As the end of the year draws closer, my mind has cast back to another story about bats… Well it’s not just that I’m obsessed with bats, but I do like sharing good news – in autumn we found that we have two species of bats newly visiting the wildlife garden.
During the week of our Bat Festival and International Bat Night, and through the help of Philip Briggs of the Bat Conservation Trust and tree surgeons Liam and James from Wassells Arboriculture, an Anabat recorder was installed in the lime tree overlooking the pond. This provided us with a new way to register bats visiting our small patch of London.
Recording of bats began here twenty years ago, when the garden first opened, through John Tovey of the London Bat Group. Up until last year the usual methodology was to spend several night hours with our hand-held bat detectors from dusk onwards, and occasionally around dawn.
Via this method we have often seen bats and picked up the echolocations of common and soprano pipistrelles; we were fortunate to hear and see common pipistrelles on the night of our Nocturnal Wonders – Moths and Bats evening that we held for our Museum Members on 27 August. However, on another evening we can easily miss out.
With the Anabat, we were able to form a good picture of bat activity over the period of a month, but without having to stay up all night. Philip Briggs describes how the Anabat works:
The Anabat is a type of bat detector designed for passive surveillance of bats. It is programmed to operate each night between dusk and dawn during which period it triggers a recording each time an ultrasonic sound is detected.
The recordings are then uploaded to a computer and analysed using sound analysis software in order to identify which bat species’ calls were recorded. Each recorded file contains information on the date and time at which the recording was made, enabling information to be collected on seasonal and nightly patterns of activity for each species.
Following the recording period, Liam returned and removed the Anabat and Philip Briggs analysed the sound data. This showed that the species foraging in our garden are not only common pipistrelle (Pipistrellus pipistrellus) and soprano pipistrelle (Pipistrellus pygmaus), but it confirmed that Nathusius’ pipistrelle (Pipistrellus nathusii) were also foraging.
We had suspected that they might be visiting us and now we had proof. And a new visitor, a Leisler’s bat (Nyctalus leisleri), was also found to be coming through the garden for a quick recce.
Although Nathusius’ pipistrelle is still a rare bat in this country, it has been recorded increasingly around London, including just up the road in Kensington Gardens and now it has put our own garden on its map – this is obviously a good place for bats to dine out.
As with soprano and common pipistrelles, Nathusius’ pipistrelles include aquatic flies, midges, mosquitoes and caddis flies in their diet which are plentiful in the Museum’s pond.
Leisler’s bat is a woodland species normally using old trees for roosting, but it also uses buildings. Leisler’s feed on moths and beetles as well as flies and caddis flies. London is something of a hot spot for the species and we’ll be setting up the Anabat again next year to see if one or more returns.
All four of these species use buildings and old trees to roost. We do not know if they roost here but we do know that they must be very close by because they appear here soon after dusk and before dawn. The Nathusius’ pipistrelles were heard around 5.00 am and – at that time in September – they wouldn’t be far from their ‘home’ roost.
It’s always exciting to find species new to the garden, and especially so with bats which are indicators of good habitat. As Philip says:
The results from this survey show that the garden is regularly used by at least three species of bat which provides further evidence that it is a valuable wildlife habitat in an otherwise very built up area.
And on that note we can end our year with some photos from sunnier times.
Happy new year when it comes and until the next time…