The black-capped chickadee is wonderfully onomatopoeic. When the diminutive songbird, which is Canada’s answer to the great tit, spots a great-horned owl perched in a tree, it broadcasts a shrill ‘chickadee-dee’ noise to highlight its disapproval. It’s unimpressed but not too alarmed, because the bulky raptor is slow and unlikely to cause trouble.
Then the chickadee spots a pygmy owl, also seated. This is a smaller, more agile predator, with a taste for small birds. In response, the chickadee ups the ante in the only way it knows how, adding an extra couple of ‘dees’ to the end of its call: ‘Chickadee-dee-dee-dee!’
The sound is an avian call to arms, signalling flock members to mob the intruder. All at once, half a dozen small birds dive-bomb, harry and berate the hapless raptor, which – if all goes according to plan – then skulks off in search of a quieter life. Danger is averted.
Versions of this story play out routinely in the woodlands of North America, providing a glimpse into the rich and varied world of animal communication. Animals communicate in many different ways, including sounds, smells and gestures. From the ear-splitting cry of howler monkeys in the jungle to the bellowing of deer in northern forests, from the calls of songbirds to the whistles of dolphins, from the clicks of sperm whales to the low-frequency rumbles of elephants, research is now revealing just how diverse, complex and nuanced animal communication is.
We humans may like to think that our communication system is superior, but the strategies evolved by other animals to suit them and their lifestyles are perfect in their own way, too.
The chickadee’s ‘chickadee’ is an example of a short, punchy vocalisation, known as a call. In this case, the number of dees correlates, literally, with the size of the threat, but this is only part of the little bird’s big repertoire. High-ranking males also make a gargling call to low-ranking males – back off, I’m the boss – while a high-pitched ‘see’ prompts birds of both sexes to freeze on the spot because a predator is on the wing. There are others, too.
The call of birds
Calls are thought to be largely instinctive but songbirds also sing complex melodies that have to be learned. This is another type of communication. Take the savannah sparrow, native to the grasslands of North America. Its song is a flute-like melody of chirps and trills.
At face value, this is a beautiful song but dig a little deeper – as Dan Mennill from the University of Windsor, Canada has done – and you find specific information encoded within it. The early part of the song is unique to the individual, the middle part is unique to the population, and the overall ‘theme’ is unique to the species. In other words, the first part reveals who the bird is, the middle bit reveals where they are from, and the whole thing shouts, “I’m a savannah sparrow.”
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In New Brunswick, where Mennill studied the birds, different populations living on different islands have different ‘bits in the middle’. This is the avian equivalent of having a dialect or accent – individuals can recognise each other by their songs and tell something of their provenance.
Birdsong, however, is not set in stone, and individuals can tweak their tunes to imbue them with extra meaning. For example, when one male chickadee sings over another male chickadee, and matches the pitch of his song, it is perceived as a threat. The original singer becomes agitated and, Mennill has shown, is subsequently less likely to mate with a female or maintain his territory. Birdsong, then, is a form of communication that is used to defend resources and attract mates, and the information encoded within these melodies is vital to that end.
“This shows us that animals aren’t just little robots out there, uttering beautiful-seeming songs. They are actually engaged in a kind of audio warfare, where particular signals uttered in particular ways make the difference between whether a bird wins or loses a territory or a breeding opportunity,” says Mennill. (In this respect, sound matters to many other animals, including the red deer stags that bellow aggressively to establish mating rights during the rut.)
Much of what we know about bird communication comes from playback studies, where researchers record vocalisations and then watch the responses as they are played back to an individual. There have been more than 600 of these, but the same approach has also been applied to other animals.
Communicating for sociability
From this, we have learned that elephants use specific calls – harmonically rich, low-frequency sounds – to address key members of their group. They appear to have names for each other. Bottlenose dolphins have signature whistles, sounds used by individuals to represent themselves. Other dolphins can recognise and remember these whistles for up to 20 years, and copy them as a way to address each other.
This makes sense. Elephants and dolphins are both highly social creatures that live in groups and cooperate to raise young, find food and safely get through the day. Being able to identify each other, especially over long distances or in conditions of poor visibility, is crucial.
Sperm whales are also social creatures. They live in tight-knit, female-led units of around seven or eight individuals, and they communicate with each other via patterns of clicks known as codas, made by the clapping of a pair of fibrous structures called ‘phonic lips’ located near the nostrils. Eavesdrop on a group of sperm whales using a hydrophone and you’ll hear almost constant chatter, like the back and forth of morse code.
Like dolphins and elephants, sperm whales have a part of their communication that signals their identity, but what’s strange is that they make these sounds when they are right next to each other – when visibility and distance are not an issue. “In this case, it’s not like a conversation,” says Luke Rendell from St Andrews University, who studies sperm whales. “It’s more like a duet.” Animals make the same codas at the same time, then pause and repeat, over and over.
In these instances, Rendell believes that the interaction has less to do with individuals identifying themselves and more to do with bonding. Sperm whales babysit for each other and work together to fend off predators, but only if their social circle is tight. “I do think there’s something deeper here about how sperm whales create and maintain the strong social bonds that they need to ensure their success,” he says.
Dialects of animals
Dialects are another feature of sperm whale communication. In the Caribbean, for example, each unit has its own repertoire of codas, including some that are unique to the unit and others that are shared with different units. For example, the ‘1+1+3’ coda, which sounds like a truncated ‘cha-cha-cha’, is unique to the Caribbean, where it has been produced in the same way for 30 years.
Collectively, units with shared dialects are known as ‘vocal clans’ and Rendell has found that, across the Pacific Ocean, there are just seven of these groups. This means that around a third to half of the world’s sperm whale population communicates using one of just seven different accents.
During their lives, sperm whales can travel hundreds of thousands of kilometres, and meet many different whales, but units only ever spend time with other units that are part of the same vocal clan. Researchers think this is because the dialect is a shorthand for ‘we will cooperate’. Sperm whales appear to have evolved a way of organising their society that lets them gather together rapidly, potentially with individuals they’ve never met before, to defend themselves against predators such as orcas and large sharks.
'Singing' species
Humpback whales, meanwhile, don’t click – they sing. “They have one of the most complex acoustic signals in the animal kingdom,” says whale researcher Ellen Garland, also from the University of St Andrews. Unlike sperm whales, explains Garland, humpbacks are usually solitary. It is the males who sing, ostensibly to attract a mate. Their haunting vocalisations, which fall within our hearing range, are made of units – things like moans, groans and whoops – combined to form phrases, repeated to make themes, incorporated into songs, which can last for up to 20 minutes and be rebroadcast for hours on end.
Research from Garland and others has shown that in each population, at any point in time, all of the males sing the same song, but that the song is constantly evolving. Sometimes this evolution happens slowly, across decades. But at other times there is a ‘song revolution’, where an entire melody is replaced over the span of a breeding season or two. This process of sudden change has been likened to Beatlemania back in the 60s, or the fickle whims of human fashion. More than 22,500km-worth of song transmission has been tracked. It’s thought that this process is driven by the males’ desire to conform – to detect and copy any differences they hear – and the females’ desire for song novelty.
According to Garland, the complex song communicates something along the lines of, “I’m a mature male. I’m here. I’m ready to mate.” And, because there is cultural conformity within each song. “I’m one of you.”
Do animals have language?
With all this complexity, you’d be forgiven for imagining that whales, and maybe other animals, possess language. Indeed, Garland has recently found that humpback song contains a human language-like structure, while sperm whale vocalisations have been shown to be more expressive and structured than once thought.
But just because an animal’s vocalisations are complex and have language-like elements within them, it doesn’t mean that they are conversing like we do. “This is absolutely not language,” says Garland of the humpback songs. Though the vocalisations may convey information, they don’t have semantic meaning in the way that human language does. To put it another way: though they may have building blocks that are a bit language-like, there is, at present, no evidence to suggest that whales – or any other animals – recombine and use the building blocks of their communication like we do when we talk to one another.
“I think it’s a fool’s errand to try to map animal communication on to human language,” says Mennill, “or to imagine that animal vocalisations are the equivalent of a word or a sentence.”
From the songbirds of Canada to the elephants of Africa, the bottlenose dolphins of Scotland to the humpback and sperm whales traversing our oceans, different species have evolved their own ways of communicating the things that are important to them. Every strategy represents a unique solution to a unique set of problems faced by the animals in their everyday lives. As a result, what they ‘say’ is as distinctive as the animals themselves.
Mennill says it best. “I think we need to have our ears open and understand what they’re doing on their own terms. If we can do that, it will be the way to develop a much deeper appreciation of the complexity of animal communication.”
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Top image: two African elephants. Credit: Getty
