A PRELIMINARY ACCOUNT OF A COLONY OF GREY SEALS HALICHOERUS GRYPUS (FAB.) IN THE SOUTHERN INNER HEBRIDES

Abstract

SUMMARY A breeding colony of grey seals is centred on Eileaii Ghaoidmeal and Eileaii nan Ron. south of Oronsay. Argyll. Breeding on a very limited scale also takes place on the neighbouring islets and a few pups are born on the beaches of Colonsay. A very tentative figure of 350–400 pups each year is suggested for the whole colony. Seventy or more seals (of both sexes) may haul out on Eilean nan Ron alone, in August. The first birth is estimated at about 1st September and there were well over 100 pups (possibly 120–130) by the end of the month. No statistical evidence has yet been collected for October. The breeding beaches are separated from the open sea by an erosion platform crossed by channels and covered only for about four hours at high water. After the pups are born the cows pass to and from the sea along the channels but occasionally cross the kelp‐covered platform. During mid‐September a relatively large collection of bulls (40 +) hauls out on the skerries between Eilean nan Ron and Oronsay. All ages are present. There could not be observed any formal contests but the very large bulls tend to haul out separately as on Shillay. The numbers decreased rather suddenly, leaving only the older bulls. With the onset of pupping on Eilean nan Ron, the remaining bulls established territory near the breeding beaches in chequer‐board formation on the kelp‐covered platform. The positions first chosen are those most favourable for the interception of cows along the channels. The method of establishment and maintenance of territory by the bulls is described in detail. The progressive change in the behaviour of the cows and bulls culminating in mating is described. Cows appear to be ready to mate about fourteen days after parturition. In general the behaviour of both cows and bulls shows resemblances both to that seen in Pembrokeshire and, to a less extent, to that seen in the Hebrides. The presence of the erosion platform largely dictates the details of behaviour.