The smallest of all native rodents is day-active and lives hidden from view in the open countryside. It prefers living spaces like grassy sedgemeadows and sedgestands, sometimes they settle in cornfields. Harvest mice clever climb in high grass or on plants. In contrast to the other mice they build nests, which are similar to bird's nests. They build loose sleeping nests with two entries as well as solid breeding nests with only one entry. Upto 7 times a year 2-6 youngs are born by one female. The youngs are sexually mature after 1 upto 1 1/2 months.

The main food of the harvest mice are seeds of the high-grass-zone and therein living insects. They overcome even big insects as the Green Grasshopper. The share of animal food increases in the wintertime. They clever lay bare in the stems of reed living insect larvas.