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The effects of tour boats on the behavior of bottlenose dolphins: Using Markov chains to model anthropogenic impacts

Authors

Lusseau,D.L.

Year

2003

Journal

Conservation Biology

Volume

17

Issue

6

Pages

1785-1793

Keywords

behaviour, bottlenose dolphin, cetacean, cetaceans, disturbance, dolphin watching, ecology, impact, management, new Zealand, occurrence, population, tourism, whale, whale watching

Abstract

Nature-based tourism activities have been developing over the last decade, yet we still have difficulties managing these activities sustainably. This sector is increasingly focusing on whales and dolphins incoastal communities. The exact effects of these activities are still unclear. Markov chain modeling may help researchers to assess the effects of tourism activities on the behavioral budget of small cetaceans. Matrixmodels have been widely used in population ecology to provide successful management guidelines. From June 2000 to August 2001 I collected information on the behavioral state of bottlenose dolphin schools from a population residing in Doubtful Sound, Fiordland, New Zealand. In addition, I recorded the occurrence of boat-dolphin interactions. I then calculated transition probabilities of passing from one behavior to another by using a first-order time-discrete Markov chain model. Behavioral transitions during which a boat-dolphin interaction occurred were compiled in an "impact" chain. All other transitions were tallied in a control chain. The effect of boat-dolphin interactions during behavioral transitions was then quantified by comparing the behavioral transition probabilities of both chains. Socializing and resting behaviors were disrupted by interactions with boats to a level that raises concern. Both the duration of bouts and the total amount of time spent in both these behavioral states were substantially decreased. Dolphins were significantly more likely to be travelling after an interaction with a boat. However the overall behavioral budget of the population was not significantly affected. Therefore the bottlenose dolphin population seems to be able to sustain the present level of interactions because of the low intensity of boat interactions. More effort is needed todevelop prognosis analyses in order to understand how the effect of boat interactions changes with variations in intensity.
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