A pandemonium of parrots, a cackle of hyenas, an exaltation of larks — these are just a few of the animals that we define by the sounds they make.
For humans, communication is the bedrock of our relationships and part of how we successfully function in our daily lives. Animals make sounds to issue warnings, attract mates, signal distress, find one another and defend their territory; similarly to us, their vocal chords fulfill myriad purposes that lay their social foundations and ensure their survival.
But have you ever wondered, of all the creatures we share our planet with, which one vocalizes the most? And what value is there in being a chatterbox, when making sounds also carries a risk of alerting predators?
In human terms, we might measure "chattiness" in two ways: the amount of time spent vocalizing, and the diversity of what's communicated by those sounds. How does this apply to nonhuman species? Researchers have identified some common trends in species that vocalize a lot, and common trends in those that prefer quieter lives.
You might assume that one driving factor of animal communication would be how social the species is. It's true that some highly social species are also more voluble; for example, flocking birds such as quelea are constantly cacophonous on the wing. Then, there are mammals like the meerkat, a small, mongoose-like creature from southern Africa that lives in large, gregarious communities that cooperatively raise young, forage and look out for predators.
"When they're foraging, they're always chirping away, just so everyone knows, 'I'm here; it's me; everything's OK; there are no predators around.' They're constantly making this soft, gentle contact call," said Arik Kershenbaum, a zoologist at the University of Cambridge in the United Kingdom who studies animal vocal communication and uses algorithms to analyze and compare their sounds.
But this isn't a rule; being social doesn't necessarily mean an animal communicates a lot, Kershenbaum told Live Science. That's because vocalizing also comes at a cost. "Most animals try not to vocalize too much, because it actually requires a lot of energy," said Kershenbaum, who is the author of the book "The Zoologist's Guide to the Galaxy (opens in new tab)" (Penguin Press, 2021), part of which delves into animal communication.
Another factor is predation: Sounds put an animal at risk of potentially being caught. These two features place powerful pressures on the vocal communication of even highly social species, like the chimpanzee, one of our closest living relatives. "Chimpanzees vocalize very little, not as much as you would expect, given the complexity of their social groups," Kershenbaum said. To keep audible communication to a minimum, they often use gestures to communicate instead.
However, vocals aren't necessarily the gold standard of animal communication. "Animals are constantly broadcasting information, whether it's vocal, olfactory, through posture — it's all being assessed by other animals, who form an integrative idea of what to do and how to interact with this individual," Kershenbaum said.
When it comes to vocal communication, social species tend to have a greater diversity in the messages they convey, Kershenbaum said. As a general rule, animals that are solitary need to communicate simpler messages to the rest of the world, compared with animals that live in cooperative groups where communication is necessary to maintain social hierarchies, locate and share food and alert one another to threats. "You can see that if you're in a cooperative group, there may be more to say than if you're living on your own," Kershenbaum said.
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However, it can quickly become tricky territory when we try to dissect what animals are "saying" when they vocalize. One reason for this is that humans make the mistake of judging animal sounds by our standard of what counts as communication — specifically, through the framework of words.
There is evidence that some animal calls have specific meanings (a type of information researchers call referential communication) that could be considered word-like. For example, some monkeys issue specific alarm calls that signify a predator threat, and dolphins have distinct whistling sounds for different relatives. "They use this particular sound as a name, which could be considered a word," Kershenbaum said.
But these utterances occur only in scenarios where a single sound is the most efficient way to communicate one specific thing, he said. "I think it's, in general, a mistake to look at animal communication as being made of words," Kershenbaum said.
So, animal communication doesn't consist of discrete "words" with unique meanings, like our speech does. That idea is borne out by songbirds; although they have some of the most complex vocal sequences of all living things, these sequences usually occur in scenarios where the relative simplicity of what the bird needs to communicate — like calling for a mate or defending its territory — doesn't match the mind-boggling diversity of sounds that each call contains, Kershenbaum explained. So what's going on here?
One theory is that the medium itself is the message. Effectively, birds could be saying, "Look what a complex song I can sing! That means I must be a really good father," Kershenbaum said. In some sense, vocal acrobatics may be a substitute for colorful plumage, which is another way birds attract mates.
In fact, "Some species of birds, like mockingbirds or African gray parrots, steal sounds from other species out in the wild to sound smarter, so to speak," says Erich Jarvis, a neurobiologist at The Rockefeller University in New York who studies songbirds as a model for how humans learn to speak. Those parrots and mockingbirds suggest that individual vocalizations probably aren't communicating discrete messages in the way words do when humans speak; because they're lifted from a completely different species, they’re unlikely to have transferable meanings. It’s more likely that these are just new sounds that have been added to a vocal repertoire, rather than sounds with individual significance.
Although animals may not be saying multiple discrete things in the way our speech does, their vocalizations are nevertheless rich and dense with meaning.
Listen and learn
Whatever animals are saying, some spend a lot more time vocalizing than others. So who are those chatty individuals, and what makes this blabbing worth their while?
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According to Jarvis, animals can be split into two broad groups: nonvocal (or "innate") learners, and vocal learners, animals that learn to vocalize by imitating sounds. Only a few groups of animals fall into the vocal-learning camp: humans, songbird species, and some nonhuman mammals, including dolphins, whales, elephants, seals and bats.
"What's curious," Jarvis said, "is that those animals that have vocal learning are also some of the animals that are vocalizing the most." He also found that these animals are more likely to make more complex vocal sequences.
Jarvis is interested in why these vocal learners vocalize more often, and more complexly. On one hand, there's a huge advantage to vocalizing a lot. For starters, sound travels over long distances, so communicating more frequently can aid communication over large areas, helping animals lay claim to territory or find a mate. Being more voluble and making more complex calls also enable some animals to convey more information to others about their status. On the other hand, there are the aforementioned risks of vocalizing more: Making sound uses energy and attracts predators.
Jarvis hypothesized that the most vocal animals are typically the ones that have to worry less about predators. Interestingly, he noticed that especially voluble vocal learners "tend to be near the top of the food chain — like humans, whales, and dolphins or elephants. Or, they're vocalizing in the ultrasonic range [so can't be heard], like bats," he said. "Amongst the birds, we found that the parents in the songbirds were descended from apex predators. So their ancestors were at the top of the food chain. So I think they overcome predation and then get away with vocalizing a lot."
What's more, especially chatty animals have a system that minimizes the associated energy costs of constantly making sounds. Muscles in the larynx — aka the voice box — of vocal animals take up some of the largest amounts of energy in the body, and their activities require fast-firing neurons to control vocalizations. In turn, the activities of those neurons can generate toxic byproducts, similarly to the production of lactic acid, by working muscles that then need to be cleared away. Jarvis explained that vocal animals, including humans, share protein molecules that protect these fast-firing neurons from a toxin overload. "So us humans and songbirds and parrots and others have independently evolved mechanisms to protect our vocal pathway neurons, so that we can communicate a lot."
In other words, for highly vocal species, vocalizing confers a huge advantage, with relatively little cost. There are exceptions to this, however; for instance, zebra finches are vocal learners that vocalize only a little. "But on average, the vocal learners have a more complex vocal repertoire," Jarvis said. "Those who are vocalizing the most in terms of time are the ones who, on average, are producing more complex vocalizations."
So, who takes the crown for chattiest animal? "Nobody I know has really gone out there and quantified all the species to say that this is the case" — but the short answer would be that it's a member of the vocal-learning species, Jarvis said. Kershenbaum made an educated guess that among these vocal-learning animals, dolphins would be strong contenders for the title, based on his research. "If you are ever in the water with dolphins, it's almost never quiet," Kershenbaum said. They're always, always vocalizing."
Jarvis now devotes part of his research to investigating what vocal learners can tell us about human spoken language: He has identified certain genetic mutations in vocal-learning songbirds that could shed some light on how speech disorders occur in humans. So studying how animals communicate is more than just a curiosity; it could help us understand ourselves.
Originally published on Live Science.