MATING BEHAVIOUR OF THE SEAL PHOCA VITULINA IN SHETLAND

Abstract

SUMMARY The pupping season of Phoca vitulina in Shetland is approximately 14th June to 5th July. Preceding the pupping season there is a period of excited erotic rolling behaviour among “pairs”. We have not seen this lead to coition nor have we seen it renewed in the immediate post‐lactation period by which time the seals have already begun to moult. Another rolling period commences in the first week of September and at this season it often leads to coition by moult‐completed seals. Mating finishes in the first week of October. The blowing of bubble streams is introduced into the rolling sequence during this autumn period. Rolling and bubble blowing are described A Table is given comparing the pupping and mating seasons of Phoca vitulina in Shetland with these seasons for the species in other parts of its range We have seen coition only on or close to the bottom of the sea in water of two to four fathoms and in the shallows immediately behind the breakers Rough water was avoided by mating seals. No sexual behaviour was seen ashore. No change of partners by rolling “pairs” of Phoca vitulina was seen but we have witnessed this, instigated by either sex, among rolling “pairs” of Halichoerus grypus. The possibility of the existence of a spring mating season is discussed. Counts are given of this Shetland Common Seal population to the north of Fitful Head. It has remained fairly constant at some 400 animals over the period 1954 to 1956 though many pups of up to six weeks old are slaughtered annually for their pelts.