Inspecting the bat boxes

Bats, flying rodents eh? Tangle in your hair? Squeak a bit? Suck your blood? If you believe the common misconceptions about bats, you may think that they are either something to fear or a bit rubbish at being a mouse.That we know little about the true nature of bats probably doesn’t go a long way to fostering a massive change in their public image. However, there are people out there that think bats are pretty awesome and yours truly is one of them. [their scientific group name is Chiroptera, which means ‘hand wing’ – you then have the small bats, like we have in the UK, so, Microchiroptera and then you have the large bats Macrochiroptera, like the Asian and Oceanian fruit bats]

Grrr! Notice the mushroom shaped tragus inside the ear, a classic noctule feature!

Although for the day job (but at night, obviously!), I lead bat walks for the public as part of my wider duties in nature conservation and I do voluntary bat surveys for the Bat Conservation Trust, my close-up experience with bats is limited to some dead ones I’ve found and those in zoos.That it is illegal for people without a special licence to disturb a bat or its roost, let alone handle one, doesn’t really help people get face-to-face with these little winged marvels either.

Noctule looking very cute!

So, when the opportunity arose to help do some roost box inspections across the border in the badlands of South Croydon at the weekend, I (and a goodly number of other like minded folk) went along to offer our assistance. As we had a licensed bat worker with us, we were able to check the roosts legally.We had 99 boxes to rummage through around the woodland of Addington Hills. All the boxes were on Scot’s pine trees, generally in clusters of 12, with a mixture of wooden boxes and woodcrete boxes. Woodcrete is a mixture of wood and concrete (hence the name!) and is very hard wearing, with good thermal and humidity properties.
We first encountered bats in the second cluster of boxes, a small roost of noctule bats. Noctules Nyctalus noctulaare just about the biggest bat in the UK and are often one of the first bats to emerge, hence their moniker of the ‘early bat’. All of the bats were weighed, as well as sexed as best as could be and checked for their general condition. The noctules weighed in at the low to mid twenties (grams) and had all lost condition over winter, as they lose about 1/3 of their body weight or more as they hibernate over winter. However, they were all doing pretty well, even one with a large hole in his wing (the patagium)!

A brown long-eared looking a bit sleepy!

Next up were some brown long-eared bats Plecotus auritus. These are much smaller than noctules and only weighed around 6 to 7 grams, 5 to 6 grams less than their autumn weigh. However, again, all bats were in good nick with very few ectoparasites (ticks etc.). The ear length in long-eared bats is almost the same as their body but when not out hunting, they ‘uninflate’ their ears so that the surface area is reduced, keeping them out of the way in the roost but also reducing heat loss. The ‘ear’ you can see in the photo at the front is the tragus.

Sleepy noctules getting a rude awakening. Sorry guys!

On the last cluster, we got a final brown long-eared and a roost of 11 noctules in one woodcrete box. That I found and photographed this little group of cuties certainly made my day! See the rest of my photos from the day here.If you fancy finding out more about bats, I’m running a number of walks over the summer in Sutton (see the Events page for details!) but if you can’t make them, check out the Bat Conservation Trust for any walks or talk near you in the UK…
London Borough of Sutton Biodiversity Officer

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