Harvest Mouse - Micromys minutus

The harvest mouse is one of the world’s smallest rodent weighing only 6 g when adult. As they are so tiny, they can climb fast and easily up thin stems of grass without it bending. As the name suggests they were often found in cornfields but are more likely to be found in the long grass at the base of hedges and benefit from the large areas of tussocky grass now found alongside motorways. It is the only mouse that can build nests of woven from grass and vegetation around the stalks of plants about 18 “ high although nests can also found at ground level. Breeding nests are nearly double the size of non breeding ones. In the wild, they would produce around three litters a year although in captivity, this can be as high as 8.

The adults have a reddish brown coat whereas the youngsters are brown and easily recognised. They climb stems of plants using their prehensile tail as a fifth limb. These mice are usually found in long grass during the summer and move into grassy tussocks or rushes for the winter. Meadows or pasture where the grass is only cut once a year is suitable habitat. Farming practises such as cutting grass for silage and spraying against insect damage have led to the decline of these tiny rodents. Tennis balls attached to a cane have been used in the wild to attract field mice for nesting to enable monitoring of a wild population.

The diet of the harvest mouse ranges from seeds, fruit and insects. They will also eat buds and some flowers. As they are predated their lifespan would be a maximum of 18 months but eaten by foxes, owls, domestic cat, hawks and corvids, they would be very lucky to reach this age.

They are very territorial and the females will often harass the males. Once paired, the female will become pregnant for a period of 19 days with a litter of anything from 1 to 8 babies ( who are  minute – 0.6 to 0.8 g at birth ). The mother suckles several times a day. By day 4 the pink babies start to grow fur, their teeth erupt on day 7 -8. Belly is white by day 8 – 9 which is also when their eyes open. By 14 days they start to eat solids and are abandoned by 15 – 16 days of age.

Secret World Wildlife Rescue keeps unrelated harvest mice in breeding tanks and the young produced are released at Secret World in their Millennium Wood. In 2008 we have released over 60 youngsters.