Prevalence and spatio-temporal variation of epidermal conditions, deformities and injuries in common bottlenose dolphins ( Tursiops truncatus ) in Welsh waters

Epidermal conditions, traumatic marks, deformities, and unusual body pigmentation were visually assessed on common bottlenose dolphins ( Tursiops truncatus ) using photo-identification and sightings data collected between 2007 and 2018 in Welsh waters. The goals of this study were to describe and categorize external body conditions, in particular, analyse the influence of age, sex, and distribution patterns on the mark prevalence, and assess the temporal and spatial patterns of lesions over time. During 222 boat-based trips, 287 individual dolphins were identified and almost all (99.3%) had skin marks, with individuals carrying between 1 and 12 different types. Linear, conspecific tooth-rake, dark fringe and abraded fin tip were the most prevalent mark types. The investigation of the influence of age, sex, and distribution patterns on skin lesion prevalence showed that adults had significantly higher prevalence compared to calves ( t 75 = 3.6, p = 0.001, μ A = 3.9, μ C+J = 2.6), males compared to females ( t 64 = 2.3, p = 0.03, μ F = 4.4, μ M = 5.6), whilst “transients” had a significantly higher number of different marks ( t 31 = 3.3, p = 0.001, “residents” = 3.6; “transients” = 5.9) compared to “residents” within the study area. Eighteen mark types were re-sighted over time. Despite a number of limitations which need to be taken into account, the minimum skin mark prevalence estimates produced in this study provide insights into the health status of common bottlenose dolphins and key evidence on local antagonistic, anthropogenic, infectious and parasitic pressures informing the conservation of this species in Welsh waters.