Dolphins are increasingly coming into contact with humans, particularly where tourism is involved. It has been assumed that such contact causes chronic stress on dolphin populations. This study examined relatively naive populations of Hector's dolphins and their interaction with various watercrafts. Dolphins in New Zealand have been observed using theodolites and boat-based observations over the last two decades, particularly on the east side of the South Island at Akaroa, which is situated on the coast line of Banks Peninsula. This research was undertaken using shore-based theodolite tracking to observe boat activity around the coast of Lyttelton and Timaru and their associated Harbours. Observations were made mostly over two periods each of six months duration and included the months October through to March during the years 2000-2001 and 2001-2002. Observations made during a third period in 2005 were also incorporated for some of the analyses. Field investigations using a theodolite included more than 376 hours/site/season and recorded dolphin behaviour both with and without the presence of tour boats. Of primary interest were the tours, which ran regular trips to observe Cephalorhynchus hectori in their natural habitat. Hector's dolphins at both Lyttelton and Timaru were consistently observed with particular boat types and not with other types of water craft. Dolphins at Timaru exhibited a greater range of behaviours than those at Lyttelton. Stress-related behaviours such as an increase in swimming speed to open ocean and grouping behaviour were only observed in the presence of boats. Other potential stress behaviours, such as head slaps and repeated tail slaps, were only performed in the absence of boats. Observations implied that some generic dolphin behaviours, which often indicate stressed individuals may not apply to Hector's dolphins, and therefore question the assumption that all dolphin species behave in similar ways. We suggest that low-level tourist boat activity is not placing undue stress on the population. In addition to theodolite observations, tour boat based observations of Hector's dolphin were undertaken and behaviour at each site recorded for a focal animal. Tour boat-based observations concentrated on determining any preference to bow, stern, portside and starboard sides of the vessel. Dolphins consistently showed a preference in direction of approach and departure from tour vessels with a strong tendancy to the bow of the boat, and least with the stern. These results were similar irrespective of site or vessel. Behaviour data were also collected from tour boat vessels over 48 trips/season/site and the data divided into transitional behaviour groups, which included stress behaviours, association / interaction behaviour and neutral behaviour. Behavioural count and time data were collected to reflect the number of times and duration of behaviour occurrence, particularly in relation to transitional behaviours. Determining the presence of stress in Hector's dolphins varied between the data sets and indicated that time is a necessary factor when attempting to determine whether an individual or a general population is genuinely stressed. Quadrant preference and swimming direction in relation to the Black Cat were observed over six years, and both count and time data were collected with regard to behaviour. The results were consistent with preference in quadrant being expressed towards the bow of the boat and least with the stern. The count data suggested no significant impact on Hector's dolphin behaviour in the presence of the Black Cat over time, where time data indicated there was a transition over the years from neutral behaviour in the second year of tour boat activity, to positive behaviour in the third year of boat-activity and finally avoidance behaviour in the seventh year of tour boat activity at Lyttelton Harbour in response to the presence of the Black Cat.
Mason N McLary
|Location of Publication||Lincoln, New Zealand|
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