ECR Spotlight – Michael Pedersen Free

Michael Pedersen

How did you become interested in biology?

I grew up in Southern Denmark near the Wadden Sea which is a UNESCO World Heritage site. One of my first memories of being fascinated by the biology was seeing the great starling migrations aptly nicknamed ‘Black Sun’, where thousands of birds collectively migrate and move amongst each other in mesmerizing displays. This inciting incident sparked my curiosity for the natural world. This curiosity was then nurtured both by the TV greats such as David Attenborough and the late Steve Irwin, but also by my university lecturers and supervisors who really brought to light the wonderful complexity and intricacies of the world which surrounds us.

Describe your scientific journey and your current research focus

I have a BSc, MSc and PhD in Biology from Aarhus University in Denmark. The formal beginning of my scientific journey was during my MSc project, where I wanted to investigate the contrasting claims of sound production costs in bottlenose dolphins. Theory suggested that their sound production should be very cheap, but empirical data suggested sound production costs were some 20–50% of resting metabolic rates. In my MSc, I found support for the initial theoretical values and managed to publish the results of my thesis as my first JEB paper (doi:10.1242/jeb.212498).

I then moved on to do a PhD in the same lab where I did my MSc, where I investigated the biosonar performance in echolocating bats under controlled laboratory conditions. During my PhD work, I looked at how bats accommodate acoustic interference emitted from a landing target which overlaps spectrally and temporally with their echolocation calls to varying degrees. Early on during my PhD, I managed to publish two additional papers in JEB: one as a co-author showing that bats are resilient to masking noise during a landing task even at very high noise levels (doi:10.1242/jeb.242957), and one as a first author calling the decades-old notion of ‘spectral jamming avoidance’ into question (doi:10.1242/jeb.243917), suggesting instead that bats employ much simpler behavioral strategies to accommodate acoustic interference via a bandwidth-dependent Lombard response.

In my most recent paper, which has just been published in JEB, we show that echolocating bats can successfully land when exposed to clutter (extraneous echoes from background objects) in their auditory scene. Interestingly, they do so without changing their biosonar source parameters, and without any apparent range ambiguity, which suggests that they can keep track of echo streams from several echo sources, and we propose they do so via auditory stream segregation.

I am now a postdoc based in the same lab where I did my MSc and PhD, and I have the pleasure to both work with respiratory physiology and echolocation in toothed whales and conduct behavioral studies of bats, where I will investigate how their 3D flight behavior changes under different experimental regimes.

How would you explain the main findings of your paper to a member of the public?

When bats echolocate, they do so by emitting a powerful transient call which propagates through the environment, reflects off a target of interest, and then returns as a much weaker echo a few milliseconds later. The whole process can then repeat as the bat uses the echoes from prey items to guide its target intercept. However, when bats echolocate, it is not only targets of interest which generate an echo – everything ensonified will provide echoes. These extraneous echoes, called clutter, pose an issue for bats as they can interfere with their biosonar operation. If bats call too quickly in clutter, they may run into a scenario in which they call before all echoes from the previous call have returned. Under such circumstances, bats face a conundrum: did the echo that just arrived stem from the current call and therefore from an object very close by, or from the previous call and as such is from an object far away?

Because of such range ambiguity, it has been a long-held belief that bats (as well as toothed whales) seek to avoid such range ambiguity by timing their call emissions such that all echoes from the first call arrive before the second call is emitted.

An alternative solution is to take advantage of the fact that call energy dissipates quite quickly in air, as it is diluted over an ever-increasing surface area and because it gets converted into heat as it propagates. As such, far away objects give rise to much weaker echoes than objects close by. By emitting weaker calls, bats can therefore in principle ensure that echoes from far away objects are so weak that they in essence are undetectable to their ears, and thus of no concern in an ambiguity context. We sought to test if bats, when faced with clutter, changed how often or how loud they called during a landing task. However, we found that they did neither and easily landed despite apparent range ambiguity. We therefore concluded that bats do not need to wait for all echoes to return to successfully navigate and that they are resilient to clutter.

Why did you choose JEB to publish your paper?

JEB has a stated emphasis of ‘elucidating mechanism and understanding physiological processes, responses to stressors and adaptions to diverse environments’ with ‘the single most important criterion for publication in JEB’ being ‘significant advancement of scientific knowledge’. Not only are these core values ones that align with my own, implicit in them and relevant to a lot of my work is that results need not be statistically significant to be of great biological relevance. What has held true for my MSc work and for two of my published PhD papers is that I investigated core ideas or controversies established in the literature, and set forth to test the predictions that arise from these hypotheses under controlled laboratory conditions. JEB’s willingness to publish results which are not statistically significant but are of great importance to the field because they challenge previously held notions is part of why I like publishing in this journal. Coupled with their open access policies where all papers are open access 6 months after publication, travel grants for early career researchers and a thorough but fair review process, and you have a journal with many admirable qualities and one which most journals should look up to and be inspired by.

What do you like to do in your free time?

I am an avid runner and I try to be active a few times every week. I have done everything from weekly park runs up to the half-marathon distance, of which I completed two last year. I hope to build up to the full marathon distance either in 2024 or in 2025. I also enjoy going for walks in the forest or on the beach while getting lost in a good audiobook, with ‘The Martian’ and ‘Project Hail Mary’ by Andy Weir being top choices to listen to.