Welsh Journals

THE GREY SEAL IN WALES SHEILA S. ANDERSON INTRODUCTION Although Grey seals, Halichoerus grypus (Fabricius 1791) on the Welsh coast form only a small fraction of the total British population, many of the early observations on Grey seal biology were made on the Pembrokeshire breeding groups (Davies 1949 & 1953, Matthews 1950 & 1955, Lockley 1966b, Johnson 1959 & 1961). Apart from concentrations of animals on the islands of Ramsey and Skomer, small breeding groups in caves and on beaches are scattered along the Pembrokeshire and Cardigan coast and around the Lleyn Peninsula and Anglesey. Accurate counting of the number of pups born is consequently difficult. Johnson, quoted in Smith (1966), estimated that pup production in Pembrokeshire was between 250 and 500, and Lockley (1966) suggested 350. Hewer (1974) estimated that 2000 Grey seals occur in the south-west area, which includes Wales, Cornwall, Isles of Scilly and southern Ireland. Several authors (Coulson & Hickling 1964; Lockley 1966a, b; Bonner 1972) record differences in the timing of the Grey seal breeding season around Great Britain, and suggest that these differences provide evidence for reproductive isolation. The Grey seals of the south-west are thought to be the earliest breeding group, with the peak of pupping occuring around the end of September. Summers (1974) found that the Cornish seals pupped from mid September onwards, but that the Scillies group were earlier, with most pups born by the beginning of October. In a recent review of British seal stocks, Bonner (1976) includes a summary of the status of the Grey seal in Wales. The present report sets out in detail the distribution and population estimates for this species in Wales, and describes the field survey and estimating techniques used in a major survey in autumn 1974. METHODS survey techniques All surveys were made trom boats (Mark 111 Zodiac inflatables) between 20 September and 11 October 1974. Landings were made on all beaches and in caves where pups were seen or where adults were found offshore. The caves were investigated either from the boats or by swimmers in wetsuits. Limitations of time allowed only one visit to be made to each area, except for Skomer Island where the Warden, J. E. Davis, collected data throughout the pupping season. For the purposes of the survey the Welsh coast was divided into ten areas (Fig. 1). Pups were counted and classified into five age classes, so that the timing of the pupping season could be defined. The age classes were described by Boyd, Lockie & Hewer (1962), except that the age class duration was modified from seven to five days (SRD unpublished data). Although pup counting was the main priority, adults and juveniles were counted and some pups were tagged to investigate dispersal from the breeding areas.