Population regulation and dispersion of the smoky mouse, Pseudomys fumeus II. Spring decline, breeding success and habitat heterogeneity

The smoky mouse (Pseudomys fumeus) undergoes large annual fluctuations in abundance, characterized by a dramatic decline in numbers just before the summer breeding season. The population on Mount William has two components which are differentially affected by this decline. The first, consisting of animals living in preferred microhabitat, have high breeding success and are unaffected by the decline. Females normally breed in two seasons, and in the second season breed earlier than first year females. The second component lives in non-preferred microhabitat, is severely affected by the decline and shows high levels of fighting during the decline period. This difference may result from the lack of high quality food resources in non-preferred microhabitat following the seasonal cessation of production of fungal sporocarps. The role of spatial and temporal heterogeneity in the availability of food resources in the population processes of small mammals is discussed.