Acoustic response of Hawaiian spinner dolphins to human disturbance
Hawaiian spinner dolphins display predictable daily behavior, using shallow bays to rest during the daytime. The frequency and intensity of the interactions between humans and dolphins in these bays has prompted concern for the animals. All previous research on the dolphins' response to human activity has been conducted visually. In contrast, here we evaluate whether dolphins acoustically respond to human activity. Previous research found that the dolphins were silent during rest and that acoustic activity matched their general behavioral state. Therefore, we expected to see higher dolphin whistle activity before and after peak resting time and low activity to indicate rest. The daily pattern of dolphin whistle activity in two of the four bays matched what we expected. However, in two bays we did not find a drop in dolphin whistle activity. With regards to the acoustic response of the animals to human activity, we found relationships between the number of vessels and dolphin acoustic activity in a bay with dolphin focused activities but not in the bay with the most vessel activity. Our results suggest that the key factor is not the sheer presence or magnitude of human activities but rather the directed interactions and the dolphin focused activities that elicit a response.
