New research shows that the mere smell of predators is enough to change deer behavior and limit browsing damage to tree saplings. The findings offer a potential tool for forest recovery and highlight the important role large predators play. The research is published in the British Ecological Society's Journal of Applied Ecology.
Research conducted in the forests of south-eastern Germany, shows that the smell of large predators, like lynx and wolves, is enough to make deer more cautious and spend less time eating tree saplings.
In an experiment that involved adding lynx and wolf urine and scat to plots of saplings, researchers from the University of Freiburg found that plots with the scent of predators, particularly lynx, had less browsing damage to young trees than control plots. Deer visited predator-scented plots less and spent less time foraging when they were there.
Over browsing from deer is a major threat to forest regeneration, damaging biodiversity and causing economic losses for the forestry sector. Mitigating browsing damage usually involves substantial human effort and financial resources.
Walter Di Nicola, one of the lead researchers, said: "At a time when debates around large carnivore conservation often focus on conflicts, our study highlights the benefits these species bring to landscapes. The presence of carnivores, even just their scent, could help reduce the ecological and economic problems associated with browsing from overabundant deer populations."
The research was conducted in forests where both lynx and wolves have been reintroduced. But the researchers say they would expect similar effects in countries like the UK where these predators have long been absent.
Walter said: "In the UK we would expect similar but probably weaker effects. Deer still have some innate fear of predators, even if those predators have been absent for generations. Where predators return, we expect these responses – and their ecological benefits – to become stronger over time."
The researchers call for conservation strategies that promote large carnivores in forests as a natural, low-intervention solution to over browsing.
To test the effects of large carnivore smells on deer behavior, the researchers set up experimental plots at 11 locations around the forests. Each location comprised of four plots marked with the scent of wolf, lynx, cow and water (as a control). In each plot 30 saplings were planted.
The researchers regularly monitored the saplings to assess browsing damage and used camera traps to record red and roe deer behavior, such as how long and how frequently they visited each plot.
The researchers found that there was a stronger response to the smell of lynx compared to wolf. They believe this could be due to the ambush hunting strategies of lynx, which tend to stalk their prey from close distances, meaning deer might perceive lynx scent cues as more of a threat.
They also point out that wolves were establishing themselves in the area at the time of the experiment, and the deer had much more experience of the threat of lynx.
The researchers caution that their experiment cannot fully replicate the complexity of natural-predator prey interactions. In their set up they used concentrated predator scents, which were easier for deer to detect than in natural conditions. In the wild, real predator cues are more scattered and unpredictable.
