Bat box checks!

Today’s blog post will be about a really cool thing I did a week ago! I was fortunate enough to meet the Berkshire and South Buckinghamshire bat group on the 3rd of August. They invited me along to a bat box check run by Hampshire bat group on the following day! This post is therefore going to be all about the why’s, where’s and how’s of bat box checks.

Bat boxes are artificial bat roosts that anyone can build and put up in their garden*. The RSPB have nifty instructions for how to make a simple one here:


* – One issue with bat boxes is that bats (in the UK at least) are very picky. It can take years for them to end up using a bat box, but having one up is still better than nothing! Plus it’s a fun DIY project!

Bat box checks are a super important way we can survey how many bats there are in an area. I must put a little warning here and say that in the UK, you can only conduct a bat box check if you have, or are working alongside someone who has, a specific license to do so. If not, it is illegal to intentionally disturb a bat roost and you can be fined and even face imprisonment1,2. Therefore DO NOT TRY CHECKING BAT BOXES AT HOME. Chances are, however, if you live in the UK, you can get in touch with your local bat group (which you can find through the BCT website: and see if you can tag along to any of the checks they run throughout the year. That is what I did!

Two common types of bat box

There are many types of bat box. The type I’ve most encountered is the Kent bat box where the bats lie snug between slats of wood. There are also Schwegler bat boxes (see pic) which are quite expensive but important for bat box surveys as they let you catch and measure bats. Many bat enthusiasts also design and build their own bat boxes. I’ve seen some marvellous creations, the most notable was one containing polystyrene insulation to keep the bats warm in winter! Each box has a specific way it is checked for bats. Kent bat boxes are simple – you can shine a torch* up inside from below, or poke an endoscope inside. Schwegler boxes are opened from tree height and if bats are present, the batworker will bring the box down to assess the bat’s condition.


* – briefly of course, you don’t want to spook any snoozing bats!

Bat boxes are more often filled with moths than bats – it’s a wonder they don’t use them as restaurants!

Box checks are carried out in the day time, as that’s when the bats are using the boxes to snooze in. Myself and members of the two bat groups spent the morning surveying an area of woodland. It was super nice for me to be invited along, as living in the middle of a large town means I don’t often get to be surrounded by trees! We worked together to check many different boxes. More often than not, the bat boxes would contain a whole host of other animals. The most humorous inhabitants were clusters of moths! I’d have thought a bat box full of moths (the favourite food of most UK bat species) would be the bat equivalent of a gourmet restaurant! But no, occupied boxes were few and far between.

We weren’t let down, though, as we found our first bat snoozing in a Kent box! Having seen the majority of roosting bats in Honduras and Costa Rica, I am always taken by just how small UK species are. So often I hear people telling me about finding baby bats, but when I ask how big the bat they found was, I enjoy telling them that what they’d usually found was a full grown adult! We continued our search and this time, found an occupied Schwegler box. For this box, the licensed ecologist removed it from the tree and gently took the snoozing bat out to measure it. I was totally honoured when they asked if I’d like to help with this*!!!


* – Now I must mention that I was only able to do this because I’ve had quite a bit of experience handling and measuring bats in Honduras. I also have an up-to-date rabies vaccination and am working towards having a licence one day.

The anatomy of a soprano pipistrelle in the hand (very scientific!)

Given that bats are (pretty much) my entire world, you can imagine just how excited I was to be able to hold one! The bat in question was a male soprano pipistrelle (Pipistrellus pygmaeus). These bats are just awesome! They’ve only recently been recognised as a separate species to the common pipistrelle, and are named after their higher pitched echolocation calls – which is adorable! Soprano pips have paler faces to their common pip cousins, and also have differing wing patterns and a small bump on their nose between their nostrils3. I’ve been told by bat carers that soprano pipistrelles tend to be among the grumpiest, noisiest and smelliest bats to care for*! The bat we found in the box was also possibly at his stinkiest point of the year. It’s now breeding season for bats in the UK, and so he’d be busy secreting all kinds of sexy smells to attract the ladies. To humans, this smells like a sort of musty, nutty, slightly urine-like odour, but to female bats, I’d imagine it’s quite pleasant!


* – This fact was my saving grace when I found myself conducting a bat walk, a few months back, for two very young, hyperactive children who weren’t that interested. I managed to get them excited when I mentioned we were trying to spot the ‘stinky bats’!

We only took a few measurements before putting him back in his Schwegler box and placing it safely back on the tree. We checked his weight, forearm length and finally his reproductive status. Male bats definitely invest heavily in their genitals around this time of year! Despite being tiny, his testicles were about 1/6th of the size of his body*! A few more boxes later and we were able to find a harem of female soprano pipistrelles. These girls will also be on the look out for mates now they have finished nursing their pups. Checking the female bats nipples allowed us to check if they had had a pup this year. If you are of a non-biology persuasion, this might seem quite strange! But I assure you, this information is super important for telling us about how well the bats are reproducing, and therefore how the population of this species is doing.


* – That’s me just estimating, don’t quote me on that!

In total, we found 9 soprano pipistrelles that day. It was absolutely fantastic to see them all, and also observe the scientific processes. Bat box checks in the same area aren’t carried out very often to ensure that the bats aren’t too disturbed. None of these checks are carried out in the winter as hibernating bats must be left alone to prevent them waking and burning precious calories. This time of the year, however, is a great time to contact your local bat group and see if you can tag along. It is always amazing to see a bat up close, and learn all about the science happening where you live! The records collected from these checks will usually be sent to national databases around the country, allowing us to see trends over time and trends in different areas. Pretty awesome stuff!

To finish, I’d just like to say a massive thank you to the Berkshire & South Buckinghamshire Bat Group and the Hampshire Bat Group for inviting me along! Keep up all the great work!


  1. Wildlife and Countryside Act (1981)
  2. Conservation of Habitats and Species Regulations (2017)
  3. Dietz & Kiefer, 2016 | ISBN: 978-1-4729-2202-1

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