I am taking part in the "Pipistrelle Summer Colony Count 2002", which is part of the National Bat Monitoring Programme run by the Bat Conservation Trust (a band of enthusiasts) and the Joint Nature Conservation Committee (a government department). All I have to do is count the bats leaving the roost in my roof around sunset on two occasions, this week and next week, and make a note of the timing of emergence, weather and air temperature. This week's count revealed 97 bats, emerging in ones, twos and threes and flying out over the garden. I can hear them chattering noisily not only just before departure but, in hot weather especially, during the day. I know they are pipistrelles partly because they are our only native bat that lives in such large colonies in buildings (including churches but rarely in belfries). This has been confirmed when I have had to rescue bats that have taken a wrong turn and come into the house. The pipistrelle, which once went under the descriptive name of flittermouse, is our most abundant bat but there has been a serious decline over the past decade. These annual colony counts and an assessment of changes will become the cornerstone for the species' conservation. There is an interesting complication to these counts. It was discovered recently that the common pipistrelle (Pipistrellus pipistrellus) is, in fact, two species. People studying bats with "bat detectors" - gadgets that transpose their ultrasonic insect-locating sonar into audible tones - found that pipistrelles transmit at either 45 or 55 kHz. Evidence accumulated to suggest that there were two separate populations of bats and DNA analysis has confirmed these as two species. The new one - the 55 kHz bat - has been named Pipistrellus pygmaeus and is popularly called the soprano bat. Not much is known yet about the differences between the two species but it seems that the soprano pipistrelle may hunt mainly over water. I was tickled to find that my bats are sopranos: a brand-new species rather than the old mundane one. I ought to close with a joke about sopranos and die Fledermaus, but I can't think of one.
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