A study of the relationships between the behaviour of cetaceans and vessel traffic using two case studies : Killer whale (Orcinus orca) and Humpback whale (Megaptera novaeangliae : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology, Massey University, Auckland, New Zealand
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Date
2009
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Massey University
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Abstract
Two studies were carried out to describe the relationship between vessel presence on the behaviour of both whales and dolphins. Each study conducted focal follows on members of two endangered sub-populations using a land-based theodolite station in order to track and mark positions of opportunistic vessel traffic in relation to animal surfacings. Southern resident killer whales (Orcinus orca) were theodolite tracked during the months of May-August for three field seasons (1999-2001), off San Juan Island, Washington State, U.S.A, in an independent study. Migrating humpback whales (Megaptera novaeangliae) were theodolite tracked off Moreton Island, Queensland, Australia during 2005 from May-September in partial fulfilment for a Master of Science degree. For each study, four dependent whale variables were analysed in relation to two boat variables. Whale variables included mean time per dive (dive time), swimming speed, directness of path traveled (directness index) and the number of surface behaviours per hour such as breaches or tail-slaps (surface active behaviour). The two boat variables included a count of the number of boats within the study area during each tracking session (boat count) and the point of closest approach (PCA) by a vessel to the focal animal during the tracking session. Southern resident killer whales were found to decrease path directness with the point of closest approach of vessels. As whales adopted a more circuitious path, distance travelled increased by 9.5% when boats were within 100 m. Humpback whales significantly decreased their rate of surface active behaviour by 50% when boats were present. This thesis presents data that show a snapshot of the levels to which both species are exposed to vessel traffic, as well as subtle short-term behavioural responses in relation to vessel presence. I compare the impacts of vessel traffic identified for the two species, and suggest possible long-term population consequences due to potential interruptions of foraging and/or social behaviours. I discuss limitations of small data sets such as these and discuss ways in which further research can be better designed. Deliberate planning of vessel effect studies and their subsequent analyses can provide conservation managers useful information for determining recovery strategies of endangered whales and dolphins.
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San Juan Island Washington (State), Human-animal relationships, Whale watching industry, Kiler whale behavior, Effect of human beings on Killer whale, Humpback whale behavior, Effect of human beings on Humpback whale, Queensland -- Moreton Bay Marine Park