Dusky dolphin and tourist interaction: effect on diurnal feeding behavior

DANS, SILVANA LAURA; CRESPO, ENRIQUE ALBERTO; PEDRAZA, SUSANA NOEMI; DEGRATI, MARIANA; GARAFFO, GRISELDA VALERIA

MARINE ECOLOGY PROGRESS SERIES

INTER-RESEARCH

Año: 2008 vol. 369 p. 287 - 296

0171-8630

Dolphin-watching is a relatively newly developed tourism activity. Although it is assumed it contributes to the conservation of marine ecosystems, its long-term adverse effects are still unknown. The goal of the present work was to assess the impact of tour vessels on the behavioral pattern of dusky dolphins displaying diurnal and cooperative feeding. We evaluated potential bias of commercial vessels on specific behaviors, short-term responses of dolphins to the approach and longer-term effects of these changes, particularly on the activity budget and the time dolphins need to resume an activity. Several field experiments were carried out approaching dolphins by a research as well as by commercial vessels. Group follows were also made from a research vessel. Behavioral sequences were modeled by stochastic matrix models. Activity budget and time to return to an activity were obtained from matrix properties. Commercial trips found mostly feeding groups. Feeding showed the highest rate of change at the moment the vessel approached dolphins, and the commercial vessel had an effect on the direction of change. In a longer-term, feeding and socializing time budget decreased when commercial vessels were present. The time to return feeding as well as the time it takes a group of dolphins to feed increased in presence of commercial vessels. Dusky dolphins in south atlantic waters feed during daylight on patchily distributed preys. Our study demonstrates behavioral responses of dusky dolphins to boats presence, which would negatively affect in a longer-term feeding efficiency.