‘Animal communications evolved in their own world — human clamour now impacts this’

Nicolas Mathevon is Distinguished Professor of Neurosciences and Animal Behavior at the University of Saint-Etienne, France, and visiting professor at the University of California, Berkeley. Speaking to Srijana Mitra Das at Times Evoke, he discusses the world of animals speaking:
What is the core of your research?
I am a bioacoustician. I study how animals use sound to communicate. The idea is to understand how animals exchange information using sound signals and vocalisations. We record animals and analyse the acoustic structure of their sounds, searching for certain information therein. We have found two main types of information thus — static and dynamic. Static information is related to vocal signatures, like individual information, species and group identity, etc. Dynamic information is about an animal’s motivation, stress, etc. Using analytical tools, we quantify the acoustic features that carry such data. Once we identify a specific signal, we use this in tests, asking animals if the feature identified indeed carries such information and if an animal can use this to recognise its friends, family members and so on.

Picture courtesy: iStock


Does each animal have a special sound?
Yes. Consider the song of any songbird — the first information here is about the bird’s species. Each songbird species has its own song. Then, this has other types of information too — one is the individual identity of the singer, where it says, ‘I am so and so’. Territorial birds find this useful as neighbours who can identify each other’s vocalisation don’t need to fight and can live harmoniously. This extends to other animals as well. We have a research program on the elephant seal in California which lives in colonies on beaches. The males compete for females and the former have a very specific call, a ‘cluck-cluck’. Every male knows the voice of every other male. They can recognise their calls, which enables them to avoid fights because they know, for instance, ‘Oh, that’s Peter speaking’ or ‘It’s Paul calling’. They also know if the male speaking is stronger or weaker and can properly evaluate if a fight is even required. They can thus navigate the social system on the beach.

GOSSIP GIRLS: Information about food or predators often travels across species (Picture courtesy: iStock)

Do animals have languages — and why does this possibility generate so much debate?
That depends on what we call ‘language’. You could have a very restricted way of defining language, saying this is only human with very specific characteristics and a great deal of complexity through which we express almost an infinite amount of information. But just as humans live in their own world, each animal species inhabits its specific world. Each species’ communication evolved in this — if we use a less restricting defi-nition and say language is a system that uses sounds to exchange information, then you can say any species that has developed acoustic communications, which always conveys information, has a specific language. People get excited about this because many try to search for the same rules we find in human language among non- human animals. Interestingly, some features are shared by all beings, like the redundancy of information or the fact that we all repeat the same thing many times over. But specific rules do govern animal languages and the complexity of their acoustic system also correlates to their social system.

DID YOU SAY SOMETHING? Hippos identify friends’ voices, thus avoiding area fights (Picture courtesy: iStock)

Do animals convey emotions through sound?

Absolutely. You can classify these under dynamic information, related to the current state of the individual — this could also be its emotional state, be it courtship, hunger or happiness. Charles Darwin wrote about this and it’s been amply demonstrated since. Of course, anyone who has a pet dog or cat knows animals code emotional information in their voice. This is true for wildlife as well, who can also enhance their emotional coding. When birds give alarm calls, different birds repeat these — thus, information travels across landscapes. Once, we did an experiment with the black caiman in the wild. We played back distress calls from very young juveniles recorded before — the other juveniles responded by emitting their own distress calls. This increased the response of the mother who hurried back to the nest extremely fast.

How do animal parents communicate with their offspring?
Parent-offspring communication is widespread in species where there is parental care. In crocodiles, for instance, the female lays eggs in the sand and stays on the nest for three months. At the end of this duration, the eggs are about to hatch — but even before that happens, the young in their shells start emitting hatching calls. In reaction, the mother digs up the sand and takes the eggs in her mouth, helping the young escape the shells — imagine the enormous mouth of a crocodile, just gently cracking the eggs because she’s heard those calls. Parent-offspring communication is also very strong in birds. Interestingly, chicks who call most intensely for feeding receive the maximum from their parents. In mammals, we’ve found among fur seals, pups emit a call for the mother whose voice they can recognise. If a pup has been fed and you playback the voice of its mother to it, it won’t react much. After a few days, when it gets hungry, it reacts to its mother’s call but ignores other females. After a while, if the mother is still in the sea, an irate pup responds to all female calls until its mother returns and feeds it. So, acoustic communication between parent and offspring is very plastic — it depends on the situation.

Why should animal communication matter to human beings?
First, we humans want to understand the world in which we are and animal communication is simply fascinating. Second, we are interested in the evolution of human language. Analysing how animals communicate can give us some indications of how our own language evolved. There are practical applications too — if you understand the distress calls of birds, you can build tools to amplify these, which is done at many airports for safe take-offs and landings. In my lab, the French train company funds a PhD thesis, the goal of this being building systems to scurry deer off train tracks and avoid any accidents.


Are climate change and habitat loss now impacting animal communication?
Certainly. These are having global effects on all ecosystems which are altering the composition of animal populations — and their communication. The main impact now is human noise — our activities really disturb animals in the air, terrestrially and even more intensely underwater as sound travels very fast and easily in water. The sea is very noisy now with ships, underwater explosions, mining, sonar work, etc. These are damaging the hearing of whales and dolphins — and their extraordinary acoustic communications.

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