Population dynamics and behaviour of a founder population of house mice

Abstract

The house mouse is a highly adaptable and widely distributed species which has significant impacts on ecosystems where it is invasive. Despite a vast body of literature on the ecology and physiology of the house mouse, little is known about the mechanisms of mouse colonisation of new environments. The purpose of this study was to describe the population dynamics and spatial behaviour of house mice in the process of island colonisation. An experimental population was established from a single founding pair on Saddle Island, in the Hauraki Gulf, New Zealand, simulating an island invasion. The population was intensively studied over an eight month period in order to: investigate the rate and pattern of population growth from the arrival of the founder pair; describe the movement and social structure of the population at different population densities; and investigate the detectability of mice, particularly at low population density. Data from previous mouse releases on Saddle Island (J. MacKay, University of Auckland, unpublished data) were also used in some analyses. The experimental population grew to a peak density of 10 mice ha-1 within five months of the founders' release. Initially, population growth followed a classic logistic growth pattern, but with the onset of winter, seasonal weather became the most important factor regulating population growth. Upon incursion on the island, the population founders ranged widely. Average home range size decreased dramatically once the population was established and remained stable for the remainder of the study. Although analyses of social structure were inconclusive, it was considered most likely that the experimental population maintained a non-territorial social structure. Mice were highly detectable using selected standard methodologies, even at low population density. Unexpectedly, however, males were found to be less detectable than females during the first few days after incursion. The overall conclusion of this thesis is that house mice can rapidly establish populations of sufficient density to have negative impacts on native biota and ecosystems. Therefore, to prevent the establishment of stable invasive mouse populations, frequent surveillance of mouse-free areas and swift deployment of contingency measures upon detection are necessary. The study documented in this thesis was the first to follow a house mouse invasion from the initial incursion phase through to establishment of a viable population. As such, it represents an important advance in the study of the colonising behaviour of this prolific invader.