The harvest mouse, the world's smallest rodent, weaves intricate tennis-ball nests in grass stems. With population declines linked to agricultural intensification, its welfare depends on rough grassland and hedgerow habitats.
Harvest mouse welfare is affected by loss of rough grassland, reedy vegetation and traditional cereal margins. Combine harvesters and grass cutting machinery destroy breeding nests and kill adult mice. The shift from spring to autumn sowing of cereals has reduced the stubble habitats harvest mice use for winter refugia. Grassland improvement that eliminates rough margins removes both breeding and feeding habitat. Nature reserve management and agri-environment scheme habitats — particularly uncut grass margins and rush pasture — support harvest mouse populations. Nest box schemes using artificial semi-spherical boxes have shown some adoption success. The harvest mouse's small size and cryptic habits mean population trends are poorly monitored compared to the conservation attention warranted.