Big herbivores, such as the wild boar (Sus scrofa) and the roe deer (Capreolus capreolus) are very common in Western Europe, so much that they cause numerous social, economic and environmental problems. For example, the Forestry Commission for Scotland estimates that damage to forests caused by deer costs them around £4.5 million (about €5.2 million) every year [1]. Similarly, millions of euros are paid out annually by EU governments to farmers in compensation due to damages caused by wildlife [2]. In France, compensation for crop damage caused by wild boars increased from €2.5 million in 1973 to € 32 million in 2008 [3].
Image 1. Wild boars remove soil in search of food. Source: University of Kentucky Department of Forestry and Natural Resources, Forestry Extension.
Big herbivores remove the soil in search of food such as worms, snails, plant roots, truffles and in some cases small vertebrates (e.g. lizards and frogs) (Image 1). When populations of big herbivores are under control, they contribute to the health of the ecosystem by dispersing seeds, controlling plant pests, and aerating and mixing the soil. However, due to the extremely low number of their predators, such as the grey wolf (Canis lupus) and the lynx (Lynx lynx), the populations of these big herbivores are out of control in many places across Europe. There are many methods that have been used to control the populations of these animals, such as recreational hunting, the use of snares, and poisoning, etc. However, these methods are either inhumane or useless on a large scale [4].
Electric fences and surveillance technology coupled with noise-producing devices have proven to work; however, they tend to have high initial setup and maintenance costs. They also interfere with the movement and natural behaviour of other animals. For example, noise can interfere with bat echolocation or with insect and frog callings.
More natural methods have been used by farmers, hunters and gardeners to keep herbivores away from their areas of interest. These methods include using wolf urine, using female pheromones to attract males to other areas, and using human hair (which smell apparently wild boars strongly dislike). There are also industrial repellents that use biodegradable granules that when scattered around the crops keep animals away. These granules have a strong smell and a bitter taste. But, as you would imagine, these products work better in small areas and have to be replaced regularly.
Image 2. Some methods used to control and/or repel big herbivores such as the wild boar and roe deer. From left to right: hunting, electric fences, wolf urine and biodegradable repellent. Sources: Hunting Fishing TV, Gallagher EU, 333shop.com, MondoVerde.
There are numerous reports that these natural methods work (Image 2). However, we cannot forget that if these animals are hungry or thirsty enough, they will likely not respect any barriers. This is why ensuring some areas where these animals can roam and forage freely is also very important.
At GreenPRAXIS, we will like to test some of these methods, so stay tuned to read more about our findings!
References
The management of wild deer in Scotland: Deer Working Group report. 2020. https://www.gov.scot/publications/management-wild-deer-scotland/pages/19/
Schlageter A. and Haag-Wackernagel D. 2012. Evaluation of an odor repellent for protection crops from wild boar damage. Journal of Pest Science 85: 209-215.
Maillard D. et al. 2010. Ungulates and their management in France, in European ungulates and their Management in the 21st Century, ed. by Apollonio M, Andersen R and Putman R. Cambridge University Press, Cambridge, UK, pp. 441–474.
Massei G. et al. 2011. Too many hogs? A review of methods to mitigate impact by wild boar and feral hogs. Human-Wildlife Interactions 5(1):79–99.