Hearing the first chiffchaff: for many birdwatchers it is the start of spring, because the birds start singing so early in the year and because their sound (‘chiff-chaff-chiff-chaff’) is so easy to recognize. Certainly for an acoustic ecologist like Hans Slabbekoorn (1967), who has been working with nature sounds for almost his entire career. Yet this year he only heard his first chiffchaff about three weeks after the first had arrived in the Netherlands from the south. “I was simply not outside enough. Too much behind my computer.”
Slabbekoorn was busy. With the preparation of his inaugural lecture, in honor of his professorship of acoustic ecology and biodiversity at Leiden University. By setting up a partnership with the Surinamese Anton de Kom University. And by arranging the Migradrome, a seven meter long tunnel in which, after installation, all kinds of acoustic experiments with fish can be done.
Because although Slabbekoorn still has a soft spot for birds, he is no longer just the ‘great tit man’ who made the news twenty years ago with his discovery that city birds start singing higher to get above the traffic noise. His focus has increasingly shifted to underwater sounds and interdisciplinarity, he says from space where the Migraddrome will soon be built.
Our wish is to create a more natural environment, a small river
There is not much more to see than a white room with an electrical outlet.
“True, but in a year we hope to have a transparent, water-filled research tunnel here with ten loudspeakers, five cameras and two pumps that are specially placed behind a wall so that they do not make any noise. A test river in which we can investigate the influence of sound on migrating freshwater fish. We now also have aquariums in the adjacent lab, with sticklebacks, but our wish is precisely to create a more natural environment, a small river. Underwater noise can have such a big impact on marine life – for example, we already know that cod become less active during the construction of offshore wind farms and leave the area early.
“Sometimes I get the question: what do you do as a bird man among the fish? But noise pollution is everywhere. By the way, water birds also suffer from that underwater noise. Once off the coast of Ireland I was riding a RIB, a cross between an inflatable boat and a speedboat, and in the distance I saw a cormorant surface and flee.”
It was all quite technical and I’m not much of a beta person at all
How did your interest in bioacoustics come about?
“For my PhD research, I researched the acoustic communication between turtle doves, which I found extremely interesting, so I took it further. I really had to master those research methods with sound, it was all quite technical and I’m not much of a science person at all. In fact, in high school biology was the only subject I got a 5 for. And during my studies I often had to redo the physics and chemistry subjects. But the love for nature was so deep, I had inherited it from home, that I knew what I wanted to fight for.
“I now know: you don’t have to be very good at everything, as long as you can play your part. Science is real teamwork. It is precisely this interdisciplinary collaboration that appeals to me. I am not only referring to collaborating with colleagues from other faculties, but also with the offshore industry and fisheries, for example. And on politics, because you naturally want all ecological research to be implemented as directly as possible in the reports and guidelines of the ministries. So that it is not only said afterwards that ‘this could have been better’, but that adjustments are made at an early stage on the basis of ecological insights.”
We walk from the space of the future Migraddrome to Slabbekoorn’s office. On the cupboard is a fake heron brotherly next to a fake blackbird and a fake stork, the wall is decorated with children’s drawings. “They have been hanging there for a while, my children are now 20 and 18…”
In your inaugural lecture you emphasize the importance of fieldwork. You have done fieldwork in Ecuador, Colombia and Cameroon, among others, and yet you now spend so much time indoors as a professor.
“Yes, but fortunately, besides animals, people are also my motivation. I do less research myself now, but I also really enjoy supervising PhD students. We are now setting up a multi-year program with the Anton de Kom University in Paramaribo. Biology has only been an official bachelor’s degree there for a few years and we want to do joint field research in the field of bioacoustics and environmental DNA, i.e. environmental DNA from mud, dust, water and excrement, for example. Collecting both sounds and e-DNA is a non-invasive way to sample an area, and both methods complement each other: you can find out which species are present there and what exactly they are doing there.”
Leaf blowers! I live in Amstelveen and those things frustrate me enormously
He pauses for a moment. “And it will therefore really be a collaborative project, with respect for each other’s knowledge and each other’s history. I miss that collaboration in many places, including in the Netherlands. Now, for example, it seems as if farmers and nature lovers are diametrically opposed to each other, while those polarizations and contrasts are unjustified. I grew up in Zeeland, between farmers and fishermen, my grandfather was in fruit cultivation. I feel connected to nature, the city and the countryside, but I miss the dialogue.”
As an acoustic ecologist, what is your least favorite sound?
Full of conviction: “Leaf blowers! I live in Amstelveen and those things frustrate me enormously. Not only because they regularly turn a residential area into a motocross track through their noise, but also because they remove the bottom layer of the food chain, the litter layer. Benthic life is disappearing, so the birds are also staying away, even though a rich biodiversity is also important for our own well-being. Don’t get me wrong, I don’t want to correct the employees of the parks department, they have a lot of practical knowledge and they also love nature. But I would love to work with them so that we can achieve more ecological management.”