Biodiversity Watch at Eddington: Bats

Project Ecologist, Mike Dean focuses this blog on bats with information about what’s been spotted at Eddington as well as guidance for if you spot any.

Some of you may have been lucky enough to spot some of Eddington’s nocturnal wildlife over the summer months, such as badgers, hedgehogs, owls and bats. Warm evenings between May and September are a particularly good time to look for bats, as they hunt for their insect prey along hedgerows, woodland edges, over grassland and even over the lagoon. They’re less likely to be seen within and around the buildings in the centre of Eddington.

If you want to spot bats it is really useful to have a bat detector, as this makes their echolocation calls audible. In recent years we have set up bat detectors in some of the more established habitats at Eddington. These automatically record each bat that flies past and the results have allowed us to identify the species present based on their different calls, although some species have very similar calls making it difficult to be certain in all cases.

Our surveys have told us that Eddington is used by at least nine of the 12 different species that occur in Cambridgeshire, and possibly more. Some of these roost in buildings, trees or bat boxes within the site. Some of the non-residential buildings have been specifically designed to try to encourage bat roosting. Other species may roost off-site, using the various habitats at Eddington to forage for insects.

Brown long-eared bats, for example, roost in some of the older farm buildings and common pipistrelles have been found roosting in several of the 50 bat boxes that have been installed in the site’s woodlands since the project started. Pipistrelles are smaller than you’d think – they weigh the same as a 20p piece – and yet they can eat an incredible 3,000 insects in one night.

Noctules are the largest species of bat that occur in the UK, although they are still smaller than the palm of your hand. They are known to roost nearby and can be very easy to see flying across Eddington at dusk, particularly on a clear night – they often leave their roosts while it is still relatively light. They also echolocate at a frequency that is much lower than other bat species, and actually audible to some people. In 2021 we recorded a lot of noctule bat activity in the southern part of Eddington, particularly around dawn and dusk, making us think that there might now be a roost within the site itself.

The nine different species of bat recorded in 2021 was also a significant improvement on the five species recorded when we last surveyed, in 2018. This suggests that there is an increasing diversity of habitats that are used by bats for foraging as the landscape planting has matured and the new and retained habitats are managed more sympathetically. The patches of woodland are now well connected by tall hedgerows, and there are areas of grassland and wetland habitat that also provide good foraging opportunities that were not available in the open farmland previously present at the site.

Here is the list of species recorded so far. Please do let us know if you think you’ve recorded any others.

Common pipistrelle
Soprano pipistrelle
Nathusius’ pipistrelle
Noctule
Serotine
Barbastelle
Brown long-eared bat
Daubenton’s bat
An unidentified bat of the genus Myotis, considered likely to be whiskered bat.

Please also remember the following:

In the extremely unlikely event that you find a bat, rather than simply see one flying, please avoid handling it unless absolutely necessary (and if you do have to, you must wear gloves as there is a low risk of rabies). Contact the Cambridgeshire Bat Group or the Bat Conservation Trust’s national helpline.
Bats are a protected species. It is an offence to (amongst other things) damage, destroy or obstruct a bat roost, or to disturb bats. Please don’t block their access points, tamper with bat boxes, or enter buildings where you know bats are roosting.

Read the other blogs in the series here.