Locally common but thought to be declining
Harvest mice are the smallest rodents in Europe and the only British mammal to have a prehensile tail, able to grasp plant stems as they move through long vegetation. They have a reddish-yellow coat with a distinct white underside, small hairy ears and a much blunter nose than other mice. They are mostly nocturnal, although are active during the day in warm summer months. They build several grass nests throughout a season, for breeding, sleeping and resting. Harvest mice are less active in winter but do not hibernate; they stay close to the ground for warmth and insulation, and store food to sustain them through the winter months.
Head-body length: 5 – 8cm
Tail length: As long as the head and body
Weight: 5 – 11g
Lifespan: Up to 18 months
Harvest mice breed between May and October, producing several litters in a year. Litters of 3 – 8 pups are born after a gestation of 17 – 19 days, females give birth to 3 – 8 young. The young are weaned by about two weeks.
Grass seeds, fruit, berries, grain and sometimes insects in the winter.
Cornfields, hedgerows, reed-beds, brambles, long grass and sometimes open fields.
Barn owls, stoats, weasels and crows.
Severe winters and starvation; farming practices such as combine harvesting and stubble burning; and pesticides.
Status & conservation
Harvest mice were probably introduced to Britain after the last glaciation. They can be quite common locally, but nationally rare.
Population size & distribution
UK population 1,425,000. The population trend is unknown but it is thought that numbers have declined in the last 40 years and they are now rare. They mainly occur in southern and eastern England, with a few records in the Midlands, the north of England and southern Scotland. They are absent from Ireland.
Did you know?
Harvest mice shred grasses by pulling them through their teeth and use the strips to weave a hollow nest, about the size of a tennis ball, about 50 – 100cm above the ground and secured to grass stems.