Abstract
Under natural conditions, many aspects of the abiotic and biotic environment vary with time of day, season or even era, whilst these conditions are typically kept constant in laboratory settings. The timing information contained within the environment serve as critical timing cues for the internal biological timing system, but how this system drives daily rhythms in behaviour and physiology may also depend on the internal state of the animal. The disparity between timing of these cues in natural and laboratory conditions can result in substantial differences in the scheduling of behaviour and physiology under these conditions. In nature, temporal coordination of biological processes is critical to maximise fitness because they optimise the balance between reproduction, foraging, and predation risk. Here we focus on the role of peripheral circadian clocks, and the rhythms that they drive, in enabling adaptive phenotypes. We discuss how reproduction, endocrine activity and metabolism interact with peripheral clocks, and outline the complex phenotypes arising from changes in this system. We conclude that peripheral timing is critical to adaptive plasticity of circadian organisation in the field, and that we must abandon standard laboratory conditions to understand the mechanisms that underlie this plasticity which maximises fitness under natural conditions.