A woman handles a hedgehog in England. (Photo by OLI SCARFF/AFP via Getty Images)
Hedgehogs are an unofficial and adorable mascot of the United Kingdom. The small spiny mammals can often be found in gardens, but the U.K.’s European hedgehog population is under threat from loss of habitat and the dangers of living in urban settings. One of those dangers is robotic lawnmowers.
A human with a lawnmower can keep an eye out for hedgehogs, but robots don’t have that same level of hedgehog awareness. A team of researchers has hatched a plan to make robot lawnmowers safer for the spiny critters. It involves “hedgehog crash test dummies” that could be used to certify hedgehog-safe mowers.
“There is an urgent need to identify and phase out models of robotic lawnmowers that pose a threat to hedgehogs,” said University of Oxford wildlife ecologist Sophie Lund Rasmussen. “Our new standardized 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."
Rasmussen led two studies published in the journal Animals in late 2023. The first paper explores how hedgehogs react to robotic lawnmowers while the second one details the development of the mower safety test.
The researchers used dead hedgehogs donated by rehabilitation centers to test 19 robotic lawnmowers and found the machines had to physically touch the animals before detecting them. In some cases, the mowers ran over the carcasses.
A 3D-printed hedgehog "crash test dummy" can be used for robotic lawnmower safety tests.
Another experiment examined how 50 live hedgehogs from a wildlife rehabilitation center reacted to robotic mowers. The blades were removed for safety and the mowers were stopped when they were within 20 inches of the animals. The mammals had different responses. Some ran away, some stayed in front of the mower and some sniffed it. “Each hedgehog was tested twice and, interestingly, they tended to act more shyly on their second encounter,” said Rasmussen. “This is hugely important, since it suggests that hedgehogs may learn from their first encounter with a robotic lawnmower.” To learn in the real world, however, hedgehogs must first survive the encounter. That’s where the crash test dummy comes in.
The dummy looks like an abstract version of a real hedgehog. It’s made from rubbery plastic and has an array of spines across the top. The researchers plan to make the model available so lawnmower manufacturers can 3D print the dummy and use it for testing. The team’s testing guidelines recommend running 60 trials with two different sizes of dummies in several positions to account for how the machines might encounter the animals in the real world.
Hedgehog researcher Sophie Lund Rasmussen poses with a hedgehog and a robotic lawnmower.
Rasmussen would like to see improvement in robotic lawnmower sensors alongside the addition of camera technologies that would help mowers identify and avoid the small animals.
The Red List for British Mammals, a catalog of threatened and endangered animals, classifies the European hedgehog as a vulnerable species at risk of possible extinction in the U.K. The Warwickshire Wildlife Trust cites habitat loss, predation by badgers, lack of food sources, vehicle strikes and garden injuries from tools, netting and dogs as factors impacting hedgehog numbers.
Britain’s hedgehog population has declined up to 75% in some rural areas since 2000, according to a 2022 report. However, some populations in urban areas were stable or recovering. That’s good news, but the report noted “that any recovery starts from a low baseline at the end of a long period of decline.”
Current owners of robotic lawnmowers can take steps to prevent hedgehog injuries by checking the lawn before operating the machine and by cutting grass during the day when hedgehogs are less likely to be active. Urban yards and green spaces are becoming important habitats for hedgehogs pushed out of rural areas, but human awareness and care are key to making gardens and lawns safe havens for the charismatic creatures.
