The Effects of a Natural Increase in Food-Supply on a Wild Population of House Mice

Changes in density and breeding of the house mouse (Mus musculus) in a New Zealand forest dominated by hard beech (Nothofagus truncata) were monitored for 2.5 years. Mice bred during winter and increased dramatically in density only during a beech mast year. Mice readily ate the endosperm and embryo of hard beech seed in die laboratory and chemical analysis showed it to be a very nutritious food source, similar in quality to Fagus beech seed in the northern hemisphere. Thus the mouse, introduced to New Zealand, responds to a Nothofagus mast year in a similar way to other rodent species in the northern hemisphere during a Fagus mast year.