The mouse map

The harvest mouse is the smallest and least known of all British rodents, mainly because it is so difficult to find. A five-year citizen science survey in Kent is revealing valuable new information.

- Amy Jane Beer

Ecologist Steve Kirk has a nose for harvest mice – or, more precisely, for the places they live. “You can be driving along with him,” says Suzanne Kynaston of the Wildwood Trust, “and he’ll suddenly shout ‘Stop the car!’ and jump out, and within minutes he’s found a nest in the verge.” It’s a remarkable skill: harvest mouse nests are notoriously difficult to find. Woven from living strips of leaf blade, they are beautifully camouflaged. But Steve insists there’s no trick to it, just a keen eye and insight honed by years of experience.

The popular image of the harvest mouse is of a tiny creature clinging to a stem of golden wheat, but the species’ natural habitat is long, grassy vegetation and reeds, such as might be found in rough pasture, scruffy margins, wetlands and ditches. As grass-stalk zone specialists, they spend their lives clambering from stem to stem – feeding, sleeping and breeding without ever needing to descend to the ground. In the days of less intensive agriculture, arable land was an extension of this natural habitat, and the mice were most often seen fleeing to the safety of field margins when crops were cut by hand – a scene described by 18th-century naturalist Gilbert White, who documented the natural history around his rural parish in Selborne.

Changes in agriculture mean crop fields are now seldom the haven they once were – and the mice that do venture into them are much less likely to survive the onslaught of a vast combine harvester. Meanwhile, many former wetland habitats have been converted to farmland or urban sprawl.