Tag Archives: woodmice

Dormouse activity in my site in 2016

I have been in partial hibernation this last couple of months, hence the lack of blog posts. But I have managed to do somethings, one of which is sift through my dormouse data from last year. I’ve made a little animation showing how dormice and other animals have used the boxes at my monitoring site over the last couple of years.


It’s great to see dormice making use of the boxes we put up in 2015. Hopefully it means this year they’ll start making use of the boxes we put up at the start of 2016.


Dormousing: November 2015

After the bumper crop of plump dormice in October, I was looking forward to seeing if they would still be around in November. My first attempt had to be abandoned at the last minute due to rain. Things didn’t look much better for my final opportunity of the month, as the rain started just as I left home. But we banked on it being dryer under the trees, and had a brolly to keep any dormice we found dry.

There were plenty of nests to check, so it took quite a while. We did find a couple of woodmice (only the second time this year we’ve found them at this site). But no dormice – they’re probably hibernating already, despite the mild autumn we’ve had so far.

As the dormousing year comes to an end, and the dusters get a good wash, it’s time to reflect on my first year with my own site. It was quiet for the first few months, but by the end there were nests in nearly every section of the site we have boxes in. This is very encouraging, and I hope to get another 11 boxes up in time for next season (bringing the site up to the standard 50 boxes). It’s sometimes been hard to get volunteers – I don’t know if that’s due to the location or just that everyone knows which sites have the most dormice.

I was quite nervous being in charge to start with, but seem to have got my confidence up now. I have really enjoyed watching the site change with the seasons, and look forward to getting to know it even better next year.

First dormouse at my new site

After last month’s disappointment (and the huge proportion of boxes that were being used by birds) I didn’t have high hopes for the dormouse box checks this month. But, once again, I was wrong. On my fourth monthly box check we finally found a dormouse!

Just the one, but a very cute one. It only weighed 12.5g, which is quite small for an adult. But weights tend to be low in June, as many won’t have been out of hibernation all that long.

It was the first dormouse I’ve seen this year, so I was quite relieved it was torpid and easy to handle. I think the warmth of my hand started to wake it up, as it clung to my fingers. But it seemed to go straight back to sleep when it was back in its nest, so will just have hazey memories of a weird dream.

Torpid dormouse found on my box check in June
Torpid dormouse found on my box check in June

I say its nest – in fact, he has just moved into a bird’s nest, so it’s not at all typical of a dormouse nest. Maybe, since it’s so small, it was preserving energy for feeding, and making do with a bird’s nest until it has put on a bit of weight. It’s not unusual for dormice to build a nest on top of a used bird’s nest, but this dormouse hasn’t got round to home improvements yet. All the bird’s nests in boxes were empty this month, so hopefully the dormice will start to recolonise them.

Dormice aren’t the only mice taking over from birds – one former bird’s nest had a couple of apodemus mice hunkering down. I didn’t manage to see their necks, so can’t tell if they were woodmice or yellow necked.

Seeing the dormouse made my day – they really are incredibly endearing. And hopefully it will be the first of many.

How to tell who’s been nibbling your nuts

Hazel nuts are popular with many small mammals (our native dormouse, muscardinus avellenarius, is called the hazel dormouse for a reason). And the way a nut is opened can tell you who’s eaten it. This is particularly handy for telling if dormice are present, as you’re very unlikely to see one.

So, starting with the easy one. It takes strong jaws and teeth to split a hazel nut. So if you find a discarded nut shell split in two, or shattered, the nut has probably been eaten by a squirrel.

Bank voles also have big, strong teeth, so can bite rather than nibble through to the kernel. Quite often they will leave an irregular, roundish hole in the shell. They tend not to leave lots of teeth marks on the shell near the hole, unlike mice.

Now we get to the tricky part: distinguishing between nuts eaten by apodemus mice (woodmice and yellow-necked mice) and dormice. Both sorts of mice nibble neat round holes in the shell, so you need to look closely. A hand lens or magnifying glass helps.

Hazel nut that has been nibbled by a woodmouse or yellow-necked mouse: note the toothmarks on the inner slope of the hole, and scratch marks around the outside of the hole
Hazel nut that has been nibbled by a woodmouse or yellow-necked mouse: note the toothmarks on the inner slope of the hole, and scratch marks around the outside of the hole

A hole nibbled by an apodemus mouse will have teeth marks going down the edge of the hole (vertically). They leave more scratches on the outside of the shell than bank voles. Hopefully you can see both those features in this picture.

Nut nibbled by a dormouse. Note the smooth inner surface of the hole, and the scratches outside the hole.
Nut nibbled by a dormouse. Note the smooth inner surface of the hole, and the scratches outside the hole.

The inner edge of a hole made by a dormouse will be much smoother, as they gnaw around the hole, rather than down. But they do leave lots of scratches around the outside of the hole.

Another clue to help you tell the difference between apodemus and dormouse nibbled nuts is where you find them. If you find a cache of nibbled nuts, it’s likely to be apodemus. Dormice generally tend to eat and then drop nuts where they find them, so their nuts are often more spread out.

If you find a nut with a really tiny hole (maybe 1-2mm across), this has probably been eaten by an insect.

Nut A: who's eaten it?
Nut A: who’s eaten it?
Nut B: who's eaten this one?
Nut B: who’s eaten this one?

Here are a couple more close-up photos of nibbled nuts. Can you tell what’s eaten them? I will put the answer in the comments to this post. Let me know how you get on.

I’m starting to put together a page of photos of mammal signs. This will develop as I delve into my archive, and take more photos. I hope this will eventually become a useful reference (particularly as many books have line drawings rather than photos of these sorts of things, which can be rather hard to interpret). I’ll let you know when it goes up.

Looking for harvest mice at an airport

6.10am on a chilly November morning. It will be almost another hour before the sun rises, and a mist clings to the ground in the pre-dawn gloom. Most sensible people are still in bed, but I’m at Gatwick Airport. Not catching a flight to somewhere warm, nor waiting to welcome a loved one home. I’m here to see some wildlife.

An airport seems an unlikely place to see any exciting animals. Acres of tarmac, deafening noise, light and air pollution. I was intrigued, which is partly what brought me there so early in the morning. That and the hope of seeing a harvest mouse.

Beyond the public areas of the airport there are some pockets rich in wildlife. They have Bechsteins bats, the rare long-horned bee and great crested newts. But it was harvest mice I was interested in.

Chilly morning at Gatwick airportThe previous night Jim Jones from Surrey Wildlife Trust and Rachel Bicker, an ecologist at Gatwick, had set out 60 small mammal traps, and we were here to see what had been caught.

Jim showed us how to check the traps, and if occupied, how to weigh and sex the animal, then reset the trap with fresh bait. Our first occupant was a male field vole. Jim clipped his fur (so we could tell if we catch him again) and released him into the long grass. Voles are quite laid back creatures compared to mice – their response to danger is to stay still in the hope of not being seen, which makes them relatively easy to handle. The woodmice we found in some of the other traps were a bit more challenging.

Jim the trap-happy field vole
Jim the trap-happy field vole

So, nothing more exciting than a field vole from the first check. Time to go home and try to warm up.

The traps need to be checked three times a day, so I still had a couple more opportunities to see a harvest mouse. I returned at lunchtime, and the whole scene had transformed. The mist had disappeared, and the sun warmed us as we worked. The vole we had caught and released that morning had found his way back into a trap. The next occupied box we found gave us a surprise. It felt like it was buzzing when I picked it up, and I expected a very angry mouse to bounce out, but it turned out to be a disgruntled wren, who flew off to safety. That was our lunchtime haul, but we were also treated to views of a kingfisher and a sparrowhawk.

wrenThe evening check felt very different again. The planes seemed bigger and closer in the dark, and we had to rely on torch light to see the traps. The same vole had found his way back into a trap. Having seen him three times in one day, we decided he needed a name, and settled on Jim. No wrens this time, but another woodmouse or two.

Sadly no harvest mice showed up for me. The traps stayed out the rest of the week. Rachel and a team of dedicated volunteers checked them three times a day, come rain or come shine. But no harvest mice turned up.

It was a worthwhile experience. I’ve seen a field vole and learnt how to distinguish it from a bank vole. I’ve learnt how to use three types of small mammal traps, and seen a kingfisher. And I’ve had a fascinating glimpse into the wildlife of Gatwick Airport. You can read more about biodiversity at the UK’s second busiest airport on the Biodiversity Gatwick blog.

Dormouse handling

I have been helping out on dormouse box checks for several years now, and for the last few years I have been working towards my license. Dormice are protected by law, and to disturb them in any way you need a license from Natural England. To get this you have to have been trained and have experience of handling dormice of all ages. This can take a while to accumulate if, like me, you mainly do sites with few dormice. Anyway, I now have the necessary experience, but needed to show one of my referees what I am like at handling dormice. I went on a check with him last month, but there were no dormice, so this month I had to try again.

The two sites I visited this month were ones I hadn’t done before. This added an element of treasure hunting / letterboxing / geocaching without gps to the process, trying to find inconspicuous wooden boxes in dense, tangled woodland. Just as well I like a challenge!

The first site was on the edge of a golf course. As well keeping out of the way of golf balls, we also had nettles as tall as my shoulders, brambles and dense, unforgiving blackthorn. The place wasn’t brimming with dormice, so it was a relief when Dave found one sitting on top of its nest in a box. We took the box off the tree, putting it into a large rubble sack. By the time we got the lid of the box off again, the dormouse had disappeared into its nest.

Cautiously I put my fingers into the cavity of the nest, to try to gently coax the mouse out. The nest was wonderfully warm, especially as it was quite a chilly morning, and the mouse was not keen to come out. I could feel some other warm, tiny bodies, and we realised there were young babies (pinkies who had not yet grown fur) with their mum. We didn’t want to disturb them anymore, so quickly and quietly put the box back on the tree and left them to it.

It was lovely finding a young family, but it did mean I still hadn’t had a chance to demonstrate my handling skills. We found no further dormice at that site, although I did come across a nest with three woodmice sitting on top.

So, I had to hope we would find some dormice at the next site. The chances were slim, as last month’s check had found none.

The second site started with some excitement, as the first box contained a pygmy shrew. These are tiny insectivores (smaller than the first joint of my thumb) with long, mobile, Womble-like noses. They have a very fast metabolism which means they need to eat more or less constantly.  It’s not the first time I have found them in dormice boxes. In fact, dormice boxes seem to attract a lot of wildlife, including mice, birds and insects. We often find moths, millipedes, slugs and other invertebrates in them, which is probably what attracts the pygmy shrews.

Most birds have finished nesting now, so dormice have less competition for boxes. Sometimes they build their nests on top of disused bird nests, and sometimes they just make use of the bird’s nest without much alteration. They seem to particularly like wrens’ nests, and who can blame them. Wrens fill the boxes up with moss, creating a large square cavity in the middle, not too dissimilar to a dormouse’s nest (although dormice tend to weave their nests out of strips of honeysuckle bark, leaves and other locally available materials). Wrens also keep their nests much cleaner than other birds (messy bluetits for example). So when I came across a wren’s nest with what looked like mouse droppings on top, I thought it was worth further exploration.

I was right. The nest contained a very lively male, who gave me a perfect opportunity to demonstrate my skills, catching him, sexing and weighing him, then returning him safely to his nest. It’s only my second dormouse of the year, so I was relieved to find I wasn’t too rusty. My referee was happy with how I did, so now I just need to fill in the paperwork!

British Animal Challenge: August update

I’ve been making the most of the summer this month, spending lots of time watching wildlife. I have been focusing on trying to see some new bat species, and a water shrew.

I have had mixed success with bats. A bat walk led to no new species, while an unaccompanied expedition in Devon found two new species, only one of which I could identify (soprano pipistrelle). A more recent bat walk was more successful, with three new species – more on that next week.

As for water shrews, I have spent quite a bit of time looking for them at a site I know they inhabit, but no luck so far. I think I may have heard one, but I haven’t seen one.

Apart from new species, I have also seen:

  • A hare
  • Common pipistrelles
  • Woodmice
  • A pygmy shrew
  • Rabbits
  • Hedgehog
  • Frog
  • Dormice

As for next month, I’m not going to have so much time for wildlife watching, as a work trip is taking me out of the country. But I do have a trip to the West Country planned, where I will try my luck with more bats and cetaceans.