Sunday 28 April 2024

Call of the Elephants

Arguably the single most significant feature that has enabled our own species to dominate the Earth is our possession of language. This enables us to communicate and cooperate to achieve things we could not do individually, to an extent unparalleled outside of social insects, which lack our ability for complex thought in other ways. Without language, it's hard to see how we would have built cities, or maintained the incremental advance in knowledge that has marked many thousands of years of our history.

Yet language, of course, did not arise from nowhere. There is an understandable interest among scientists in determining how it might have evolved, and what from. Since we can't go back in time to perform linguistic analysis on the likes of Homo erectus, one of our major sources of information is determining how other species of mammals communicate using sound, rather than the scent marks that are so important to many of them. Much of the focus here is on primates, since these are the most likely to hold clues to our own origins, but this can be extended to other species, too. To what extent do other animals have something that could be considered ancestral to language?

One way to look at this is to consider what makes language different from mere noise. If a human screams in sudden pain, that's communication of a sort, certainly, but it isn't what we'd call language. Language has to have structure and syntax. To find other animals whose communicative abilities are at least moving in the right direction, we need to find those that have moved beyond, say, a generalised alarm call.

The most advanced level of this would be the ability to string different calls together into a sequence whose combined meaning provides more information than the individual calls themselves - creating something that's analogous to a sentence. Chimpanzees have been reported to do this, although it's no surprise that they fall short of the grammatical structure that would typify a true language. Perhaps more surprisingly, the only other animals currently known to do this are both birds - the Japanese great tit (Parus minor) and the southern pied babbler (Turdoides bicolor).

A simpler level consists of combining sounds that don't mean anything of themselves in different ways to create structured calls with different meanings. In a loose sense, this could be thought of as a word, rather as "brick" and "crib" contain the same four meaningless phonemes in a different order but don't mean the same thing. This is still rare among non-human animals, so far as we know, but not so much as sentence-level syntax - we see it in gorillas, meerkats, and chickadees, for example.

Where else might we look for such complex communication? For a start, we need to look at social animals; any animal that lives most of its life alone won't need anything more complex than, perhaps, a mating call, a means to link up with its young, and so on. Cetaceans are an obvious example here, given their high reliance on auditory communication, large brains, and complex social lives. Another possibility is elephants.

There are three species of elephant alive today, two in Africa, and one in Asia. They fit all of the criteria that we also see in cetaceans. For instance, they do have large brains, not only in absolute terms, but relative to their body size as well. They certainly have complex social lives that in some ways mirror those of primates, and we know that they call to each other and can, for example, recognise the individual voices of their relatives and unrelated neighbours.

The most common vocalisation among elephants is a deep rumble - often so deep as to be inaudible to humans. It is these that allow elephants to vocally identify one another, with the low tone allowing the sound to be heard over long distances, so that they can, to an extent, keep in touch when out of visual range. The nature of the rumbles changes with the emotional state of the elephant, so that's at least part of what is being communicated. However, elephants also produce louder, higher-pitched roars or trumpeting sounds, which are much more evident to we humans and generally indicate that the elephant is distressed or angry. 

Previous studies have confirmed that elephants use these two vocalisations in combination but, from a linguistic perspective, the question remains whether this provides any additional information beyond what the sounds would mean on their own. Here, it's interesting to note that there is a difference between the three species. The two best-known species are the Asian elephant (Elephas maximus) and the savannah elephant (Loxodonta africana), which is what most people think of when they think of an African elephant. When they use the two sounds together, both of these species, it turns out, have a strong tendency to produce the roar first and then rumble.

However, this is not true of the other species, the forest elephant (Loxodonta cyclotis). This lives in African jungles, rather than the more open wooded country of the savannah elephant, and is generally less well-known, having only been identified as a distinct species in 2005. It is both the smallest of the three living species, and the rarest - and bear in mind that they are all endangered species, so this is significant. When it comes to the question of vocal communication, however, this appears to be more complex than seen in its more common cousins. Specifically, when using the two sounds in combination, they can be in either order, or even strung into three "syllable" structures with about equal likelihood.

But does this really mean anything to the elephants?

To try and answer this question, researchers used a treetop platform on the edge of a forest clearing in the Dzanga-Ndoki National Park in the southern tip of the Central African Republic, where a large salt lick sees elephants regularly gather throughout the year. From this vantage point, they were able to watch and record elephants visiting the site during the 2018-19 dry season, collecting 760 instances in total.

Looking first at the sounds produced on their own, the study confirmed what was already known. Low rumbles are the most common sound produced by the elephants, and can occur in a range of different contexts. Roars, however, are more specific, being used either when elephants were being aggressive towards one another (often, for example, when an elephant had been pushed away from a favoured salt lick, and was apparently complaining about the fact) or by young elephants calling out to their mother because they wanted to suckle.

Combination calls, however, were used in a wider range of contexts, but were more common in some than others. For example, elephants would both rumble and roar (seemingly in either order) if they became separated from their herd. There's some logic in this - the roar tells the herd that the elephant in question is distressed about something, while the rumble tells them who it is. If you're an elephant, you wouldn't want to go back for a stranger, especially when the stranger's herd is probably nearby anyway. Similarly, such calls were more common in aggressive situations, too, perhaps letting the elephant's allies know who it is that has got themselves in trouble.

But is this providing anything beyond what you'd get if the two calls were used separately?  It seems to me that that's a bit of a stretch, although the fact that the researchers didn't have enough data to check if rumble-roar was used in different contexts than roar-rumble or even rumble-roar-rumble may mean that there's some subtlety there we're missing. Indeed, the detailed analysis of the sounds they were able to conduct implied that they were subtly different when used in combination than when alone, which makes it seem more like the construction of words from individually meaningless sounds than sentences from meaningful words. They might, for instance, indicate mixed feelings on the part of the elephant, allowing their fellows to infer a more nuanced range of emotions than something like happy/sad.

So elephants cannot, at least on the basis of this one study, be added to the list of animals, like chimps and great tits, that can string sounds together syntactically to create new meanings. But the sounds they are making probably do convey more meaning than we would appreciate from listening to them in isolation. With just two types of sound, they can probably convey rather more than just two pieces of information.

[Photo by Matt Muir, from Wikimedia Commons.]

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