Mouse Ecology Project: Research Techniques

We’re using a variety of techniques to monitor mouse populations and gather data about mouse activity and food resources in grain production systems.

Capture-mark-recapture

We set up live-capture traps in paddocks for 5-6 nights to catch mice. Mice are measured and weighed, their reproductive status assessed, a DNA sample collected, and are given a unique PIT tag ‘microchip’ to identify any individuals recaptured on subsequent nights. This information tells us about mouse population size and density within paddocks. It also helps us to understand the age structure of the population, whether breeding is occurring or has occurred, and provides insight into the health condition of mice. Regular trapping at various growing stages (crop sowing, ripening, harvest, post-harvest) is important for monitoring mouse population dynamics in paddocks over time.

Burrow counting

Working within one hectare we mark mouse burrow entrances with cornflour to determine the following day whether the burrow is active. We use a GPS to record burrow locations for later spatial mapping. The number and density of active burrows is an indication of mouse activity within paddocks. Counting burrows throughout the growing season tells us how mouse activity and resources in a paddock change over time.

Radio tracking

By attaching tiny radio transmitters (<0.80g) to mice we can monitor their movement and location within paddocks. A location fix collected during the day tells us where the mouse’s home burrow is and by collecting several location fixes throughout the night we get an idea of the home range of individual mice. This can tell us how far mice are moving to find food.

Spool-and-line tracking

We attach a small cotton thread spool (<1g) to mice and release them back into the paddock at dusk, attaching the loose end of the cotton thread to a plant stem so the spool unravels leaving a ‘trail’ behind the moving mouse. The following morning the 50m of thread has been dispensed by the moving mouse and the trail is recorded spatially with a GPS. The spool casing falls off the mouse within a few days. This technique provides very fine scale data about mouse movement in paddocks, including habitat and burrow use.

Giving up density (GUD) trays

These are small trays set up in paddocks containing a known number of seeds or grain (food for mice) buried in a sand matrix. The number of seeds/grain eaten by mice indicates their willingness to spend time foraging for food in the open (both indicators of food availability in paddocks and the risk of predation during searching for food). This information provides a measure of “predation risk”, or at what point to mice “give up” feeding because of the risk of predation.

Biomass sampling

By sampling crop biomass we can quantify the amount of residual grain or food available to mice before and after harvest, and whether this food availability changes spatially within paddocks over time.