Factors determining whistle emission rate in bottlenose dolphins of Bocas del Toro, Panama.

Abstract

Dolphins of Bocas del Toro are known to change their communication signals when interacting with dolphin‐watching boats. In this study we examine the role of engine noise, calf presence, and behavior on the emission rate of whistles. Whistle emission rate was measured in groups where calves were and were not present and while interacting and not interacting with boats. A general higher whistle emission rate was shown when only the research boat was present and during social events, although whistle contours were not significantly different. Whistle rate was also slightly higher in groups with calves, particularly during social events. While in the presence of other boats, whistle emissions were higher during traveling events. A low whistle emission in the presence of other boats than the research boat (largely dolphin‐watching boats) may be the result of masking or a response to the engine noise during these encounters. In addition, groups with calves may be avoiding intrusive dolphin‐watching boats. Most groups with calves, for which whistle emission was higher during social events, were observed during encounters with the research boat (engine off). These results provide insights on some of the environmental and biological factors that may be influencing dolphin whistle emission.