The Influence of Species and Context on Human-Dolphin Interactions

Deirdre Breen Yeater


Anthropogenic activities pose a threat to marine mammals around the world. Cetaceans that use coastal waters are at particular risk for potential disturbances caused by vessel traffic and human swimmers. Although many cetacean species are found near the coast of Utila, Honduras, little is known about their behavior or the effects of anthropogenic activities on their behavior. Whether the presence of boats and human swimmers led to short-term changes in dolphin behavior was investigated for three commonly sighted species of dolphins; rough-toothed ( Steno bredanensis ), spinner ( Stenalla longirostris ), and bottlenose (Tursiops truncatus ). The dolphins' behavioral activities, with and without other boats present (in addition to the research vessel), were compared using individual behavioral events and behavior states. In addition, all occurrences of dolphin behaviors in response to human swimmers entering the water were recorded. Varying activity levels of humans in the water (e.g., floating vs. chasing) led to different responses by the dolphins. The results suggest that the behavior of the three species of dolphins differed when humans were present. Rough-toothed dolphins were the species that were most likely to encircle and orient towards human swimmers in the water. Spinner and bottlenose dolphins were likely to interact with moving boats (e.g., bowriding with the research vessel). Some interactions between humans and dolphins seemed non-aversive (e.g., dolphins sometimes approached human swimmers).