Mice are a key food source for stoats and feral cats in New Zealand forests. When food is abundant, their numbers can increase rapidly, but that doesn’t neccessarily equate to less risk for our native species.
As omnivores, mice eat both plant and animal matter. They adapt easily to available food, with invertebrates making up most of their diet. However, they also eat bird eggs, chicks, lizards, and have been recorded feeding on inanga eggs in estuaries – impacting whitebait runs.
Their wide-ranging diet leads to broad ecological impacts. By consuming insect larvae that break down leaf litter, mice disrupt nutrient cycling and prevent nutrients from returning to the soil. They also target specific seeds, limiting regeneration and altering forest composition.
In mast years – when plants like beech trees and tussocks seed heavily – mouse populations boom. This fuels a rise in predator numbers. As predators switch from mice to native species, bird predation spikes and can lead to local collapses in native populations.
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