Publication Date:
2024-07-05
Description:
The results of this study show that close boats (〈100 m) affect the behaviour of bottlenose dolphins more strongly than boats further away (〉100 m). Close boats induced a decrease of feeding, resting and social behaviour. The proportions of high-speed swimming and slow swimming increased. In the presence of close boats, dolphins were observed 6 times more frequently to leap and 3.6 times more frequently to tail-slap than under control conditions – an indication of disturbance. Dolphins responded to close boats with evasive manoeuvres similar to techniques used for avoiding predators. With more than two close boats, animals swam approx. 37% faster than without close boats. An energy consumption of 2.93 W kg-1 was calculated. This corresponds to a daily energy demand of 50.6 MJ per dolphin with 200 kg body weight. With boats at close range, the mean power requirement of dolphins was around 15.4% higher than during controls. With close boats, dolphins used a third of their energy budget to avoid boats by swimming at high speed. In the light of these findings, recommendations for dolphin-watching guidelines are given.
Type:
Thesis
,
NonPeerReviewed
Format:
text
