DISPERSION AND SITE FIDELITY OF BREEDING FEMALE GREY SEALS (HALICHOERUS-GRYPUS) ON NORTH-RONA, SCOTLAND

Female grey seals (Halichoerus grypus) formed breeding aggregations on the island of North Rona, Scotland. Aggregations of females were asso ciated particularly with gullies leading from the sea, leaving large a reas of available space unoccupied. Changes in the degree of aggregati on of females during the breeding season were similar in 1987, 1988 an d 1989. Pronounced aggregations occurred in the early and late parts o f each breeding season. Of 67 breeding females marked in 1985, 62 (93% ) returned to N. Rona to breed in at least one season up to 1989, but 18 (27%) were present in all five years. Females came ashore up to 14 days before giving birth and 82% were observed first in the vicinity o f their subsequent pupping site. Between 1985 and 1989, marked females which returned were faithful to their previous pupping sites, even wh en the previous pup had died. There was no evidence of a gradual chang e in the location of individual pupping sites over time. This pupping site fidelity may generate aggregations whose location, timing and com position is predictable.