Robotic lawn mowers may not be operated during the period from half an hour before sunset to half an hour after sunrise. During the day, robotic lawn mowers may be used without restriction.

This measure is intended specifically to protect the Western European hedgehog. Hedgehogs are primarily active at dusk and at night. When in danger, hedgehogs curl up into a ball and cannot escape from the robotic lawn mower, which often results in serious injuries or fatalities. Gardens and green spaces in the city of Mainz serve as important habitats for hedgehogs. Refraining from using robotic lawn mowers at night is a simple and effective way to help protect this specially protected species.