You’re Britain’s smallest rodent, and even the pheasants are out to get you.

Your only means of defence are standing still or dropping from a great height, and cold weather and homelessness are also major killers. Damn right you’re going to spend your life weaving warm nests and popping out babies to put in them.

Too bad about the population crashes though.

But it’s not all bad news being a harvest mouse.

For a start, it has a pretty golden coat and large eyes and ears, placing it a few notches higher on the “cuteness” scale than its house-dwelling cousin. It’s also the only British mammal with a prehensile tail for gripping on to grass stalks, and the five teeny digits on each foot are practically opposable, making it an expert in its field (see what I did there).

Photo by Greg Newman.

While it’s not exactly welcomed in grain storage over winter, it’s still a “BAP” or “Biodiversity Action Plan” species in the UK, so it’s protected throughout the country and has even been reintroduced in some areas. Perhaps a bit later than expected, but I’ll come back to that.

Thanks to its fired up metabolism and tiny size, one of its favourite hobbies is sleeping.

Day and night, the harvest mouse lives on a rolling three-hour schedule. Every third hour of sleep, up it gets for half an hour of chomping either seeds, or in summer, garden pests. It leaves a sickle-shaped calling card in cereal grains, and is careful not to waste the other thing it leaves behind.

Essentially, its first plop is just a practice run. Cellulose can be a pain for it to digest, so it has a large cecum, or pouch in its abdomen, to help break it down. Unfortunately by the time the job’s done, the broken down cellulose is too low in its gut to be reabsorbed, so the harvest mouse, er, does a bit of recycling, so its stomach and higher gut get all the goodness next time around.

After munching, it goes back to snoozing in safety.

Photo by Chris Salt.

This can either be a burrow in the soil, or more likely, a woven nest ball about 1 metre (3.2 feet) off the ground. However, if it’s a singleton, its construction methods can leave a lot to be desired.

The real craftsmanship is borne out of love. Well, the aftershock of hormones, at least.

Harvest mice parents will weave a nest ball of 6-13 cm (2.3-5 inches) diameter from three layers of grass, and floof out a comfy shredded bed inside for the incoming kids. There may be more than one entrance, but regardless, once it’s finished, Mum will seal all of them up and leave Dad outside. Forever. [Insert 1980s divorce joke here.]

After 3 weeks Mum will pop out her litter of 5 or 6 young, and within 3 days, despite still being blind, they’re able to hang on to a grass stalk. They then leave the nest at the age of 35. Days.

As for Mum and Dad, there don’t seem to be any hard feelings, because as little as two weeks after the kids have been born, they’ll be at it again, although probably not with each other. When you have a lifespan of 18 months tops and only breed from May to September, you might want to play the field a bit (fnar). And each brood will have a shiny new nest for Dad to be shut out of again.

Alternatively, if you fancy having harvest mice in your garden, they’d be equally cool with a tennis ball on a stick with a hole in it.

It’s thought that, thanks to modern farming practices like pesticide use, the harvest mouse has had a bit of a hard time finding a home. Reedbeds, roadsides and cornfields are all the rage, but of course have their own risks.

As well as being a pain to draw.

Even without these complications, another type of bad luck comes for it in threes – every three years, it seems to suffer an unknown population crash, and then builds itself back up over the next two. That’s not including the general decline in harvest mice throughout the country.

It’s incredibly rare north of the River Tyne too, and so in 2004, PhD student Wendy Fail tried her luck at reintroducing it to Northumberland.

To help them acclimatise, and protect them from yet another enemy – wood mice – the 240 captive bred harvest mice were released in small cages at first, and then gradually into a coastal area. Typically, when a subsequent population survey was carried out, they appeared precisely zero times in any of the (humane, non-lethal) traps that were set up, and the project was deemed a failure.

Until 15 years later.

At least two harvest mouse nests were discovered in 2019 in the East Chevington Nature Reserve, the area where the original group was released.

If the harvest mouse knows how to do anything, it’s lie low before popping out of somewhere. And, for most people, in as cute a way as possible.


Latin: Micromys minutus

What? Teeny tiny golden field mouse.

Where? Grassland, hedgerows and woodland in Europe and parts of Asia.

How big? 5-7 cm / 1.9-2.7 inches, with a tail of 6 cm / 2.3 inches.

Endangered? Least Concern due to a high population and wide range, but it’s at risk in certain areas with regular population crashes.

Probable motto: Here are three more things I like: food, sleep, and sex.

They look adorable. Do they need my help at all?

They’re thought to have declined in some areas, most likely due to farming practices like pesticide use, but we haven’t looked closely enough to be sure. Ways of helping other than plonking a tennis ball on a stick can be found at the People’s Trust for Endangered Species and the Wildlife Trusts.

Just to prove I’m not fibbing:

Barkham, Patrick. 2019. “Harvest mice found thriving 15 years after reintroduction efforts“. The Guardian.

Editors of Encyclopaedia Britannica. No date. “Harvest mouse“.

Harvest mouse“. No date. The Wildlife Trusts.

Harvest mouse“. 2008. The Guardian.

Ivaldi, Francesca. No date. “Micromys minutus“. Animal Diversity Web.

Kryštufek, B. et al. 2019. “Micromys minutus The IUCN Red List of Threatened Species” 2019: e.T13373A119151882.

Micromys minutus“. No date. Wildpro.

Species fact sheet: Harvest mouse“. No date. The Mammal Society.

Featured image credit: Photo by Chris Game.