Oxford team develops hedgehog test for robot lawnmowers

Hedgehog populations are in decline all across Europe, driven by habitat loss, intensive agriculture, and injuries from road traffic, dog bites and garden strimmers. Increasingly, hedgehog injuries are also being attributed to robot lawnmowers, as the devices become more popular.

Having previously conducted a study on the impact of different robot lawnmowers on the carcasses of dead hedgehogs, Dr Sophie Lund Rasmussen – known on YouTube under the moniker Dr Hedgehog – has now devised a test using hedgehog ‘crash test dummies’ made from a pliable plastic. It is hoped that manufacturers of robot lawnmowers will be able to 3D print these hedgehog analogues in order to improve the safety features of their devices.

“There is an urgent need to identify and phase out models of robotic lawnmowers that pose a threat to hedgehogs,” said Dr Rasmussen.  

“Our new standardised safety test will greatly aid hedgehog conservation, by enabling manufacturers of robotic lawnmowers to ensure their models are ‘hedgehog friendly’ before they are put on the market.”

To make the test as realistic as possible, the team worked with a hedgehog rehabilitation centre in Denmark to establish how live hedgehogs react around robotic lawnmowers. They tested the responses of fifty hedgehogs in an enclosed environment to a bladeless robotic lawnmower that was stopped 50cm away from the hedgehog.

The hedgehogs demonstrated three main responses: running away from the mower; standing rigidly in front of it partially curled up; and sniffing the lawnmower inquisitively. Generally, younger hedgehogs tended to be more inquisitive than adult hedgehogs.

“Each hedgehog was tested twice and, interestingly, they tended to act more shyly on their second encounter,” said Dr Rasmussen.

“This is hugely important, since it suggests that hedgehogs may learn from their first encounter with a robotic lawnmower. Potentially, if a hedgehog survives its first encounter with a robotic lawnmower, it is less likely to be injured in the future because this may cause it to avoid them.”

According to Dr Rasmussen, the ultimate goal is a certification scheme that will enable consumers to choose ‘hedgehog friendly’ devices that present a significantly reduced threat to the mammals.

“A key first step is to improve the sensors, so that they detect the hedgehogs and avoid them,” she said.

“Developing additional technologies such as camera recognition could eventually allow the robotic lawnmowers to detect hedgehogs at a distance and change direction before they get close. It is also important that the blades of the mowers are pivoting, so that they fold away under a protective surface when hitting something harder than grass.”