Lithuanian lore:

Indoor Snakes

Control of fieldmice in granaries were always a problem for farmers. Before house cats became widely available, Lithuanians used grass snakes for rodent control in places where they stored their grain. Christian missionaries, not speaking the local language, jumped to the conclusion that the snakes kept indoors were some kind of objects of the Lithuanian pagan religion. In truth, good mouse traps were harder to find than grass snakes, yet grass snakes are not dangerous to humans and are efficient rodent predators. (Click here to read more Lithuanian lore.)