Skin and Mucosal Lesions of Indo‐Pacific Bottlenose ( <scp> <i>Tursiops aduncus</i> </scp> ) and Common Dolphins ( <scp> <i>Delphinus delphis</i> </scp> ) of South Australia, With a Focus on Pathology

ABSTRACT Skin lesions are valuable indicators of individual and population health in cetaceans. To understand the occurrence of skin and mucosal lesions among dolphins inhabiting South Australian waters, this study employs opportunistic sampling of deceased dolphins during 2021–2024. A total of 52 dolphins, comprising 23 Indo‐Pacific bottlenose dolphins ( Tursiops aduncus ) and 29 common dolphins ( Delphinus delphis ), underwent thorough macroscopic, microscopic, and ancillary diagnostics of identified lesions. Thirty‐three individuals displayed 115 skin and 12 mucosal lesions. The most common skin lesion sites were the head (23%–34%), peduncle (25%–26%), and lateral surfaces (17%–19%). A negative association was found between body condition and the number of infectious skin lesions in T. aduncus . Tattoo Skin Disease was identified in 13% of D. delphis skin lesions and 29% of T. aduncus skin lesions. Additional etiologies of skin lesions included bacteria (including Erysipelothrix rhusiopathiae , Mycobacterium marinum , Vibrio spp.), protozoa, physiological, and trauma‐related (propeller strike and shark bite). Opportunistic bacterial ulcerative dermatitis occurred predominantly in dolphins from the Adelaide Dolphin Sanctuary. Novel findings include the identification of herpesvirus in oral/genital papillomas, cutaneous lesions from an erysipelas‐infected animal, and M. marinum skin abscessation, not previously reported in free‐ranging Australian cetaceans. This study complements live‐animal observational studies and provides diagnostic insight into dolphin skin lesions, supporting their use as population and ecosystem health indicators.