First insights into the effects of swim-with-dolphin tourism on the behavior, response, and group structure of southern Australian bottlenose dolphins

摘要

This study was conducted to determine the impact of cetacean tourism on southern Australian bottlenose dolphins (Tursiops australis) inhabiting Adelaide coastal waters in Gulf of St. Vincent, South Australia. The effect of vessel approaches and the presence of swimmers in the water on the behaviour, response and cohesiveness of bottlenose dolphin groups were analysed. The variations in these parameters were also examined depending on dolphin group size and age-class composition. Observations of bottlenose dolphins involved in interactions with swimmers were conducted during the autumn season and between March and May 2010. Observations were only conducted in calm sea conditions. The behavioral sampling was conducted in three stages: before swim (dolphins have been spotted but no swimmers are in the water); during swim (swimmers are in the water with the dolphins); and after swim (swimmers are back on board of the vessel, but dolphins are still visible). A total of 63.72 h survey time was spent in the field over 19 days of study. Results revealed that the behavioral budget for traveling, milling, and feeding differed significantly among the three sampling stages. The time budget for traveling decreased from before impact to during impact as well as from before impact to after impact. The time budget for milling increased from before impact to during impact and decreased from before impact to after impact. Comparing the time budget of feeding before impact and after impact, there was a significant increase in the time the dolphins spent feeding after impact. Response was different between large and small groups, wherein large groups were more likely to approach the swimmers rather than the boat while small groups were more likely to approach the boat and not the swimmers. Calf presence did not influence the response of the dolphins. Results indicated that bottlenose dolphins in Adelaide's coastal waters changed their behaviour significantly when they were exposed to swim-with-dolphin tourism activities. The shifts in the behavioral budgets showed that even after the swimmers exited the water, the behavioral budgets did not return to the same levels they were before the interaction. This suggested that the interaction with the tourist vessels and swimmers altered the dolphins' behaviour not only during the time of approach, but continued after the boat had left. There were no significant difference in group cohesiveness among the different sampling stages. It is recommended that the legislation for marine mammal watching in South Australia should restrict the number of daily tours and operators to minimize impacts on the dolphins. A restriction to one operator per site with a limit of one tour per day for Adelaide coastal waters is suggested until more is known about the impacts of swim-with-dolphin tourism in this area.