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A visual health assessment of a resident community of bottlenose dolphins in the Strait of Gibraltar

This paper is available in a repository.
This paper is available in a repository.

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Abstract

The bottlenose dolphin (Tursiops truncatus) is the cetacean species most commonly encountered in the Strait of Gibraltar. A community of about 300 T. truncatus resides year round in the central and deeper part of the Strait. It is exposed to stressful anthropogenic factors including a very high maritime traffic and commercial whale watching activities. In an attempt to assess the health of this community we thoroughly examined the left upper body of 334 dolphins for evidence of skin lesions, physical deformations and other conditions using 13,763 images taken for photo-identification studies in 2004-2007. Emaciation was not observed. Deformation of the dorsal fin associated with a very large scar was seen in an adult female. Tattoo skin disease (TSD) was detected in 4,5% of the dolphins. Prevalence was significantly (χ 2 = 6,62, df = 1, P = 0,01) higher in juveniles (12,5%, n= 40) than in adults (3,4%, n= 290). None of the four calves were affected by TSD. This holo-endemic epidemiological pattern is typical of the disease in healthy populations of odontocetes. Other cutaneous disorders included orange blotches (n= 1), pale dermatitis (n= 2), punctiform marks (n= 3), expansive annular skin lesions (n= 1), nodules (n= 3) and patchy depigmentation (n=1). The occurrence of pale dermatitis and expansive annular disease may be indicative of a deteriorating coastal water environment and should be further investigated.