Facing Danger: Exploring Personality and Reactions of European Hedgehogs (Erinaceus europaeus) towards Robotic Lawn Mowers

Abstract

The populations of European hedgehog (Erinaceus europaeus) are in decline, and it is essential that research identifies and mitigates the factors causing this. Hedgehogs are increasingly sharing habitats with humans, being exposed to a range of dangers in our backyards. Previous research has documented that some models of robotic lawn mowers can cause harm to hedgehogs. This study explored the personality and behaviour of 50 live hedgehogs when facing an approaching, disarmed robotic lawn mower. By combining a novel arena and novel object test, we found that 27 hedgehogs could be categorised as “shy” and 23 as “bold”, independently of sex and age. The encounter tests with a robotic lawn mower showed that the hedgehogs positioned themselves in seven different ways. Personality did not affect their reactions. Adult hedgehogs tended to react in a shyer manner, and the hedgehogs, generally, acted less boldly during their second encounter with the robotic lawn mower. Additionally, our results show that bold individuals reacted in a more unpredictable way, being more behaviourally unstable compared to the shy individuals. This knowledge will be applied in the design of a standardised hedgehog safety test, eventually serving to produce and approve hedgehog-friendly robotic lawn mowers.

Testing the Impact of Robotic Lawn Mowers on European Hedgehogs (Erinaceus europaeus) and Designing a Safety Test

“…The findings of Rasmussen et al (2024) [ 36 ] showed that live hedgehogs tend to either run away or position themselves in positions 3, 5, and 6 ( Figure 1 ) when approached by a robotic lawn mower. As our tests showed that the position did not significantly influence the outcome of the collision tests, and as position 1 and 2 (curled up hedgehogs) would be challenging to mimic with a non-flexible hedgehog crash test dummy, we suggest excluding these two positions from the standardised safety test.…”

“…Based on the results reported by Rasmussen et al (2024) [ 36 ] testing the behaviour of live hedgehogs facing a disarmed, robotic lawn mower, each individual was tested in six different positions ( Figure 1 ) in an attempt to mimic the behaviour of a live individual. The most commonly recorded position during the tests on live hedgehogs was “upright position with snout pointing inwards” (43%) [ 36 ] which could not be properly mimicked with a dead hedgehog as the head would not bend inwards and stay in place, leaving us to combine this with the second most frequently recorded behaviour (20%), test position 3:…”

“…Unfortunately, sharing habitats with humans comes at a cost, as residential gardens provide many anthropogenic sources of danger to hedgehog survival. One of these potentially harmful features is certain models of robotic lawn mowers [ 26 , 35 , 36 ]. With robotic lawn mowers becoming increasingly popular throughout the distribution range of hedgehogs in Europe, there is a high likelihood for a hedgehog to encounter numerous robotic lawn mowers throughout its lifespan.…”

Applied Hedgehog Conservation Research

“…Studies by Rasmussen et al of robotic lawn mowers have shown important differences between models in the risk of injury to hedgehogs, creating the basis for specific design improvements to mitigate such risks [ 31 , 32 ]. Moreover, investigations of the personality and reactions of live hedgehogs towards a disarmed, approaching robotic lawn mower are also applied in the design of a standardised hedgehog safety test, eventually serving to produce and approve hedgehog-friendly robotic lawn mowers [ 33 ].…”