Rodents are a key component in the healthy functioning of many ecosystems, such as grasslands and woodlands. They provide food for lots of species, from birds of prey to larger mammals. Rodents also produce lots of young every year, so must have ample food available for them – usually seeds, fruit and small insects. Whenever rodent populations dip, there are knock-on effects across the habitat.
There are 14 species of rodent commonly found in Britain, including rats, squirrels, mice, voles and, more recently, the beaver. One of the least familiar of these is the harvest mouse, Britain’s smallest rodent, which we will take a closer look at here.
Harvest mice are not especially fussy, and are happy anywhere there are ample stems for them to clamber up. Very rarely do they come down onto the ground if they can avoid it. They are tiny creatures, around 6cm long, with a tail close to the same length. The long tail is used to help with balance and climbing. They react quickly to any disturbance, quickly disappearing back into the vegetation in response to nearby noises.
Harvest mice are thought to be fairly widespread, but are actually very difficult to find. Their
presence is mostly picked up by the signs they leave behind – like their intricate nests. The nests are carefully woven from grass and leaves within dense vegetation, at least 10cm above ground, so even these are difficult to spot! Harvest mice adapted themselves to farmed habitats by creating their nests in crop fields such as wheat and barley, but modern combine harvesters have caused a new threat. When fields were hand-cut, the mice could easily run to the safety of field margins, but modern machinery does not give them the time to escape. They also build their nests and live in verges, reedbeds and grassy hedges – all of which habitats have been lost in many areas as green spaces are developed and wetlands drained.
Recent studies have helped to shine a light on this elusive mammal, but more must be done to protect the harvest mouse. They seem to be able to respond quickly to changes in habitat, as long as the habitat is connected to others and buffer zones are present between developments and their living space. Reintroductions can work well, as the mice are relatively easy to breed, and once conservation efforts are in place they seem to breed and colonise the reintroduction area quickly. The more we learn about marginal habitats like road verges and field edges, the more they are shown to be important for all sorts of
wildlife, including our smallest rodent.
To find out more about your local wildlife, visit the Trust’s website: hiwwt.org.uk