Harvest Mice

The harvest mouse (Micromys minutus) is one of the smallest rodents in the world, and the smallest in Britain. This tiny, gingery mouse lives in tall grasses and reeds across Europe and Asia, where it climbs stems using its gripping tail and weaves amazing ball-shaped nests high above the ground.

Scientific Classification & Quick Facts

Common name	Harvest mouse
Scientific name	Micromys minutus
Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Rodentia
Family	Muridae
Genus	Micromys
Conservation status	Least Concern
Type	Tiny rodent; very good climber
Diet	Insects, seeds, berries, fungi, moss and roots
Habitat	Tall grass: reed beds, hedges, cereal fields, verges
Native range	Britain, mostly south of central Yorkshire
Size	50-70 mm long
Colours	Russet-orange fur; white underside
Special feature	Grasping tail; builds a new nest for each litter

Anatomy

A harvest mouse weighs just 4 to 6 grams, about the same as a British 20p coin or an American quarter. Its body is only about 5 to 7 cm (2 to 3 inches) long, and its tail is roughly as long again.

Compared with other mice, it has a short, blunt nose, small eyes and small, hairy ears. Its fur is russet-orange on the back and white underneath. Its most special feature is its prehensile tail: the tip can wrap around grass stems like an extra hand, helping the mouse balance and climb.

Behavior

Harvest mice are expert climbers. They scramble through the “stalk zone” of tall grasses, reeds and cereal crops, gripping stems with their feet and tail. They can be active at any time of day or night, but are often busiest around dawn and dusk.

Because they are so small, harvest mice lose body heat quickly, so they need to eat a lot for their size and are almost always on the move looking for food. They have sharp hearing and react instantly to danger, freezing or dropping to the ground if a predator such as an owl, weasel or cat comes near. Unlike dormice, they do not hibernate. In winter they move down to ground level, sheltering in tussocks, burrows, hay bales and stacks of straw.

Habitat

Harvest mice are found from Britain and western Europe all the way across Asia to Japan. In Britain they live mainly in England, especially in the south and east, with only scattered records in Wales and Scotland.

They need places with tall, dense grasses, such as reed beds, field margins, roadside verges, hedgerows, salt marshes, ditches, rough grassland and cereal fields. Here they build their famous summer nests: tennis-ball-sized globes woven from living, shredded grass leaves, still attached to the plants.

Breeding

In the wild, harvest mice usually breed between May and October, with a peak in August, and in mild years they may keep breeding into December. A female can have two or three litters a year. Cold, wet weather is hard on young mice, and many die in bad summers.

Each litter usually has around five or six babies, born after a pregnancy of about two and a half weeks. The young are born pink, blind and hairless, but they grow fast. They begin exploring outside the nest at about 11 days old and are independent at about 16 days. By then the nest is getting very scruffy, and the mother builds a fresh one for each new litter. Wild harvest mice rarely live longer than about 18 months.

As a Pet

Harvest mice are bred in captivity and are sometimes kept as pets or by schools and conservation groups. They are fascinating to watch, but they are tiny and easily stressed, so they are best for patient keepers who are happy to observe rather than handle. Always get them from a reputable breeder; never take mice from the wild.

Housing

A glass aquarium or terrarium works well, and because harvest mice are such agile climbers, a tall tank is better than a long, low one. A secure, fine mesh lid is essential, since they can squeeze through tiny gaps. Fill the tank with dried grasses, twigs and tall stems to climb, plus hay or soft grass for nest building. Keep the tank indoors at normal room temperature, out of direct sunlight and drafts; extra heating is not usually needed.

Food

In the wild, harvest mice eat seeds, grains, berries, fruit and insects, along with some moss, roots and fungi. They sometimes nibble cereal heads, but they do not cause serious damage to crops.

Pet harvest mice do well on a good-quality small-rodent or finch seed mix, with small amounts of fresh fruit and vegetables and occasional live insects such as mealworms. In summer they love exploring fresh natural branches, like a bramble cutting, seeding grass heads or the seed head of a hogweed plant. Provide fresh water at all times, and ask a vet who knows small rodents if you are unsure about anything.

Harvest mouse FAQs