Behavioural Responses of Ungulates to Sound Systems : can simulated risk influence behaviour?

Abstract: Increasing ungulate densities all over Europe are intensifying the ongoing human-wildlife conflict, embodied by mainly economical losses through damages in forestry and agriculture. Given the current circumstances, farmers and forest owners prefer a decrease in ungulate numbers through direct population control, whereas other stakeholders, such as hunters, wildlife watchers or photographers, prefer higher wildlife numbers. This challenging contradiction requires novel management approaches. The landscape of fear theory implies behavioural changes in prey by not the direct killing, but the fear of predators, which can cause trophic cascades down to vegetation level. Here, I used Automated Behavioural Response systems (ABR) to experimentally induce this landscape of fear for ungulates in two study areas in southern and northern Sweden and to evaluate three behavioural responses: leaving rate, foraging behaviour, and vigilance behaviour. I used different risk sounds (human, dog and wolf sounds) and a non-risky control sound (different native bird species). The ABRs were placed along the edges of crop fields and close to other lure types, such as salt licks, to test for fear responses in situations where resources were plentiful. The results show that ungulates were significantly more likely to abandon the site when they were exposed to risk sounds than to control sounds, where the effect of the human sound exceeded the other risk sounds by far, and therefore supports the ‘human super-predator’ theory. Furthermore, they decreased foraging time and increased vigilance levels for risky sounds. Distance of the animal to the sound source played an important role for behavioural responses, as well as group size (only applied for fallow deer), which reflects a known anti-predatory strategy. With increasing distance, ungulates left the area fewer times, increased their foraging time, and decreased their time being vigilant. The same behavioural response patterns were shown for larger fallow deer groups compared to single individuals. Overall, human sounds showed to be most effective, followed by wolf sounds. Dog sounds played only a minor role in altering ungulates‘ behaviour. The results of this study show that it is possible to affect and alter ungulates behaviour through a locally human-made landscape of fear. Thus, the knowledge about the behavioural effects could contribute to a potential conflict minimisation of the ongoing human-ungulate issue.