Influence of environmental variables, small-scale fisheries and vessel traffic on the distribution and behavior of bottlenose dolphins in a tropical lagoon.

Abstract

The distribution of marine predators is influenced by a variety of natural and, in some cases, anthropogenic environmental factors. In particular, the optimal foraging theory predicts that micro-habitat selection should be the result of a trade-off between prey availability, energy expenditure, and predation risk. In addition, the risk-disturbance hypothesis suggests that anthropogenic disturbance may be perceived by animals in the same way as predation risk. Habitat selection may also be locally influenced by individual behavior and physiological state (defining functional habitats): variation in their needs should affect their optimal trade-off. We tested these hypotheses in a population of bottlenose dolphins living in a tropical lagoon using a habitat modeling approach. Bottlenose dolphins were predominantly distributed within the lagoon, with a preference for the vicinity of fringing and inner reefs (with lower predation risk than the outer reef), and were located in areas of high fish productivity, consistent with optimal habitat selection. We also observed an interaction between habitat and dolphin behavior, suggesting the existence of functional habitats: foraging was more common in nearshore habitats with probable higher prey density while resting and socializing were more common further from shore. Similarly, females with calves were preferentially found in shallower waters compared to other social groups. We did not observe any effects of anthro-pogenic disturbance variables and therefore cannot conclude on the risk-disturbance hypothesis for this population.