A method for controlling a robot arm arranged to bring animal operation device to a specific position relative to an animal body part, the robot arm being controlled to maintain a certain position relative to the animal body part during the animal-related operation, the robot arm being controlled not to perform a movement unless the body part lies outside a tolerance range around a current position of the robot arm, wherein the boundaries of the tolerance range are determined repeatedly in dependence on at least the current position and the current speed of the animal body part. Hence, the tolerance range is dynamic, and dependent on the measured movement of the body part or body part reference point. By taking such movement into account, it has proved possible to reduce robot arm movements, both in number and in covered distance. The invention also provides an implement arranged to perform the method.