A male koala let out a deep growl, as if it were huge. Or the chirping cheetah, which sounds like a harmless bird rather than a dangerous feline. The vocal repertoire of animals is much larger than we usually think. This is partly because bioacoustics, the field that studies animal sounds, is in full development: new measuring tools and research methods are still being developed. But there is another reason, confirms the Austrian animal behavior biologist Angela Stoeger (1976), who specializes in bioacoustics. “We are simply not used to really listening to nature. We often think of animal sounds as background music rather than a form of communication. Especially when it comes to sounds we don’t know.”
In her recently published book Around mice sing and elephants squeak Stoeger reported on two decades of animal vocal field work, with matching vocal fragments. If you want to hear the high-pitched guinea pig-like sounds of elephants, or the ngwèh-ngwèh cries of newly hatched Nile crocodiles, you can scan the QR codes scattered next to the text.
The roar of the koala in your book sounds majestic. Why would such an animal do that?
“Male koalas don’t roar all year round, only when they’re ready to mate. Then they put out a call around 30 Hz, if you’re standing in the eucalyptus forest which sounds pretty impressive. The low pitch ensures you can hear it over a long distance, but there’s also a competitive element to it. Males of low-voiced animals also often have more testosterone… The deeper the roar, the more attractive the females are.
“The koala’s vocal cords are too small to produce this deep sound. But two British biologists have revealed the secret: the folds of the soft palate, near the throat, are exceptionally large. When you inhale, the folds of skin contract, so that they can vibrate as if they were also your vocal cords. “.
In 2005, I accidentally discovered that an African elephant in the zoo also squeaked
You do a lot of research on elephants. What sound do they make?
“They cover a very wide repertoire, from a barely audible clatter around 20 Hz to a high-pitched guinea pig-like screeching. They make those lower notes with the help of their trunk. It’s infrasound, felt and not heard, like the tremors of an earthquake. This allows them to communicate with each other over miles away.
“Loud squeaks allow elephants to hear when they are excited about something, for better or for worse. This squeal can be around 2,000 Hz, which is impossible for their 15-centimetre-long vocal cords. They do this by vibrating their lips, like trumpeters.
“At first, this high-pitched sound was known mainly from Asian elephants, but in 2005 I accidentally discovered that an African elephant in the zoo also squeaked. It turned out to be imitating the behavior of two female Asian elephants he had lived with for years. Asian elephants seem to be among themselves often What squeals learn from family members. Therefore, elephants, like humans, are able to learn a vocal repertoire.”
Some species of birds adapt their song to background noise, for example by singing loudly
Is animal language similar to human language?
Linguist Noam Chomsky defined language as the biological characteristic of living things. Just like us, animals produce sounds to communicate with each other, with or without vocal cords. Human language is unique in the way we develop and use it, but you can say the same for many animal languages. Different types have different skills. We are good at combining sounds and giving them meaning. But we cannot, like elephants, communicate with relatives miles away without technological means. Or mosquitoes catch our voices, as bats do.”
Read about language in cows: “What this cow wants to ask me now is actually: Who are you?”
What do we not know about animal noises?
“Wow, so much. We don’t yet know the vocal repertoire of many species at all. And take that chirping cheetah. We have no idea why it sounds like a bird. It’s probably a form of vocal mimicry, as it mimics another species on purpose to protect itself from enemy lions.” But more research is needed.
We also know little about the sounds made by insects or amphibians. And some sounds may not yet be heard with current measuring equipment.”
What would the perfect voice recorder look like?
“A combination of GPS, audio and video would be best, so you can tell who is making what sound and when. But at least as important as developing good algorithms for sound analysis. You can also use noise monitoring as an early warning system to prevent conflicts between Humans and wild animals. If you hear that a herd of elephants is approaching, the villagers might be able to get to safety in time.”
I wanted to investigate how noise pollution affects marine mammals
Do animals suffer from noise pollution?
“Absolute. First of all, they have to communicate louder to make themselves heard, and that takes energy. Some bird species adjust their song to background noise, for example by singing louder or at a different time. Or they leave for another area. It’s known Mammals also adapt their activities to the amount of noise, but not all groups of animals are so resilient.
“And the worst thing is that noise is everywhere. From oceans to safari parks, there is no escaping it. There is still little concern for noise pollution. Under water, animals can be thrown off course by low noise from container ships. It is already known in In the North countries wolves and reindeer keep away when windmills are erected. The animals do not have noise canceling headphones with which they can simply turn off the sound.”
What animal sound is still on your wish list?
“That manatees! They are closely related to elephants. As a child I was fascinated by marine mammals. I grew up with TV documentaries of marine biologist Hans Haase, a sort of Austrian Jacques Cousteau, and by the age of 10 I knew all the names of whales by heart.” In the 1980s Scientists have just discovered that whales can sing.
“During my studies I chose all subjects of marine biology, even though I live in a country four hours away from the nearest sea. I wanted to investigate how noise pollution affects marine mammals. But then a professor came and asked if I wanted to do research in acoustics The vitality of elephants. At first I thought they were big, gray and boring, but soon it closed in on my heart.”