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Marine Ecology Progress Series

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MEPS 205:283-290 (2000)  -  doi:10.3354/meps205283

Changing occurrence of epidermal lesions in wild bottlenose dolphins

Ben Wilson1,2,*, Kate Grellier1, Philip S. Hammond 2, Gary Brown3,**, Paul M. Thompson1

1Department of Zoology, University of Aberdeen, Lighthouse Field Station, Cromarty, Ross-shire IV11 8YJ, United Kingdom
2Sea Mammal Research Unit, Gatty Marine Laboratory, University of St. Andrews, Fife KY16 8LB, United Kingdom
3Department of Mathematical Sciences, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom
*Address for correspondence: Sea Mammal Research Unit, Gatty Marine Laboratory, University of St. Andrews, Fife KY16 8LB, United Kingdom. E-mail: **Present address: Office for National Statistics, 1 Drummond Gate, London SW1V 2QQ, United Kingdom

ABSTRACT: There are increasing concerns that human activities promote the development of natural diseases in aquatic organisms. Of these, diseases concerning small cetaceans have received increasing attention. Most studies have focused on dead animals and provided information on pathogens, contaminant exposure and probable causes of death. However, our understanding of diseases in living populations, particularly with respect to prevalence during the lives of individuals, and for whole populations in different years, remains limited. This study was designed to provide such information on epidermal lesions (abnormalities not directly attributable to physical trauma that may indicate disease) in a wild population of bottlenose dolphins Tursiops truncatus. An 8 yr time series of photographs of 82 free-ranging dolphins from NE Scotland was used to investigate the occurrence and dynamics of epidermal lesions in 7 age classes of young dolphins (from their 1st to their 7th summer of life) and for an adult group. Lesions were found at high prevalence (90 to 100%) in both young and adult dolphins, with 1st-summer calves having the lowest levels. Lesions of different appearance showed 2 patterns of occurrence, either being restricted to young individuals or becoming more common with age. When severity was compared between calves (in their 2nd summer of life) born in 8 different years, a significant decline over time was observed (p < 0.005). Comparison of this change with environmental and anthropogenic factors may help identify which factors may be promoting the ubiquitous epidermal lesions in these dolphins.

KEY WORDS: Disease · Cetaceans · Photo-identification · Pollution · North Sea

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