NORTHERN RESIDENT KILLER WHALE RESPONSES TO VESSELS VARIED WITH NUMBER OF BOATS

• Main Authors: Rob Williams, Erin Ashe
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2006
• Subjects: British Columbia; Canada; Killer Whale; Killer whale
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.580.734; http://www.orcarelief.org/docs/williams_ashe.pdf

Vessel traffic has been implicated as a potential contributing factor to the at-risk status of two killer whale populations in western Canada and the US. Whalewatching guidelines can help mitigate this potential threat, especially when these are developed using experimental impact assessments that allow animal response to inform vessel management. Two published experimental studies on one of these populations documented stereotyped avoidance responses. Opportunistic observations in these studies in the mid-1990s suggested an inflection point in avoidance behavior when approximately 3 boats approached whales to within 1000m. Our experiment was designed to test whether whales responded differently to approach by few (1-3) versus many (>3) vessels. Data were collected in summer 2004, in Johnstone Strait, British Columbia (BC), Canada, using a theodolite to track positions of boats and individually identifiable whales. Experimental trials included 20-minute “no boat ” and 20-minute “boat ” phases (with local whalewatching vessels volunteering to act as experimental treatments), during which data were collected continuously on the focal whale. Responses of the 16 adult male killer whales tracked differed significantly between treatment levels (Wilcoxon’s test P=0.0148). Swimming path