Harvest Mouse, Micromys minutus

Harvest mouse specimen at the Museum of Zoology

Esme Ashe-Jepson, graduate student at the Musuem of Zoology, writes:

There is a curious specimen in the Museum of Zoology that is easy to miss, a small reddish-gold creature posed with its peculiar wire-thin tail wrapped around a stalk of wheat. Looking at this specimen you can imagine it racing through a beautiful golden summer meadow, surrounded by wildflowers and song birds, a quintessential summertime image. Even their name, ‘harvest mouse’ implies an undeniable connection to our arable landscapes, though you’d be just as likely to find one in a reedbed as a meadow. But chances are, you’ve probably never seen a harvest mouse in real life.

There are lots of reasons for this. Firstly, the harvest mouse is the smallest rodent in Europe and Asia, with adults weighing as little as a 2p coin they can run up and down blades of grass. Being so small has its challenges to researchers, we know surprisingly little about the natural history, status, and distribution of harvest mice in the UK, as they are elusive and hard to find.

Secondly, they are getting rarer. Their populations seem to be declining, with evidence suggesting a decline of 70% since the 1970s, likely due to changing and intensifying farming practices. But the good news is harvest mice are listed as Priority Species by the Cambridgeshire and Peterborough Biodiversity Group, and work is being done to conserve them across the country.

This harvest mouse is a part of a captive breeding program to reintroduce harvest mice into the wild, to be released in summer 2020. Image credit: Esme Ashe-Jepson

If you do get the rare pleasure of seeing a live harvest mouse, you might notice something strange about its inconspicuous tail. Though it looks like the tail of a normal mouse, they are the only mammal in the UK with a prehensile tail which they use like a fifth limb, similarly to a monkey, to grip grass and twigs as they scurry and climb, looking for seeds, berries, and insects. They are astonishingly fast, you may only catch a glimpse of red-gold and round black eyes before they disappear into the jungle-like long grass.

A 6 month old female harvest mouse, you can see their characteristic red-gold colouring, small hairy ears, blunt nose, and prehensile tail wrapping around a twig for support. Image credit: Esme Ashe-Jepson

With the Museum’s specimen you can get up close, an opportunity not many of us have to see these amazing creatures in such detail, and see their tiny feet and digits that they grasp with, being able to grip with just the back legs and tail means they can use their hands for other things.

Harvest mice are also master builders, and construct spherical nests out of grass, about the size of a tennis ball, suspended 50-100cm above the ground. No other mammal in the UK builds nests like these, if you are lucky enough to see a nest you have found evidence harvest mice are nearby!

Next time you’re walking past a grassland, meadow or reedbed, remember that what may look like a messy overgrown field of weeds to us is a haven for these tiny acrobats, which are an intrinsic part of our landscape.