Wednesday, 6 July 2016

Horseshoe Bats...

The two species of Horseshoe bats found in the UK are both very scarce. Like all of our bats they are offered the very highest levels of protection but they have still declined badly over the the years due to habitat loss and use of pesticides, which kill their prey. Luckily for us the west country is a stronghold for both the Lesser Rhinolophus hipposideros and Greater Horseshoe Rhinolophus ferrumequinum so the chances of detecting one on a bat monitoring session are greatly increased if you know where they hang out (no pun intended). And that's just as well as they have some of the quietest calls of any of the UK species being barely detectable from more than a few meters away. The echo location calls are radically different from our other bats in that they have a relatively long constant frequency (cf) note which is emitted through the nose assembly to pick up insects on or close to the vegetation around which they hunt. Their unusual facial features, that give them their name, are used to help focus the calls. Their flight is comparatively slower too and they can be observed hovering to pick insects off of leaves and branches or flying low through vegetation.

Last weekend a visit to a well know site in Devon paid off with a number of species found, although all appeared to be single animals en route to their feeding grounds. Click on the name in the captions below to hear a short audio file of the echo location call.

Lesser Horseshoe Bat Rhinolophus hipposideros
Note the mostly flat CF call around 112 Khz
The note around 56 Khz is the harmonic note.
Greater Horseshoe Bat Rhinolophus ferrumequinum
Similar in shape to the Lesser Horshoe but
emitted around 84 Khz and longer in duration.
In addition to the two target species we also connected with Common Pipistrelle, Soprano Pipistrelle, a single Leisler's Bat and a single Natterer's. Not bad for an hour's work!

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