Bottlenose dolphins increase breathing synchrony in response to boat traffic

To minimize potential impacts of boat traffic on the behavior of cetaceans it is important to assess short-term behavioral responses to boats and interpret the long-term consequences of these. Anecdotal descriptions of synchronous behavior in cetaceans are particularly frequent with reports of individuals within schools surfacing to breathe in a coordinated fashion being common. However, quantitative descriptions are rare. This study begins by quantifying synchronous breathing patterns of bottlenose dolphins off northern Scotland. We investigate possible functions of synchrony such as feeding patterns and presence of calves. We then test whether the presence of boat traffic in an area used intensively by dolphins affects their breathing synchrony. Although the majority of dolphin schools observed showed random breathing patterns, 30.5 % of schools showed synchronous breathing. There was no variation in this behavior with respect to identifiable feeding activities. However, synchrony was significantly negatively related to the presence of calves in the school (chi(2) = 7.17, df = 1, P = 0.007) and significantly positively related to the presence of boat traffic in the study area (chi(2) = 13.85, df = 1, P = 0.0002). Such consistent short-term behavioral responses by dolphins may potentially accumulate to produce longer-term consequences both for individuals and the whole population.