Abstract:
House mice inhabit a variety of habitats on Marion Island, with the density of mice varying according to vegetation type and invertebrate biomass, and highest mouse densities occurring in biotically influenced areas. The density of mice fluctuated seasonally, peaking towards the end of summer. The reproductive season lasted ff,7 months, and was apparently regulated by the relative availability of food which mainly affected the reproductive activity of the females. The age structure of the population varied during the year, with no sex related mortality factors being observed. The mice, in the approximately 100-150 years that they have inhabited the island, appear to have adapted physiologically to this harsh climate, by having enlarged kidneys and adrenals, an increased amount of brown adipose tissue, and being in general larger in size. Mice ate predominantly invertebrate material throughout the year, with plant material occurring mainly during the summer months. The larvae of the flightless moth PringZeophaga marioni was the most important prey species.
