Of the 80 known cetacean species, 49 are found in waters around Australia.
These include 38 species in the Par- vorder Odontoceti (toothed whales) and 11 species in the Parvorder Mysticeti (baleen whales) (Jackson and Groves 2015). Three species, all Odontocetes, are held in oceanariums in Australia: the Indo-Pacific bottle-nosed dolphin (Tursiops aduncus), the common bottle-nosed dolphin (T.
truncatus) and the Australian hump-backed dolphin (Sousa sahulensis). This chapter primarily deals with these species and the free-ranging species in the Australian region. This chapter, complemented by several other chapters and appendices within this volume presents advances in cetacean medicine since the publication of the first edition of Medicine of Australian Mammals. The medicine and pathology of Australian cetaceans is covered comprehensively in Blyde and Vogelnest (2008) and Ladds (2009); this chapter should be read alongside these texts.Australia has a vast coastline with a relatively small human population. In recent decades human populations, particularly along the coast, have increased dramatically. Industries such as mining, agriculture and oil and gas extraction have expanded, leading to contamination and degradation of the marine environment. Pollutant concentrations, including pesticides, herbicides and heavy metals, and marine debris are increasing in urbanised marine environments, affecting the marine fauna that inhabit them. Human activities such as shipping, fishing, recreation and waste disposal (particularly sewage) have also resulted in significant marine degradation. Climate change is altering the marine environment, affecting marine mammals, especially those that are geographically restricted (Meager and Limpus 2014). The emergence of infectious diseases such as morbillivirus, toxoplasmosis and lacaziosis in Australian cetaceans is likely related, at least in part, to this degradation, through increasing susceptibility and exposure to pathogens. Climate change and overfishing are having an effect on cetacean food resources, predisposing them to diseases associated with marine toxins as animals switch diets to less-preferred prey species.
Human activities that have direct effects on cetaceans, particularly the in-shore estuary inhabiting species, have increased. The incidence of entanglement in nets, fishing line and ropes (Fig. 46.1) and of boat strikes is increasing.