Pest Guides

Field Mouse

Apodemus sylvaticus


Image of field mouse (Apodemus sylvaticus)

  • The head and body of an adult Field Mouse is 80 – 100mm in length; where its tail is 70 – 90mm.
  • A male field mouse can weigh up to 25g, whereas the weight of a female field mouse is around 20g.
  • The fur of Field Mice is sandy / orange brown on their head and back, yellowish on their flanks and white on their bellies. A small streak of yellow is noticeable on their chest.


  • Their lifespan averages two to three months, but they can survive as much as 20 months in the wild, or two or more years in captivity.
  • The breeding seasons are March/April to October/November and gestation lasts approximately 25 days. They grow their first fur after six days; their eyes open after 16; and they are weaned at around 18 days old.
  • Survival of the young and adults is poor during the first half of the breeding season as adult males can be aggressive towards one another and to the young, who are then driven from the nest.


  • A field mouse eats a high proportion of the seed crop of trees such as oak, beech, ash, lime, hawthorn and sycamore.
  • Small snails and insects are particularly important sources of food in late spring and early summer when seeds are least available and larval and adult insects are plentiful.