Skin lesions and physical deformities in bottlenose dolphins in the Moray Firth: population prevalence and age-sex differences

Bottlenose dolphins resident in the Moray Firth, NE Scotland, display a variety of skin lesions and physical deformities which appear to be signs of disease, the cause of which is unknown. The population is isolated and small (around 130 individuals) and it is important to determine the severity of this problem to establish if there is cause for concern. Assessing the health of free-ranging marine mammals is difficult. We used photographs of individuals, taken over a four year period, to provide a full and systematic description of the types of lesions and deformities present and to document the prevalence of each type. Overall, 95% of dolphins sampled showed one or more types of lesion on the back or dorsal fin; 61% had three or more types and 5% had six or seven types. Six percent of animals displayed deformities. Lesions on adult females and calves covered significantly greater areas of skin than on adult males or sub-adults. The results show that visible disease is a prominent feature of this population and is, therefore, a cause for concern. The next step is to establish whether this is a natural feature or is anthropogenically induced and the findings are discussed in this context.