Stop press people – big news! We have Horseshoe bats on the detectors! This is extremely exciting as it is the species that I set out to survey so their presence is, if not entirely unexpected, it is somewhat of a relief. The exact locations of their maternity and hibernation roosts is something of a closely guarded secret – to protect them against disturbance. But thankfully, when they are out foraging it can be relatively straight forward to get them on a detector – if you live in Devon that is. This is the Greater Horseshoe – the biggest bat you are likely to see in the UK (outside of a zoo). It is found all across Europe and is relatively common on a global scale, but here in the UK it has a very restricted range – covering the south-western corner of the UK up as far as South Wales and across as far as Hampshire-ish. Naturally the bats do not respect administrative boundaries so it’s something of a wobbly patch but you get the general idea.
They roost upside down – in classic bat style, hanging from the ceiling like little bat baubles. Their thin skin wings fold around their bodies hiding their fur – unlike crevice dwelling bats where the fur is visible and, if ID-ing, can be a useful guide.
Greater Horseshoes are not the first bats to emerge in the evening. If you can still see and are debating whether or not it qualifies as ‘dusk’ any bats you see are probably pipistrelles – the least picky of the bats. The ‘pips’ do not need old buildings, crumbling cool mines or ancient tree cavities to roost, they can cope fine with modern architecture (providing they can find a way in). The house on the other side of the close from us has bats in the roof. These are most definitely pips and they may well be the ones I say flying around outside my house in a previous blog post.
As I mentioned (here in my blog post) the visual representation of bat calls using the AnaBat detectors and AnalookW software helps you to ID the bats as they tend to have fairly distinct shaped calls. This graphic is of the horseshoe that my detector picked up over the weekend. With a flat, long call and static frequency there is only one other bat that makes a call like this – the Lesser Horseshoe Bat. Thankfully, it does so at a different frequency (around 110kHz). The shape of the bat call tells us something about the bat and how it navigates (remembering that these vocalisations are for echolocation). The constant call at a static frequency matches the larger, heavier, slower body of the horseshoe – they need a picture of the environment at a coarse scale if you like. The smaller bats call at a range of frequencies and break up their calls into smaller segments as they navigate more cluttered environments – information at a finer scale.
The Greater Horseshoe Bat populations in the UK have been recovering in recent years, though this has not always been the case and it is thought that the Europe wide population is as low as 1% of the population in the 1950s. This is largely due to increased intensification of agriculture (or whatever euphemism you prefer), resulting in fewer insects as prey, habitat for roosting and barriers to migration. This bat, like all UK bats, is a protected species in the UK, you need a licence to handle, disturb or manage bats – this is for their protection and it is important that those who are in a position to support the local bat populations do. That’s why I am so pleased to be surveying with three local farmers who love and appreciate their bat tenants. And just in case you were wondering, my detectors are passive and do not disturb the bats so I am not harming them by recording their voices.