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Experimental evidence for large carnivore risk cues reducing deer browsing intensity in a temperate forest

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Nov 24, 2025 version files 627.54 KB

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Abstract

Intensive ungulate browsing represents a major challenge for managing temperate forests, and only a clear understanding of the underlying ecological processes can help to mitigate its impact. Predator-prey interactions play a crucial role in shaping browsing patterns; however, the lack of a comprehensive understanding of these dynamics hinders the development of functional policies. Using an experimental approach, we simulated large-carnivore presence using olfactory cues to examine the effects of predation risk on deer behaviour and its consequences for browsing intensity on tree saplings. We conducted this experiment in eleven locations in the Bavarian Forest National Park (Germany), each comprising four plots with olfactory cues of wolf, lynx, cow, and water (control). In each plot, we planted 30 saplings representing the five most common tree species in the area, which we regularly monitored to assess browsing intensity and selectivity.  In addition, we set a camera trap at each plot to record deer species (red and roe deer), age, sex, and behavioural metrics like time spent vigilant, visitation duration, and visitation frequency. This experimental design allowed comparisons of the effects of different large carnivore on prey species while measuring browsing intensity. Our results demonstrated that deer modified their behaviour in response to large carnivore scent cues compared to non-risky cues, with more pronounced effects in lynx treatments compared to controls. Red and roe deer spent significantly less time in lynx treatments compared to controls, especially at dawn and dusk. In spring at dusk, we observed similar decreases in visitation duration in wolf treatments. Notably, our findings also show increased vigilance time of adult deer accompanied by juveniles at sites with lynx cues during winter nights. As a consequence of these behavioural changes, we recorded a significant reduction in browsing intensity in lynx treatments compared to controls. However, no signs of tree species selectivity were found in plots with large carnivores scent cues nor differences in visitation frequency. Synthesis and applications: By analysing multiple behavioural responses and considering relationships between different trophic guilds, we provide unique insights into the mechanisms of predator-prey interactions and their indirect impact on forest ecosystems. In particular, our findings highlight the role of large carnivores in mitigating ungulate browsing damages, which is important for managing temperate forests (both natural and commercial) where herbivore browsing is a significant pressure.