Behavioural biologists have typically combined interests in the control, function, development and evolution of behaviour. They have used observational and experimental methods, and their findings have been both attractive and scientifically invigorating. A future to be hoped for is that they will continue to combine an understanding of behaviour with studies carried out at other levels but that they will not become too locked into a purely analytical framework. Methodologies are needed that enable scientists to deal with all the principal factors that influence behaviour. In so doing, behavioural biologists should be able to retain a grasp of what is to be an intact, freely moving animal. I believe that the late Günther Tembrock, to whom this paper is dedicated, would have approved of such a systems approach to behaviour.