Strolling through grasslands, elevated at least 30cm off the ground, you may spot a spherical nest tightly woven by grass. These carefully crafted little nests belong to Europe’s smallest rodent – the harvest mouse.

To support the nest, a robust central structure is needed – for example, common reed works well. It is the female harvest mice that will build the nest, which is usually between 8-12cm in diameter and is used solely to shelter her young.

The female harvest mice can be pregnant 2-3 times a year and will build a new nest each time, often close to their previous shelters. Gestation takes around 18 days, and babies are born smaller than your little fingernail. The average litter will have five babies, each born blind and hairless.

Babies develop very quickly and around the 11th day the young will venture outside the nest with their mum. At about 45 days of age, harvest mice start to breed, usually from June and peaking in August.

Their tiny head and body measure 50-70mm, and they have a prehensile tail which they use as a fifth limb to wrap around stems to aid nimble climbing. Small, rounded and hairy ears, a blunt nose, pure white underside and russet-orange hair on top is the makeup of these marvellous little mice.

Where do they live?

In the UK, harvest mice tend to live in the southern regions and are often hard to spot. These rodents prefer undisturbed areas like hedgerows, roadside verges, cornfields, grasslands and other densely vegetated areas to make for excellent protection. They are also omnivores and love to feast upon seeds, fruit, moss, fungi, wheat, flies and caterpillars.

The average lifespan of harvest mice is around 18 months, but survival for these little mice is challenging. Sadly, most die off during the winter months due to the change in climate and competition for food. They maximise their chance of survival in cold and wet weather by building a nest at ground level. They are also highly preyed upon by owls, hawks, cats, crows, weasels and other wildlife. Baby harvest mice have also been known to be caught by toads and blackbirds.

Spare a thought for the smaller creatures

Harvest mice are thought to be in decline. As they nest out in the countryside, there are of course other threats to their mortality, such as: cutting back hedgerows which they rely on for shelter, field ploughing, use of pesticides, and flooding. Harvest mice are very adaptable animals and do not rely on any particular plant species, however, mowing grasslands in late summer can be devastating for them.

The main thing they need to thrive is good winter cover and access to food. You can help harvest mice, especially if you live in the countryside, by letting hedgerows grow a little thicker and by leaving some long grass around field margins during winter, so these often overlooked little creatures have shelter during the colder months and a greater chance of survival.