Skin disorders in free-ranging Chilean dolphins (Cephalorhynchus eutropia) from Biobío, Chile.

Skin disorders reports in cetaceans are increasing worldwide and may reflect individual or population health. This study describes the occurrence and distribution of skin disorders in Chilean dolphins Cephalorhynchus eutropia from Gulf of Arauco, Chile, based on photographic records collected during a summer 2024 expedition. A total of 685 photos were reviewed, with 39 meeting quality criteria and 16 showing identifiable skin lesions. Of the 37 dolphins photo-identified, 17 (45.95%) presented lesions. Tattoo skin disease (TSD) was diagnosed in 29.73% of individuals, with one animal showing signs of healing. Pale skin patches (PSP) and orange hues were also observed, with a prevalence of 10.81% and 5.41%, respectively. Lesions were primarily located on the thorax and lumbar regions and varied in size. This is the first report of TSD in Chilean dolphins from the Gulf of Arauco. Although the aetiology of PSP and orange hues remains uncertain, they may be associated with environmental factors such as salinity and diatom colonization. Given the conservation category of this endemic species, continuous monitoring of skin conditions and environmental parameters is recommended to understand the health implications and design conservation strategies.