Scurrying through dry leaf litter or behind kitchen skirting board, house mouse is ultimate opportunist of New Zealand landscape. "Micro-predators" of ecosystem. Possessing level of versatility allowing survival in environments ranging from freezing heights of Southern Alps to dry interiors of coastal dunes. Heart beats hundreds of times per minute. Metabolism demands constant fuel. Creatures of perpetual, nervous industry. Small size is greatest asset. Allowing exploitation of food sources and hiding places inaccessible to larger, more obvious rats. Social life of mouse is frantic cycle of reproduction and exploration. Can begin breeding at just six weeks of age. Leading to population growth more like biological explosion than gradual increase. "Boom-and-bust" cycle most visible during "mouse years". Forest floor literally vibrates with movement. Begin to spill over into human dwellings in search of space and sustenance. Sheer numerical weight makes them significant competitor for native wildlife. Can strip forest of seed-bank. Consume vast quantities of invertebrates forming base of food chain. While often seen as mere nuisances in domestic setting, impact on New Zealand’s unique biodiversity is profound. Known to attack eggs of small birds. Documented preying on native skinks and geckos. Proving being small does not mean being harmless. In forest ecosystems, also serve as "prey-switch" for larger predators like stoats. When mouse population crashes after peak, hungry stoats turn attention toward native birds. Creating secondary wave of destruction echoing through canopy. In national consciousness, house mouse is "unwanted roommate". Creature followed us into every corner of country. Mastered art of living in gaps. Surviving on crumbs of civilisation while maintaining wild, resilient core. Represent complexity of island ecology. Where even smallest introduction can have massive, cascading effects on survival of ancient lineages. Reminder that in battle for conservation, it is often most inconspicuous players proving to be most persistent challenges to balance of land. No one told it otherwise.