The temporal pattern of feeding over the oestrous cycle of the mouse.

The detailed temporal pattern of feeding in female mice was measured by an automated method over the oestrous cycle whilst feeding on either of two foods differing in stimulus characteristics, but of similar calorific value. The total time spent feeding varied systematically over the cycle, being increased for sweet food and decreased for laboratory chow at the time of sexual receptivity. and increased for both foods towards the end of the cycle. The temporal pattern is analysed into a number of variables, which are seen to alter in different ways over the oestrous cycle. The pro-oestrus disturbance is due to alterations in meal size brought about solely by changes in mean bout length, themselves products of variations in the initial bouts of the meal. Inter-meal interval is unrelated to changes in meal size at this time, allowing the latter to affect food intake. The changes towards the end of the cycle are produced by alterations of meal frequency at constant meal size. It is argued that separable 'phasic' and 'tonic' effects of reproductive condition on feeding may therefore be identified, and that they might possibly have different functions.