Sudden noise changes through boats abruptly altering course or speed are known to startle sperm whales at Kaikoura. Even placing motors in and out of gear can elicit a negative reaction. Accordingly, the regulations prohibit vessels from making sudden or repeated changes in speed or direction. Besides the literature review and assessment of sound transmission through sea water, two specific field projects have been commissioned by the Department of Conservation to assess the impact of marine mammal watching on sperm whales at Kaikoura. The latter study investigated underwater acoustic behaviour as well as surface behaviour.
Responses are highly variable between individual whales.
On average, however, whales appear to spend shorter periods on the surface and have shorter ventilation intervals when boats are around. Ventilation rates also seem to be more variable when boats are present. Such shallow dives are thought to be evasive manoeuvres and generally occurred when boats failed to follow the regulations. Since 1993, Drs Steve Dawson and Elisabeth Slooten of Otago University, in association with a number of their students, have been conducting a long-term study of the Kaikoura sperm whale population. The study is focused on individual identification, growth rates and the development of acoustic survey techniques, but it has also provided information on the seasonal distribution and behaviour of sperm whales that is of relevance to management of whalewatching operations.