Does the house mouse self-regulate its density in maturing sorghum and wheat crops?

Area of Science:

• Population ecology
• Pest management
• Agricultural science

Background:

• Understanding population regulation is key in ecology and management.
• House mouse (Mus domesticus L.) populations exhibit occasional eruptions in Australian grain-growing regions.
• The self-regulatory mechanisms of mouse populations in maturing cereal crops require investigation.

Purpose of the Study:

• To determine if house mouse populations are self-regulated in maturing sorghum and wheat crops.
• To assess the relationship between initial mouse density and density at harvest.
• To evaluate the role of food supply (grain yield) in population dynamics.

Main Methods:

• Experimental introduction of eight initial mouse densities (D(I)) into mouse-proofed pens containing sorghum and wheat crops.
• Measurement of density at harvest (D(H)) after 49 days.
• Analysis of the relationship between D(I) and D(H) in relation to available grain yield.

Main Results:

• Abundant grain supply (≥1.85 tonnes/ha sorghum, ≥3.11 tonnes/ha wheat) was available to mice at harvest.
• The relationship between D(I) and D(H) followed an asymptotic exponential curve, with density saturation around 3100 mice/ha at higher initial densities.
• Increased recruitment of young mice at lower initial densities contributed to density saturation.

Conclusions:

• Mouse densities in cereal crops are influenced by a numerical response to grain availability, modulated by an unknown self-regulation mechanism at higher densities.
• This mechanism, possibly related to spacing behaviors, reduces the numerical response at high densities.
• The developed model is valuable for predicting mouse population increases and eruptions in cereal crops, potentially informing control strategies.