Habitat: Harvest mice live in tall grass, grain fields, vacant lots, and along roadsides. During severe winters they sometimes seek shelter in sheds and houses. The male roams over a territory of approximately 500 square yards, while females have smaller territories. In summer they are active at night, but in winter they are active during the day. 

Food and Feeding: The harvest mousse eats seeds, fruits, berries, and insects such as moths, grasshoppers, and caterpillars. What it eats depends on what is available during each season. Although grain is one of its main foods, the mouse compensates somewhat for any damage it may do to grain crops by eating the pests that threaten those crops. Wheat aphids, such as blackfly, secrete a honeydew that harvest mice eat. To feed on grain, the tiny harvest mouse climbs up the stalk to the seed head. It uses its prehensile (adapted for holding) tail to grip the plant stalk and to balance itself. Then it breaks off a seed by grasping it in its teeth and moving its head with a sideways motion. It holds the seed in its front paws, removes the husk, and gnaws into the center of the seed. Harvest mice feed on blackberries when they are in season. They like the sweet taste of the fruit.

Breeding: Harvest mice breed from May to early October, often producing three litters of three to eight young in a single year. The newborns stay in the nest for 11 days, where they grow rapidly. The mother leaves to search for food but returns at regular intervals to feed and clean the young. She eats droppings so that predators are not attracted by the smell. At two days old the young mice can push themselves around the nest. Four days later they start grooming themselves, and by the eighth day they can see clearly. At nine days they have teeth and begin eating solid food; at 10 days, the mother begins to wean them. The young are fully independent two weeks after birth. The mother is usually pregnant again by this time, and she abandons her litter to look for a new nesting site. The young remain near the nest for several more days and then leave to find territories of their own.

Naturewatch: Evidence that an old world harvest mouse is nearby can be found by looking closely among tall grasses and most crop fields except barley. Its nest of shredded grass and leaves is wedged between plant stems and attached to them, usually one to two feet above the ground. The nest is well hidden in summer when the vegetation is lush, but it is easier to spot in late fall and early winter when the plants lose their leaves.

Key Facts:
Sizes:
Length: Head and body, 2-3 in. Tail, 2-3 in.
Weight: Adult, 2 oz.

Breeding:
Sexual maturity: 45 days
Mating season: May to October
Gestation: 17-19 days
No. of young: 3-8 per litter. May have 3 litters a year

Lifestyle:
Habit: Solitary. Active at night in summer and by day in winter
Diet: Mainly seeds and insects, also some fruit
Lifespan: In the wild, up to 18 months, but usually 6 months. Up to 5 years in captivity

Related Species: Although it belongs to the same family as other mice, the old world harvest mouse is the only species in its genus.
Distribution: Throughout Europe and northern Asia.
Conservation: Although not endangered, numbers have been greatly reduced by modern agricultural methods, such as combine harvesting, spraying, and stubble burning.

The Harvest Mouse’s Nest: The nest of the harvest mouse is built by the female. Balancing one to two feet up a grass stem, she bends and weaves the long leaves growing from the stem to form a framework for the nest. She then weaves pieces of grass among the leaves, forming a rounded structure three to four inches in diameter. She covers the entrance with grass after the young are born.

Did You Know: 
American harvest mice, like old world harvest mice, build their nests on grass stems.
The old world harvest mouse is the only mammal in Europe with a tail that is prehensile – that is, adapted for seizing and grasping.
In the wild, pregnant females drive away the males, whereas in captivity, they tolerate their presence.
In parts of Europe, harvest mice have been found living in ham curing rooms and larders, earning them the name “bacon” mice.

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