Does size really matter? How synchrony and size affect the dynamic of aggression between two sympatric species of dolphin in the Bahamas

Abstract

Bottlenose (Tursiops truncatus) and spotted ( Stenella frontalis) dolphins are sympatric species, resident to Little Bahama Bank, Bahamas. A unique, dynamic methodology quantified how interspecific aggression changed over time in terms of the individuals participating, context, and behaviors used. The timing of human observation relative to the onset of aggression did not result in differences in the proportion of behaviors observed. Highly intense behaviors were used most often. The synchronous state of spotted dolphin groups, not the presence alone, was a crucial factor in determining the onset and progression of aggression. When synchronous, spotted dolphins successfully dominated the larger bottlenose dolphins. Two levels of dominance were observed. Within a single encounter (“encounter level”), one species did dominate the other. When all aggressive encounters were considered collectively over the long term (“gross level”), one species did not dominate the other. The combination of contextual factors best determined the dynamic of interspecific aggression