Life in a variable world: response to commentaries

Abstract

I am grateful for the thoughtful commentaries on my article by so many colleagues, and relieved that the overall tendency has been to praise my arguments with faint damns. Here I shall simply pull together some of the key points. The review did not set out to be a comprehensive survey of behaviour environment interactions, which I acknowledged were even more complex than I was depicting. Lawrence emphasises this by suggesting that animals respond to whole situations (e.g. a nest site) rather than individual stimuli (e.g. enclosure of potential nest sites) and Nicol outlines some of the mechanisms important in the two aspects of such interactions-the environmental variation (which may indeed be categorized) and variation in the animals’ responses. I granted that animals do sometimes categorize in this way but maintain that variability in specific stimuli is also important, particularly in more artificial conditions. Wemelsfelder points out the additional aspect of temporal variation in stimuli, which I did not cover. I disagree with Newberry and Estevez’ semantic point that if supernormal stimuli are common in animal housing they are by definition no longer supernormal, especially in view of Toates’ reasonable call for formalized use of language. Some of my examples may of course be susceptible to other explanations, but my point remains that we have an incomplete understanding of animals’ responses to stimuli which vary on a continuum. Toates lucidly reminds us that we lack a framework for understanding not just responses to such stimuli but all complex behaviour-a concern echoed by Curtis. Toates goes some way to providing such a framework-and of course has done much more along these lines elsewhere. Other approaches which may contribute are mentioned by Fraser (resource defence theory) and Newberry and Estevez (stochastic dynamic modelling). Curtis, Mend1 and Newberry and Estevez emphasise, reasonably enough, that we need more descriptive knowledge of the biological phenomena involved. Wemelsfelder provides an additional perspective in stressing that stimuli are not just received but also sought: concentrating on the animal will give us different conclusions from concentrating on the environment.