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.