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Visual-acoustic wildlife deterrents as a supporting measure to prevent mowing-related mortality in roe deer fawns

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Jul 30, 2025 version files 36.66 KB

Abstract

Mowing-related mortality is one of the main causes of death among roe deer fawns in agricultural regions, prompting farmers in Germany to implement preventative measures. Understanding the effectiveness of different deterrent methods is crucial to reducing such mortality.

This study examined the effectiveness of visual-acoustic wildlife deterrent devices in preventing roe deer fawns from entering agriculturally used areas before mowing, encouraging those already present to leave, or facilitating their removal by their mothers. A total of 76 fawns were fitted with GPS-collars between 2022 and 2023, and their movements were analysed using a multi-state Markov model. 

Our results demonstrate that visual-acoustic wildlife deterrents significantly influenced fawn behaviour, with 36% of the fawns leaving the trial area and not returning at all during the trial period. However, this indicates a substantial risk of injury or death for the fawns remaining in the fields during mowing. Among the tested devices, electronic acoustic deterrents, particularly smoke detectors, were the most effective deterrents, scaring away over 50% of the fawns without any significant habituation effect. 

The probability of fawns leaving the meadows was further influenced by several factors such as age, proximity to forest edges, vegetation height, and field size. Younger fawns, following a "hider" strategy, were less likely to leave the agriculturally used areas, whereas older fawns exhibited higher mobility. Fawns more frequently remained in areas with tall vegetation and large field sizes, while deterrents proved more effective in smaller fields and near forest edges. 

Despite some success, the limited efficacy of the tested deterrent devices highlights the necessity for additional measures, such as using drones equipped with thermal imaging cameras, to further reduce fawn mortality during mowing. Our findings provide critical insights for improving wildlife management practices in agricultural landscapes and reducing roe deer fawn losses during the mowing season.