While Americans still wrangle their overgrown lawns by pushing or riding a lawnmower, many Europeans have handed off that responsibility to robots. These beefy, Roomba-like mowers loop their way around a yard, keeping grass trim and neat.

To many of their users, the bots are endearing. Their owners give them names or cover them in decals of ladybugs or bumblebees. But the sentimentality only goes so far, because these blades-on-wheels have also been slicing up something other than grass: hedgehogs.

Erika Heller, a long-time hedgehog advocate with a Swiss nonprofit called Igelstation Winterthur, estimates that nearly half the hedgehogs brought to the group during the last couple years were injured by robot lawnmowers, though experts caution that no precise numbers exist. These injuries include limb amputation, cut bellies, or even scalping. And that's not including the ones that have been killed outright. “The ones that have died we don’t see, because they don’t get brought here.”

In the United States, despite a wealth of children's toys and clothing featuring hedgehogs, the only live animals you’re likely to see are in the zoo or, more controversially, kept as pets. But in Europe, wild hedgehogs are beloved. They’re popular in European folklore; there's even a famous British poem about a hedgehog killed by a lawn mower.

And they have their champions: Across Europe, numerous advocacy groups exist specifically for hedgehogs. These groups are the ones now sounding the alarms about these landscaping robots. Robo-mowers rank low in the robot hierarchy; they come equipped with basic sensors that prevent them from running over or colliding with larger objects, such as large rocks or trees, but they often miss smaller things, like young hedgehogs. Other animals, like birds or rodents, would flee an advancing bot. Not hedgehogs. Instead of running away from danger, they curl up in a ball. This response causes them to sometimes lose a limb or get scalped. Sometimes they die on the spot.

Though uncommon in the US, robot lawnmowers are big business in Europe. Global sales of the bots are expected to surpass $3 billion by 2023. The service robots are programmed to keep lawns well-maintained, usually running every other day or so, gliding quietly, snipping away at grass, returning after their rounds to a charging station.

Husqvarna, the biggest manufacturer of robot lawnmowers, says it is working on ways to keep hedgehogs safe. Margaretha Finnstedt, the company’s director of public relations, says that the number of hedgehogs injured by robot lawnmowers is low, adding however that “any number is too big.”

One way Husqvarna tries to mitigate danger is by only building robot mowers with pivoting blades instead of fixed blades. Fixed blades cut faster and with more force, making them more dangerous to animals as compared to pivoting blades, which rotate on a disc and, like a grazing animal, snip off the tops of grass blades with less oomph.

The company is also considering more creative solutions. “We’re looking at one high-tech and one low-tech way to go,” says Olle Markusson, Husqvarna’s director of product management for robotic mowers. The high-tech option is to have a camera that can look out for animals around the product. Low-tech? The “mustache,” a small broom attached to the mower’s undercarriage to sweep objects like young hedgehogs out of the way.

Hedgehog advocacy groups also run safety tests on the mowers, using apples to represent young hedgehogs and cabbages for adults. The produce is placed around lawns and different robot mowers are let loose. The tests found that mowers with a clearance of more than 2 inches were the most dangerous, because they were high enough to glide over a young hedgehog, creating room for its blades to cut the animal.