The effects of tour boats on the behavior of bottlenose dolphins (Tursiops truncatus) in Walvis Bay, Namibia

Abstract

Cetacean watching has increased in recent years, being whales and dolphins the focus of these tourism activities. Several studies worldwide have suggested that tour boat activities have effects on cetacean’s behavior. Here, we studied the population of common bottlenose dolphins (Tursiops truncatus) inhabiting Walvis Bay (Namibia), in order to analyze the effect of tour boat activities on the dolphins’ behavior. Boat-based behavioral surveys were carried out by the Namibian Dolphin Project organization from 2009 to 2016. Temporal variation in dolphins’ behavior over seasons (winter and summer) and years was also analyzed. Our results showed that bottlenose dolphins mainly reduced their resting and surface feeding behaviors under the presence of tour boats, while milling and socializing behaviors were increased. This suggests that the population is reacting to tour boat presence by balancing their activity budget and energetic demands. The dolphins also exhibited a seasonal and annual effect on their behavioral budget, proposing that tour boat activity may have influenced this species, as dolphins have not completely habituated to this disturbance. Small and dispersed groups of dolphins observed under the presence of tour boats suggested that dolphins in Walvis Bay actively avoided boat interactions. However, further studies are necessary in order to document long-term effects in areas where tourism activity is experiencing an increase. Also, future conservation and management plans towards achieving a more ecological and economic sustainability of the cetacean-watching activity would be needed.