Bats, sound and science: Lia Gilmour interview part 2

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.

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.

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.

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.

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.

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.

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.

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!

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.