DIET OF THE HOUSE MOUSE, MUS-DOMESTICUS, IN THE MALLEE-WHEATLANDS OF NORTH-WESTERN VICTORIA

The quality and/or quantity of food available to mice at key times may be important in generating plagues. This study examined the diet and breeding performance of mice over two years in the mallee wheatlands of Victoria. Mice were trapped approximately every 6th week and their stomach contents examined for seven categories of food. Indices of occurrence and estimates of percentage volumes of each category indicated that cereal seeds were the staple food of mice. They bred earlier in the second year, but in both years there was a pulse of invertebrates and fresh grass seeds in the diet before the onset of breeding. These pulses occurred when seed reserves ['mature' (> 3 months) cereal and dicotyledon seeds] were low. Mice, however, were highly responsive to changes in the availability of different food classes throughout the study. Thus the relative influences of nutritional factors (food quality) and availability of food (food quantity) on the onset of breeding were difficult to determine. The annual peak in female breeding coincided with the availability of fresh cereal grain. Breeding ceased in autumn each year despite the presence of ample 'mature' cereal seeds. Investigations of the effect of climatic factors on timing and abundance of nutrients in the environment is essential for an understanding of their influence on the population dynamics of mice.