By Nina Hermansen and Jeannette Bylov, AAU Communication and Public Affairs

Robotic lawnmowers are becoming increasingly popular, but unfortunately, some models pose a risk to the already endangered hedgehogs. In recent years, many so-called hedgehog care stations, which assist sick hedgehogs, have reported an increase in the number of animals with injuries likely caused by the new robots.

Now, a team of researchers led by zoologist and behavioural biologist at Oxford University and guest researcher at Aalborg University, Sophie Lund Rasmussen, can present a new safety test that enables manufacturers of robotic lawnmowers to ensure that their models are "hedgehog-friendly" before they are released to the market.

Young hedgehogs are like teenagers

The researchers tested fifty hedgehogs ready to be reintroduced into nature after being cared for at the Animal Protection's wildlife care station. The hedgehogs underwent a series of harmless tests, where the researchers first examined the animals' personalities and then their reactions to encountering a (bladeless) robotic lawnmower that never got too close to the hedgehogs.

Sophie Lund Rasmussen, also known as Doctor Hedgehog, is very surprised by the results:

- The hedgehogs actually reacted quite differently than I had expected. Overall, they had three different reactions: they either ran away from the machine, stood stiffly in front of the robotic lawnmower in a partially curled-up position, or curiously sniffed at the lawnmower. In general, younger hedgehogs were braver than adult hedgehogs. Yes, one could actually say that young hedgehogs are like teenagers – much less cautious than adults.

Each hedgehog was tested twice, and interestingly, the study showed that hedgehogs tended to be much more cautious the next time they encountered the robot – regardless of age.

 - This is extremely important because it suggests that hedgehogs can learn from their first encounter with a robotic lawnmower. If a hedgehog survives its first encounter with a robotic lawnmower, it is less likely to be harmed in the future, says Sophie Lund Rasmussen.

 

Hedgehog model available in 3D-print

Based on the results, the researchers have developed a model of a hedgehog that can be 3D-printed. They have also identified the key positions in which the model should be placed to simulate realistic reactions from a live hedgehog in connection with a safety test. The dummy is made of soft plastic and mimics the body composition of a real hedgehog.

- Our goal is to make the model's design publicly available for 3D printing so that companies can use the dummy when developing hedgehog-friendly robotic lawnmowers. Now the work begins to integrate the safety test into the official test protocols approving lawnmowers for sale in the European market. It will also enable the implementation of a certification scheme, guiding consumers to choose models of robotic lawnmowers that are safe for hedgehogs.

In the upcoming months, Sophie Lund Rasmussen and colleagues will continue working on their model, and soon they will embark on a new project to investigate hedgehog hearing.

- If we can find out that hedgehogs can pick up specific sound frequencies, we may be able to develop lawnmowers that emit warning signals, potentially causing hedgehogs to avoid them. This aspect of our research is particularly compelling as it involves identifying problems and working collaboratively with the industry to find solutions, ultimately benefiting hedgehogs by addressing practical concerns