Impacts and management of mice in pasture-cropping systems

 

This NSW DPI (Department of Primary Industries) funded three-year project (2022-2025) aims to increase our understanding of house mouse ecology and biology in the cropping-pasture systems of NSW.  

 

The 2021 mouse plague through much of northern and western NSW demonstrated that pasture is a significant component of farming systems in these regions in the context of managing mice. Grazing (native and mixed pastures) accounts for 68% of land use, with the rest largely dryland agriculture, and farmers report that pastures are playing a significant role in sustaining mouse populations. These pastures hold a diverse range of perennial and annual grasses and forbs (weeds and legumes) all of which may provide food and shelter for the pest house mouse. They may also harbour additional animals (predators and/or competitors) that are not present in crop monocultures. The prevalence of these non-crop habitats makes management recommendations based on previous research undertaken in the southern Australian state’s cereal-monoculture areas less applicable.

We sincerely thank the farmers for letting us access and undertake this research on their properties.

 

Our Research Questions

In a collaboration between CSIRO and NSW Department of Primary Industries, we have established research sites at Trangie and Coonamble in western NSW to study how extensive areas of pastureland adjacent to cropland influences the behaviour, breeding and survival of house mice. We will use several methods to trap and monitor house mouse populations over time. Understanding how house mice use pastures and the role these habitats play in sustaining house mouse populations is critical to optimising management efforts and to reduce the damage to adjoining crops.

To determine the extent of pasture use by mice and their relationship to crop dynamics, we will:

1. determine if pastureland acts as a source for house mouse populations invading crops,
2. determine the timing of house mouse movements (if any) from pastures to crops, and
3. develop management recommendations for farmers in this pasture-crop system.

 

 

Our Research Activities

Mouse trapping commenced in August 2022 to estimate population densities, timing of breeding, and movement between pasture and crops.   

Mouse populations, thus far, have been observed to be geographically patchy but in some places high in late winter. Pregnant females were captured, confirming that breeding had started. 

However, continued rain events and flooding during spring of 2022 appeared to cause house mouse nests to become inundated with water, likely killing any nestlings, as very few juveniles were observed during population surveys at this time. As a result, on the Trangie sites, populations were lower in spring than they had been in winter. Finally the rain ceased and trapping in January 2023 has revealed that many mouse populations survived the flooding, are continuing to breed and recruit young individuals into the populations.  These young of the year are breeding also.  With so much food around – seeding grasses and invertebrates – there is increased potential for mouse numbers to increase dramatically towards the autumn sowing season.

To gain a better understanding of how house mice use pasture and crop landscapes, we will investigate the times and locations that they are active relative to location considering distance from unsealed roads or tracks, the habitat structure, the land-use type and temperatures, and the distance to predators and/or competitors. Foraging behaviours of house mice under these varied conditions will also be observed to determine their risk sensitivity and what role stressors could play in house mouse population management guidelines. To gain this information we will use tracking tunnels, infra-red motion-sensing cameras, and a known introduced food source (peanuts). This research will help us to understand how mice use different habitats, and respond to stressors of predators and competitors, which will allow us to better direct how and when mice population management should proceed.

 

We would like to acknowledge the Traditional Owners of the lands that we are privileged to work on: Wiradjuri (Trangie) and Gamilaraay and Wailwan (Coonamble) lands.