Changes in surfacing patterns of bottlenose dolphins in response to boat traffic

Recent growth in commercial whale and dolphin watching has raised the question of how cetaceans are affected by boat traffic. Many studies in this field looked at effects on baleen whales (review in Richardson et al. 1995), while only a few, e.g., Au and Perryman (l982), Kruse (1991) and Polacheck and Thorpe (1990) have studied influences on smaller odontocetes. The dominant behavioural reactions of cetaceans reported in these studies were an increase in swimming speed, spatial avoidance, and changes in diving behaviour. All these are short-term reactions which may disrupt the ongoing activities of the animals. Such disruptions could cause longer-term changes in the behaviour and status of a population through avoidance of certain areas or an increase in mortality (Thompson 1992, Richardson et al. 1995).