The roost consists at its peak in excess of 1500 bats, being a maternity roost. It has been monitored for several years now and numbers have been growing year on year. The main concern was that the space they use to roost would be to small for much more expansion, however several licenced members gained access into the roost over winter and it would seem that there is still plenty of space for growth yet.
The above clip is a snap shot of the dawn swarming process, which can last for up to and beyond an hour, this is were lots of bats fly around the entrances to their roosts (swarm) before entering the roost for the day. There are two types of swarming the dawn as above and autumn swarming which is quite different.
Autumn swarming is a prolonged process happening over several hours and late into the night, involving far fewer bats. It occurs at hibernation sites, and several thoeries have been suggested as to why bats do this.
One of these is that the mothers are showing that years young the hibernation sites, another is that its has something to do with mating ensuring that genetic diversity is maintained in a population. Most bat groups are now undertaking work at autumn swarming sites to learn more about this behaviour.
Martin
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