Presence, Behavior, and Resighting Pattern of Transient Bottlenose Dolphins (Tursiops truncatus) in the Humboldt Current System off North-Central Chile

Biotic and abiotic factors determine presence and habitat use pattern of individuals within a population. In this study, presence, behavior, and resighting patterns of transient bottlenose dolphins (Tursiops truncatus) were evaluated in relation to upwelling and downwelling events in a marine reserve in North-Central Chile, between 2005 and 2009. The study period was divided into four phases according to wind direction and intensity: upwelling-favorable (UF), transition I (TI), convergence (Cv) or downwelling, and transition II (TII). Results show that transient bottlenose dolphins are an open population with low resighting rates. Highest occurrence and a largest number of transient dolphins were identified during 2009, probably due to an increase in prey availability. The most frequent behavior observed was traveling, followed by feeding and socializing. Traveling was mainly recorded in individuals seen only once and in years with low productivity. In contrast, feeding was observed in individuals seen two or more times, was similar among phases, and was more frequent in more-productive years. Social behavior was associated with the highest resighting rates. This study documents how transient bottlenose dolphins use the area based on their resighting patterns and suggests that periods of upwelling and downwelling modulate behavior displayed by these dolphins within the area.