Pathology of the skeleton of Indo-Pacific bottlenose dolphins Tursiops aduncus: a comparison of adjacent gulfs in South Australia.

Studies of skeletal pathology of marine mammals can contribute to conservation measures, yet few have focused on causative factors. Museums hold vast collections of skeletons relevant to this knowledge gap. Indo-Pacific bottlenose dolphin Tursiops aduncus carcasses (n = 162) were collected from Gulf St Vincent (GSV) and Spencer Gulf (SG), South Australia (SA), between 1988 and 2013, and post-mortem examinations were carried out. After preparing skeletons, their gross pathology was classified into 4 categories: lytic lesions, degenerative lesions, fractures and malformations. Comparisons were made between gulfs based on pathology type, relative age, period of collection and cause of death (anthropogenic vs. non-anthropogenic). Pathology prevalence (76%) was higher than reported in other studies but observed pathologies were similar. More than one pathology was observed in 88% of dolphins that had pathology. Vertebrae were often the site of pathology. Prevalence of lesions were: fractures (82%), lytic lesions (75%) including spondylo-osteomyelitis and osteomyelitis, degenerative lesions (57%) including spondylosis deformans, and malformations (17%). Prevalence of pathology increased with dolphin relative age, and GSV dolphins had more pathology than those in SG. In SG, anthropogenic cases had more pathology than non-anthropogenic cases, and dolphins collected after 2000 had more degenerative lesions than those collected before 2000. There were more malformations in SG dolphins than those from GSV, although this was not statistically significant. In one anomalous case, an individual was found with 5 detached transverse processes on 4 lumbar vertebrae. Heavy metal toxicity reported for T. aduncus from SG may be related to the malformations reported in this study.