NATURE NOTES: When is a pipistrelle not a pipistrelle?
It's amazing how things gradually change. It's not that long ago when, if you said you'd seen a pipistrelle bat, you meant that you'd seen a pipistrelle bat - Pipistrellus pipistrellus.
Now when you say you've seen a pipistrelle you have to say which as we now have three species to chose from! There are common pipistrelles, soprano pipistrelles (no not the large New Jersey version that's related to the Mafia) and nathusius' pipistrelle.
The common and soprano pipistrelles are the commonest and most widespread of all British bat species while the nathusius' pipistrelle, is much rarer and, to be honest, it's still a bit of a mystery bat as not much is known about it.
Scientists have only fairly recently recognised the soprano pipistrelle as a separate species to the common pipistrelle. It can only be reliably told apart from the common pipistrelle by its echolocation call which is on 55 kHz rather than 45kHz, this gives it its other name the '55 Pip'.
The nathusius' pipistrelle echolocates at around 39kHz. On a bat detector a series of clicks turns into "wetter" slaps towards the bottom of the frequency range. However, the pipistrelles' 'social' call is emitted at between 20 and 30kHz and is heard as a 'chonk', audible by some adults and children.
Pipistrelles are the bats that you are most likely to see zipping about at dusk around here. They appear fast and jerky in flight as they dodge about chasing small insects, which they catch and eat in flight. A single pipistrelle may catch and eat around three thousand flying insects every night!
Buildings are the favourite summer roost sites and contrary to popular belief that bats only live in castles, ruined buildings and belfrys, more than half of known roosts are in buildings less than 30 years old.
Pipistrelles like to roost in very confined spaces around the outside of the buildings, typical sites being behind hanging tiles, weather boarding, soffit and barge or eaves boarding, between roofing felt and roof tiles or in cavity walls. Pipistrelles rarely enter roof spaces except in the more stable, well-established large colonies found particularly in older buildings.
If you know what you're looking for you may notice a slight smudge around a well-used access hole, otherwise the only evidence of bats is the presence of droppings beneath the favoured entrance, on windows, window-sills and walls.
Pipistrelles can also be found roosting in tree holes and crevices, behind ivy and in bat boxes. The access hole can be a slit as little as half an inch wide (13mm). They can be active within the roost during the day, especially if young are present and the roost gets very hot.
They may also get very noisy as the time for them to come out draws near. They usually start to emerge from the roost about 20 minutes after sunset.
Large numbers of pipistrelles circling around the roost entrance at dawn make a fabulous sight!
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Weather for Wigan
Thursday 09 February 2012
Today
Light sleet
Temperature: 1 C to 2 C
Wind Speed: 6 mph
Wind direction: South
Tomorrow
Light sleet
Temperature: -2 C to 2 C
Wind Speed: 14 mph
Wind direction: South east
