Impacts of Ecotourism on Short-Beaked Common Dolphins (<I>Delphinus delphis</I>) in Mercury Bay, New Zealand

Abstract

Short-beaked common dolphins (Delphinus delphis) often are found in large aggregations offshore from the eastern coast of New Zealand. They are the primary target of at least six marine mammal tourism operations from Whakatane to the Hauraki Gulf. This report details the first longterm investigation of interactions between tourists and common dolphins. During a 3-y study offshore from Whitianga on the Coromandel Peninsula, 105 focal group follows, totaling 118 h of observations were conducted from a 5.5-m, rigid-hull inflatable boat. Seventy-two of these observations were conducted in the absence of the tour boat (baseline), and 33 with the tour boat. Baseline data were compared with “tour boat” data to assess changes in dolphin behaviour resulting from the tour boat approaching and swimmers entering the water to snorkel with the dolphins. Common dolphins responded with a relatively predictable pattern to approaching boats. Initial attraction (mean duration 8 min) typically was followed by neutral behaviour (mean duration 57 min) and eventually replaced by boat avoidance. Smaller dolphin groups showed boat avoidance sooner and more frequently than larger groups. When swimmers entered the water, dolphins only spent an average of 2 min in their vicinity. Throughout encounters, they maintained a distance of at least 3 m from the nearest swimmer. During half of the attempted swims, dolphins did not change their course or their activity in response to swimmers. Swimmers had a better chance of a sustained interaction when the group of dolphins was large (> 50 individuals) and/or the number of swimmers in the water was small (< 5). The results of this study suggested that common dolphins can be affected by tourism; however, adherence to New Zealand’s Marine Mammals Protection Regulations and the current low level of tourism appear to minimise the impact on this species.