Bats are important ecosystem indicator species, controlling populations of several insect species. As insect-eating mammals, the population of bats can reveal negative changes to the environment.  

With this in mind, I joined a few members of the Derbyshire Bat Group one Autumn evening at Derwent Meadows, to conduct a walking survey to record which bat species we came across.  

Derwent Meadows is a local wildlife site managed by the Derbyshire Wildlife Trust on behalf of Derby City Council and the Derby Commercial Park. It sits on a S-shaped bend in the River Derwent, surrounded by the warehouses of Derby Commercial Park, next to the Raynesway and, not too far away from the houses of Alvaston and Spondon. 

Seventeen species of bat live and breed in Britain, and Derbyshire is home to 13 of these. Previous surveys have revealed that Derwent Meadows is called home by up to seven of these Derbyshire species.  

All species of bats are protected, and their roosts are legally protected in the UK under both domestic and European legislation, making it illegal to harm or disturb them without a license. 

Bat population across Great Britain is relatively stable over the long-term, but short-term trends indicate that there may be external pressures facing bat populations. Local bat conservation groups are key to understanding, exactly, what these pressures may be. 

Several Derbyshire Bat Group members are trained and licenced to carry out regular surveys at several locations across Derbyshire. Some surveys involve installing and checking artificial bat boxes, creating and making space for these intriguing nocturnal mammals. Derbyshire Bat Group is one of several local groups keen to take action for nature by advancing the protection and conservation of the environments bats are found in within Derbyshire. 

Bat’s the way we do it: a guide to surveying 

Bats can be on the wing at any time from dusk until dawn and, being quick and agile hunters of all sorts of flying insects, they are only usually glimpsed as swift shadows against the darkening (or brightening) sky.  

Bats navigate and hunt using echo-location. They send out high frequency sounds from their mouth, or nose, which bounce off objects and are picked up by the bat’s ears. This allows bats to build an accurate picture of their surroundings and focus on their prey, even in complete darkness. 

Most calls from bats are beyond the range of sounds most humans can hear, so to find the bats, we were equipped with bat detectors. These are small hand-held devices, about the size of a mobile phone, which pick up the bat’s calls and make them into a sound humans can hear. 

Different bat species make sounds at a different range of frequencies, meaning that it is possible to identify which species you are hearing. However, there is some overlap in the frequency of calls species make and they make different sounds when they are hunting prey, or if they are talking to each other in what are called ‘social calls’. It takes the keen ear and expert knowledge of the Derbyshire Bat Group members to get a definitive answer.  

Taking tree-mendous care 

Recent tree surveys have revealed the need to carry out work on some of the large hybrid poplar trees at Derwent Meadows. These works are needed to prevent them being blown over by strong winds into the woodland and onto important public infrastructure.  

To carry out this work, we have had to survey the trees to find out if they are likely to contain any bat roosts and ensure we know where they are making themselves at home to try to minimise the disturbance to bats. If any work is required on a tree that may disturb bats, we must work with Natural England to ensure we have the appropriate permissions and licences in place before work on any trees starts. 

Using the results of these surveys, we will make evidence-led decisions about the type and extent of any work required, to minimise disturbance to bats, whilst maintaining the safety of any visitors to site. The works will also provide new natural homes for bats or new artificial homes, in the form of bat boxes, ensuring space is made for the bats and their food to continue thriving.   

The results?  

On the evening in question, we saw four of the seven species on site: Noctule bats, large bats which fly quite high; Common and Soprano Pipistrelle bats, two smaller bat species which we found flitting between the trees and Daubenton’s bats, a medium sized bat which hunts at low levels over rivers and ponds. 

We hope to be continuing the surveys and work with the Derbyshire Bat Group at Derwent Meadows into the future to ensure the creation of more nature-rich habitat for bats and other wildlife. By helping to monitor one of Derby’s local bat populations, we are working towards our vision of a Derbyshire where people and wildlife thrive together in both rural and urban areas. 

Learn more about urban rewilding here