7th February 2024

In this interview, BCT’s Research Manager Dr Lia Gilmour explains the links between the science of sound and bat conservation. We also talk about how she became a bat scientist and what it's like working at BCT.

Part 1 of this interview covers BCT’s AI-powered acoustic survey tool, which Lia's team is developing. Read AI and audio-identification of bats: Lia Gilmour interview part 1.

Last time we spoke about AI powered audio-identification of bats. Which bat species will AI be especially useful for?

For some species AI will significantly improve monitoring. For example, some traditional surveys are not great for species like common and soprano pipistrelles that engage in roost switching.

Manual roost counts provide a lot of our data and are brilliant for some species.

But species that roost switch move too much to get an accurate trend. You could turn up at a roost one year and count a hundred bats, but next year you turn up to half the amount, having upped sticks to neighbouring ‘satellite roosts’!

Bats, sound and science: Lia Gilmour interview part 2

Lia Gilmour is BCT's Head of Research and oversees our scientific work including our ground-breaking audio-identification system. This photo was taken during fieldwork in India.

And pipistrelles are an important species to monitor

Yes, although people celebrate the fact common pipistrelles can live in urban habitats – it's not clear that is a positive thing.

Overall, the trend is good, but regionally it could be a different story. So we need detailed, regional information to understand how those species fare in future.

And information about pipistrelles will help us understand change in a different way than a specialist bat. A bat species which lives in ancient woodland, for example, can give us an idea of how ancient woodlands are doing. Whereas generalist species like common pipistrelles can tell us about human environments such as urban or agricultural habitats.

There’s a long history of studying sound in relation to bats isn’t there?

Yes, lots of fields in biology study sound. For example, we have bioacoustics which is the study of biological sound. And there’s ecoacoustics - the study of natural soundscapes.

Specifically with bats, they’ve been studied for some time, because they perform active listening in such an interesting way. They send out an echolocation signal and the returning echoes are interpreted to navigate and orientate in space. With bats, there's a lot you can delve into in terms of say foraging calls or flight dynamics.

Excitingly, developments in automated sound identification technology now mean we have access to more information about biological sounds than ever before.

How does all this help bat conservation?

Traditional bioacoustics answers behavioural questions about bats, like how bats interact with predators, prey or their environment and how they are distributed in space.

But bats are threatened by a variety of things. Climate change, persecution by humans and habitat loss to name a few. And though currently all bats are protected in the UK, conservationists are worried that changes to legislation are coming.

So, what's important now is to understand how bat populations are faring and how that might be impacted by global change. And this new wave of audio-identification which I work on at the BCT will help us understand these things.

Bats, sound and science: Lia Gilmour interview part 2

BatDetect2 - the heart of the BCT's SCS which Lia talks about in part 1 of this interview - in action classifying serotine and common pipistrelle bat calls. BatDetect2 ref: Mac Aodha et al. 2022

Bats do incredible things with sound, don't they?

Particularly fascinating is how bats can change the way that they use their echolocation signals depending on the environment – they are hugely adaptable. A well-known example is the horeshoe bats and their use of Doppler shift compensation.

Doppler shift happens because sound waves reach your ear at different frequencies depending on your location in relation to the noise. A well-known example of Doppler shift is when you hear the higher pitch of a siren on a fire-engine as it approaches you, with the pitch becoming lower as it moves away.

Horsehoe bats call at a constant frequency but they fly pretty fast. So, their call echoes are affected by the Doppler shift, with the soundwaves squeezed to a higher pitch. Amazingly, they can dynamically lower their calls so that the echo always comes back to their ear at the same frequency. As humans we hear a crazy mix of frequencies, sounding like a warbling wail on a tuned bat detector. But bats hear just one frequency that their ears are tuned to receive.

NOTE: You can find out more about greater horsehoe bat and the lesser horsehoe bat on our species webpages.

Bats also communicate with each other

With some bats you get interesting communication about, for example, territory or defence of food resources.

For example, pipistrelles alter their social calls based on the amount of foraging resource available. When there are less insects, they social call more, to warn members of their species off, to keep more food for themselves. This has no effect on similar species, the social calls are species- specific.

We also know that males of some species sit in highly prized roosts and call to advertise their suitability to passing females.

Mothers and pups communicate too, don’t they?

We get ‘motherese’ in some bat species.

Motherese is a beautiful communication between mother and pups. The baby bats babble and learn from the mother’s responsive calls, just like humans do. And there’s also call-and-response between mother and pup to locate each other in a roost of thousands of bats of some species.

Your first chance to learn about bats was at university, where you studied biology with Gareth Jones. What caught your interest about bats?

Bats, sound and science: Lia Gilmour interview part 2

Lia's first encounter with a bat was when the family cat caught one (we don't know if this is the guilty cat).

I found the interaction between being a flying mammal and the sensory biology underpinning orientation fascinating.

But the clincher was a visit to a greater horseshoe bat roost.

Learning about bats was one thing, but being immersed was something else. What sticks in my mind is lying down under a tree line at dusk, watching as bats emerged and flew over us.

I was hooked.

When did you first work with the BCT?

I did a Masters before my PhD with Gareth Jones and Kate Barlow (who was then the equivalent of Head of Science and Monitoring) at BCT.

I learned about the amazing infrastructure that sits around bat work, like the volunteers and bat groups. Bedfordshire Bat Group helped with my field work on the Bechstein's bat - which you can only identify to species by holding in the hand. So lots of bat catching!

Was it hard to choose between traditional academia and a research department within a charity?

Kate Barlow was a huge inspiration for me, I loved the idea of working for BCT, but it seemed an elusive career path.

Of course, academia is hard too, and for women specifically. You get those ridiculous statistics where it's equal men and women at undergrad level, but as you get higher up you get less and less women in senior roles.

But I kept BCT in my sights.

And when I came off maternity leave, I saw Kate's old job advertised. I always wanted to be her, do what she did. But I was sure I wouldn’t get it! I did of course and did a year covering that role before becoming Research Manager.

Joining the BCT was a steep learning curve, but brilliant: to be able to put my academic knowledge to use in a different environment.

At BCT all the top science roles are held by women

Bats, sound and science: Lia Gilmour interview part 2

Lia during her PhD which was on evaluating bat deterrence methods and the development of a thermal bat tracking system.

It is a testament to what an amazing place BCT is to work. Of course, it’s also challenging, completely different from academia. There's a less time to do anything, you must think on your feet and manage your time.

But what comes with BCT is passion and inclusivity. Everybody's excited to be working towards the same aim and people who are marginalised are supported. BCT allows different people to thrive and progress their careers, whereas other environments, including academia, don't necessarily.

BCT ‘walks the walk’ in terms of good practise and it makes a massive difference, I feel very lucky to be part of it!