THE GREY SEAL ( HALICHOERUS GRY PUS FAB.) IN THE OUTER HEBRIDES IN OCTOBER 1961

• Published in: Proceedings of the Zoological Society of London
• Main Author: BOYD, J. MORTON
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1963
• Subjects: Rona; common seal; Phoca vitulina
• Online Access: http://dx.doi.org/10.1111/j.1469-7998.1963.tb01620.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1469-7998.1963.tb01620.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1963.tb01620.x; https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1963.tb01620.x

There are two resident seals in the Outer Hebrides: the grey seal Halichoerus grypus on the exposed coasts, and the common seal Phoca vitulina on the sheltered ones. This paper describes the first exhaustive survey of the breeding status of the grey seal in the archipelago, conducted from land, sea and air in the autumn of 1961. Expeditions visited Shillay and North Rona, and aerial photographs were obtained of all the other islands except Stockay, Flodday and St. Kilda, for which information was obtained from other reliable sources. The data obtained concerned the number of pups present at one day in the breeding season. The birth‐rate curves for Shillay (1955) and North Rona (1959) were used with these data to give indices of the number of pups produced by each colony in 1961. Separate assessments were made for Stockay, Flodday and St. Kilda. Possible sources of error are discussed. The following are the indices for number of pups in 1961: North Rona, 2,600; Gasker, 1,094; Shillay, 150; Haskeir, 113; St. Kilda, 100; Causamul, 84; Coppay, 80; Stockay, 50; Kearstay, 20; Deasker, 17; Flodday, 50. For the Outer Hebrides as a whole the index is 4,378 or approx. 4,400. The history of the grey seal in the Outer Hebrides is reviewed. An increase in stocks is evident throughout the last century subsequent to the evacuation of North Rona in 1844. This is attributed to the gradual human depopulation of the area, with remote islands such as North Rona, St. Kilda and the Monachs becoming deserted by man and subsequently colonized by seals. The increase began well before 1914 when the Grey Seals Protection Act was passed, but this has since preserved stocks.