| A complex and unresolved problem in wildlife management is detecting whether human activities, which superficially appear to be benign, have cumulative effects that are harmful to wildlife populations. For instance, current understanding of impacts of nature-based tourism on free-ranging cetaceans is far from satisfactory. To ensure the sustainability of the economically-important and rapidly-growing global cetacean-watching industry, there is a pressing need for sound scientific evidence on which to base management.; In a review of the literature pertaining to the evaluation of impacts of nature-based tourism on cetaceans, I identified factors that have limited the utility of this research, and pinpointed factors that allow for effective impact assessment. With this in mind, the Indo-pacific bottlenose dolphin (Tursiops sp.) population in Shark Bay, Australia, was identified as a system where all key factors could be incorporated into one impact assessment study.; I designed a multi-faceted study that incorporated experimental vessel approaches to dolphins that had differing histories of exposure to tourism. The long-term nature of the Shark Bay research project (>20 years) allowed for interpretation of short-term responses within a longitudinal perspective by providing information on two fundamental measures of population health, dolphin habitat use and female reproductive success, in response to increased vessel activity over a 14-year period.; Canonical-variate analyses showed that experimental vessel approaches elicited significant changes in patterns of sociality and movement of targeted dolphins at both control and tourism sites. Responses at the control site were stronger, more prevalent, and longer lasting than those at the tourism site. The moderation in the short-term responses at the tourism site was likely not the result of habituation to vessel activity, but could be better explained by a displacement of sensitive individuals during the development of the tourism operations.; Habitat use by individual dolphins was compared between three successive 4.5-year periods in which dolphins were followed by research vessels and no dolphin-watch tour vessels (T0), one tour vessel (T1), and two tour vessels (T2), respectively. In the tourism site from T1 to T2, there was a 1.78 fold increase in the time vessels spent with dolphins, of which 74.9% could be attributed to tour vessels. As the number of tour vessels increased from one to two, there was a statistically significant average decline of 14.9% in numbers of individuals per square kilometer in the tourism site and a non-significant average increase of 8.5% in the control site. (Abstract shortened by UMI.)... |
