Albinistic common seals (Phoca vitulina) and melanistic grey seals (Halichoerus grypus) rehabilitated in the Netherlands

The Seal Rehabilitation and Research Centre (SRRC) in Pieterburen, The Netherlands, rehabilitates seals from the waters of the Wadden Sea, North Sea and Southwest Delta area. Incidental observations of albinism and melanism in common and grey seals are known from countries surrounding the North Sea. However, observations on colour aberrations have not been systematically recorded. To obtain the frequency of occurrence of these colour aberrations, we analysed data of all seals admitted to our centre over the past 38 years. In the period 1971-2008, 3000 common seals (Phoca vitulina) were rehabilitated, as well as 1200 grey seals (Halichoerus grypus). A total of five albinistic common seals and four melanistic grey seals were identified. This results in an estimated incidence of albinism in common seals of approximately 1/600, and of melanism in grey seals of approximately 1/300. The seals displayed normal behaviour, although in the albinistic animals, a photophobic reaction was observed in daylight.