Changes in behaviour can adversely affect wildlife and reduce the effectiveness of management operations. Bleich et al. (1994) suggested that frequent disturbance by aircraft could cause animals to vacate their home territory. The distance from the source of disturbance is an important indicator of alert behaviour. Goats displayed alert behaviour when the helicopter was directly overhead and alert response decreased exponentially with horizontal distance from the helicopter. The distance moved decreased sharply when the helicopter was further than 150 m away. Goats were often disoriented and ran away to a distance up to 1.5 km in response to helicopter over-flights. However, Tracey and Flem (2007) found that helicopter flights did not cause mothers to abandon their young, nor adversely affect their immediate or long-term welfare. Feral goats displayed aversion and learnt to respond to helicopter disturbance (Tracey and Flem, 2007).