Marine Science @ Otago - Marta Guerra

How do dolphins react to boats and underwater noise?

 

 In the last two decades there has been a rapid growth in nature tourism, including boat-based whale and dolphin watching. As a consequence, coastal cetaceans have been increasingly exposed to boats and noise. Doubtful Sound (Fiordland, New Zealand) is home to a small resident population of 62 bottlenose dolphins (Tursiops truncatus), and is also a hotspot for tourism, with boat cruises running year round in the fiord. 

As part of her MSc thesis, Marta Guerra spent a year making acoustic recordings and observing the dolphins' behaviour to understand how they are affected by the presence and noise of tour boats.

 The research showed that dolphin groups with mother−calf pairs were less coordinated and more dispersed in the presence of tour boats, while groups without calves were not affected. These groups also became more vocal when boats were close and while moving away, presumably to re-establish group structure. Dolphins also responded to boat noise by altering the pitch and duration of their whistles.

These findings suggest that elevated boat noise affects communication, and that groups with calves are particularly sensitive to boat presence and noise.

 Due to the population being endangered and having a history of low calf survival, these findings have relevant implications for the management of boat tourism in Doubtful Sound.