Abstract

The diet and breeding seasons of house mice, Mus musculus L., were monitored for 16 months in six habitats on two cereal farms: fields of barley, wheat, sorghum and rice stubble, and contour banks in rice fields, and channel banks. In all habitats mice were mainly granivorous. Because of rotational cropping and irrigation, seeds were available in different habitats in each season and this was reflected in the diets. Cereal grains spilt at harvest and other stale seeds were the main food in the nonbreeding season. It is proposed that the low quality of this food limited breeding. When milk-ripe grass seeds became available, mice switched to this fresh food, and started breeding about 1 month later. The onset of breeding was asynchronous between different habitats; this suggests that time of onset of breeding was determined by availability of food.