Harvest mice are Britain’s smallest rodents. They are rarely seen in the wild but their summer breeding nests are easily recognised, being balls of woven living grass built among stalks. The mice themselves are tiny, small enough to fit in a matchbox, with golden brown fur. Once considerably more common in Britain than they are today, harvest mice have suffered from habitat loss and the changes to traditional farming practices in modern times.
Harvest mice are found across Europe, except for Scandinavia, and also in parts of the Far East. In Britain, they are found in England, south of Yorkshire, and although there are isolated records from Scotland and Wales, these are probably from the release of captive animals. Harvest mice are not found in Ireland. They live in hedgerows, reed beds and other areas of dense vegetation, such as tall grasses and cereal crops. They eat seeds, insects such as aphids, blackfly and caterpillars in summer and fruit such as blackberries and rosehips in autumn. Harvest mice may be active both day and night, although they are most often active at dusk. They do not hibernate in winter but they spend most of their time underground so they are unlikely to be seen. In the summer, breeding nests can be found in long grass, reed beds, hedgerows and of course, amongst crops. Males can have a territory of up to 400 square metres; female territories are smaller. Harvest mice have many predators, including foxes, owls, stoats, weasels, cats, crows and kestrels. Harvest mice can live for up to 18 months but often it is no more than 6 months.
Modern farming methods have not been good for the harvest mouse. Huge amounts of hedgerow have been removed from the British landscape, reducing the habitat available. Harvest mice need somewhere sheltered to construct their winter nests and hedgerows are very important for this. Grassy field edges are important habitat for harvest mice and these are often reduced due to close ploughing. With the loss of so much habitat in the form of hedgerows and harvest fields, roadside verges are increasingly important habitat for harvest mice. At present, harvest mice are not legally protected in Britain, except for the general protection afforded by the Wild Mammals Protection Act (1996).