are gregarious, probably return same part give birth from one year next, tend remain general vicinity site during their two half sojourn ashore. Within these limits, however, they quite mobile, size, location composition temporary aggregations which form vary day next. become thinner more sedentary as oestrus approaches, otherwise no overt signs receptivity. males do not defend territories, nor dominance hierarchies. Instead, compete tenure, right within shifting population females. Tenured bulls directly test receptivity nearby time time, continually manoeuvre ways maximize chances being next either or likely so near future. Bulls fail establish themselves amongst try intercept leaving sea at end season, reproductive success, estimated several ways, significantly lower than that with tenure. The system would be adaptive seals breed on pack ice, it unique pinnipeds. If, some circumstantial evidence suggests, were originally pack-ice breeders, persistence such raises interesting questions plasticity behaviour.