An animal feeder includes a cover for a container and a detector for the presence or absence of an animal. A first cam has an operating surface which is an extension of an outer surface of the cover. A second cam has an operating surface which is movable according to the detected animal presence or absence. The first and second cam surfaces are engaged whereby movement of the second cam surface in first and second opposite directions respectively causes the cover to open and close the container according to the detected presence or absence of the animal.