Movement patterns, behaviors, and whistle sounds of dolphin groups off Kaikoura, New Zealand
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The dusky dolphin (Lagenorhynchus obscures) is a small delphinid that occurs in temperate waters near Southern Hemisphere land masses. Off Kaikoura, New Zealand, duskies are targeted for interactions by tourist vessels, swimmers and recreational vessels. To determine if human activity influenced dolphin behavior, I conducted shore- and vessel-based studies to examine movement patterns and acoustic behavior of huskies during three field seasonal Small groups of 25 or fewer dolphins were tracked from shore with a theodolite. Three variables; mean leg speed, linearity, and reorientation rate, were examined to determine possible influence of year, season, presence of a calf, time of day, group size, or presence of vessels within 100m, 101-300m and 301-1,000m. Mean leg speeds did not differ significantly by year, season, presence of a calf, or time of day. For group size comparisons, a post-hoc linear regression found a significant relationship between mean leg speeds and group size (p=0.0472). Mean speeds for groups containing 6-10, 11-15, and 16-20 animals increased as group sizes increased. Mean leg speeds did not differ by presence of a vessel within 100m, 101-300m, or 300-1,000m. For shore-based studies, mean leg speed may not be the most appropriate parameter to determine effects of human activity. Linearity, a measure of how straight a course was traveled, increased when boats were within 100-300m. Higher values were recorded during boat and post boat conditions than during no boat conditions, indicating that dolphin groups traveled in a more direct fashion during these times. A post-hoc analysis revealed a significant difference between no boat and a combined boat/post boat condition (p=0.0419). Reorientation rates were higher when boats were within 101-300m, indicating that dolphins changed course more often when boats were present. Whistles were recorded when duskies were associated with common dolphins (Delphius delphis), with swimmers, or when duskies were alone. Over 97% of analyzed whistles were recorded when duskies were found in inter-species groups. Whistles may be an indication of excitement levels within the group. More work is necessary to determine if whistles can be used as a reliable indicator of disturbance.
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Includes bibliographical references (leaves 80-91).
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Yin, Suzanne E (1999). Movement patterns, behaviors, and whistle sounds of dolphin groups off Kaikoura, New Zealand. Master's thesis, Texas A&M University. Available electronically from