Scientific Literature: Searchable Database

Studies evaluating effects of human activity on wildlife typically emphasize short-term behavioralresponses from which it is difficult to infer biological significance or formulate plans to mitigate harmfulimpacts. Based on decades of detailed behavioral records, we evaluated long-term impacts of vessel activity onbottlenose dolphins (Tursiops sp.) in Shark Bay, Australia.We compared dolphin abundance within adjacent 36-km2 tourism and control sites, over three consecutive 4.5-year periods wherein research activity was relativelyconstant but tourism levels increased from zero, to one, to two dolphin-watching operators. A nonlinear logisticmodel demonstrated that there was no difference in dolphin abundance between periods with no tourism andperiods in which one operator offered tours. As the number of tour operators increased to two, there was asignificant average decline in dolphin abundance (14.9%; 95% CI=?20.8 to ?8.23), approximating a declineof one per seven individuals. Concurrently, within the control site, the average increase in dolphin abundancewas not significant (8.5%; 95% CI=?4.0 to +16.7). Given the substantially greater presence and proximity oftour vessels to dolphins relative to research vessels, tour-vessel activity contributed more to declining dolphinnumbers within the tourism site than research vessels. Although this trend may not jeopardize the large,genetically diverse dolphin population of Shark Bay, the decline is unlikely to be sustainable for local dolphintourism. A similar declinewould be devastating for small, closed, resident, or endangered cetacean populations.The substantial effect of tour vessels on dolphin abundance in a region of low-level tourism calls into questionthe presumption that dolphin-watching tourism is benign.