Britain's smallest rodent, the harvest mouse, has declined dramatically with changes in agricultural practice. Understanding their welfare and habitat needs guides conservation.
Harvest mouse welfare is tied to the quality and diversity of their grassland and field margin habitat. These tiny mammals are thermally vulnerable - their small body size means they lose heat rapidly, making adequate shelter and food availability critical for survival, particularly for overwinter juveniles. Loss of tall grass habitat removes both the structural complexity they need for nest building and the invertebrate food they require for breeding. Creating tall grass margins with diverse plant species is one of the most direct harvest mouse welfare interventions available to farmers and land managers. The species is also a useful indicator of field margin quality - populations track habitat welfare for a wide range of invertebrates and farmland wildlife.