Do Calves Matter?: The Effect of Number of Boats and Mode of Approach on the Behavioral and Acoustic Responses of Cetacean Groups Groups with Calves

Abstract

The effect of whale watching on cetacean populations has been of popular concern since the whale watching industry increased dramatically during the past decade. Whales and dolphins show behavior and acoustic reactions to boat approaches that could potentially lead to a disruption of vital activities, and thus, vital rates of the populations. Unfortunately, the long term population consequences of behavior responses are yet to be understood. There are several factors that could influence how cetaceans respond to whale watching including the time of exposure, the activity budget, and the presence of calves. Calves have always been considered more vulnerable to interactions with whalewatching boats and their presence in a group could elicit different behavioral and acoustic responses from those of groups without calves. In this review I analyze the importance of including presence of calves as a factor influencing variation in responses to boat interactions by reviewing the evidence for differences in behavioral and acoustic responses. In many cases, studies are based on the average of behavioral responses and very few studies divide data by group composition (e.g. groups with mother-calf pairs). In the cases where groups’ composition was considered, mother-calf pairs showed more 2 avoidance behaviors and more vulnerability to boat interactions. The information of acoustic responses of mothers and calves is limited, particularly for baleen whale species. However, vocalization rates vary among groups with and without calves, which represent a source of variation in the data for acoustic responses of a population to vessel noise. For these reasons, I recommend that the presence of calves be included as an important factor for future assessments of whale-watching impacts on behavior and acoustic responses. Adding this factor will refine the data and management can be targeted to more vulnerable groups.