Wolves’ howls are eerie, beautiful and wild. But what are they actually saying to each other?
As the heroes fled the dark castle for the darker woods, Count Dracula’s ‘children of the night’ began to make their ‘music’: a distant chorus of lupine howls, echoing through the Transylvanian night. I paused the movie. ‘That’s not a European wolf, the howl’s all wrong!’ I told my long-suffering companion. ‘That wolf belongs in the backwoods of California!’
After hundreds of hours listening to thousands of wolves for my PhD, the difference between howls was obvious. The voice of a Russian wolf was nothing like that of a Canadian, and a jackal was so utterly different again that it was like listening to Farsi and French. I believed that there must be geographic and subspecies distinctions. Other researchers had made this proposition before, but no one had put together a large enough collection of howls to test it properly. A few years later, my degree finished, I told my Dracula story to the zoologist Arik Kershenbaum at the University of Cambridge. He promptly suggested we explore how attuned to wolves I really am. Are there differences between canid species and subspecies and, if so, could these reflect diverging cultures?
When animals call to each other, they are communicating in a single stream of information from caller to listener. Until modern recording technology was invented, any acoustic communication lasted only as long as the echo. So while we can hear difference in modern human speech, with more than 6,000 extant languages and an unknowable number of local accents for each language, we can’t trace the origin of language from before writing or know how ancient peoples would have sounded. Before 1860, when de Martinville made the first acoustic recording, the world of speech must remain silent to us, though we can sometimes hear scattered fragments of dead languages still alive in our own.
The question of when and how language first emerged is the topic of tremendous controversy – it has even been called ‘the hardest question in science’. My work is on what information can be extracted from vocalisations. It is a first step in understanding where the physical body dictates the shape and form of the call, and where the caller has control. For example, a piano player is limited to combinations of a piano’s 88 keys, but a song played on a Steinway will have different sound qualities to the same song on a bar’s upright. In addition, different tunes can also be played. Separating the characteristics of the instrument from the choices of the player is essential before we can understand what meaning those choices might convey.
Behaviour is not purely instinctual, bred in the bone and performed from birth without thought or flexibility. It is often learned socially. Chimpanzees are a fascinating example: their use of tools spreads from one individual to another as they copy the successful tactics of their troop-mates in breaking apart nuts, catching ants or cleaning their teeth. They’re shown to prefer cooked food over raw, and are even able to learn US sign language. All this has increased interest in how other species develop shared cultures and knowledge. Whether it’s tool use in birds, farming by ants, or dancing in parrots, activities that were previously believed to be specific to humans are now being found in a variety of species. This means that animals can be used as a model for humans, allowing us a window into an otherwise cryptic part of our own evolution.
Perhaps the most fascinating area of this research is the evolution of language and speech. It was once believed that only humans used language and that animal sounds were nothing more than instinctive responses to behavioural cues, such as cries of pain. Now we know that many species have flexibility in their vocal production, allowing them to choose when to call and what sound to make. Researchers have found that monkeys use different calls for different predators, and that prairie dogs can encode the colour and shape of an approaching predator in their alarm calls. Songbirds display particularly complex rules to the order of their singing notes. The hope is that studying animal calls will shed light on the way human speech developed. It’s a step toward solving the hardest question in science.
Dialects, or regional differences in the form and use of vocalisations, have been observed in birds, bats, chimpanzees and now an increasingly long list of other species. This has been most beautifully heard in whales, where the songs of humpbacks are transmitted across hundreds of miles, telling a listener which part of the ocean the whale lives in, and tracing its family group by the influences on song formations. The bioacousticians Katharine Payne and Roger Payne first listened to the whales on underwater microphone recordings in the 1960s, and used musical notation to explore the changes that occurred in each male’s song, year on year. Whalesong, heard by humans as long ago as Aristotle, became the subject of intense study and public interest. Their research showed that there were geographic differences in humpback whale songs and that we could tell apart populations just by using those songs, which change throughout their lives. So the whales were controlling their singing and subject to cultural influences. The Paynes had found dialects in whale song. Would we find the same for canids?
Despite their cultural popularity, wolf howls haven’t been the subject of focussed research until recently. Now, following the lead of marine biologists and ornithologists, and with improved sound recording equipment and analysis programs, researchers can study them in depth. The first step in understanding what animals are saying to one another is to figure out what aspects of the voice are functional and what parts are formed by the structure of the throat and mouth, or what is the piano and what is the tune. Studies since the 1960s have shown that the howls that have haunted our dreams for centuries can tell us a lot about the particular wolf vocalising. Like humans, each wolf has its own voice. Each pack also shares howl similarities, making different families sound distinct from each other (wolves respond more favourably to familiar howls). This much we knew. What we didn’t know was whether the differences seen between packs were true of subspecies or of species, and if an Indian wolf howl would be distinct from a Canadian one.
More questions follow. If howls from different subspecies are different, do the howls convey the same message? Is there a shared culture of howl-meanings, where an aggressive howl from a European wolf means the same thing as an aggressive howl of a Himalayan? And can a coyote differentiate between a red wolf howling with aggressive intent and one advertising the desire to mate? Even without grammar or syntax, howls can convey intent, and if the shape of the howl changes enough while the intent remains constant, the foundations of distinctive culture can begin to appear.
The wolf species were like music bands with preferred styles of playing: riff-filled like jazz or the pure tones of classical
To explore this, Kershenbaum brought together a group of researchers to share data and ideas. We compared howls across 13 different subspecies and species of coyotes, dogs, wolves and jackals (collectively known as canids). The howls came from my own recordings on chilly evenings in Poland and Russia; from UK zoos and conservation sites (where I howled at the bemused wolves and listened in awe as they responded); from our co-authors in the US, Spain and India; from historic recordings taken across continents and time; from the public, in the form of hundreds of YouTube videos of howling pets. Our canine voice collection represented was one of the most comprehensive ever.
We then stretched all the howls to the same length, using a process called dynamic time warping, to compare the changes in the tune without including the tempo it was played at. We found that each species had its own favourite howl shape, a preferred set of changes to their howls to raise and drop the pitch, but that they also used howl shapes preferred by other species, and varied the shapes as they pleased. The species were like music bands with preferred styles of playing, whether riff-filled like jazz or the pure tones of classical, but were flexible in what they actually played at any given time. So while they had a favourite style, the tune itself varied.
Like musicians, the wolves were influenced by their forebears in the genre, and species shared traits with other canids that were closer to them geographically and genetically. An Eastern grey wolf, recorded in the US, sounded more like a North Carolinian red wolf than a European wolf, and an African jackal sounded quite different again. Small and delicate compared with their cousins the European wolves, golden jackals have high, rising howls, running up and down the scales in bravura performances of control and speed, but with less variation in overall shape, whereas the European wolves used a slower style of deep and steady long notes ending in falls that seem to drift away into the night. New Guinea singing dogs earned their names with a large vocal repertoire and a wide selection of howl shapes. While sometimes the different species achieved crossovers to other shapes, most had a style that dominated their repertoires.
If these differences across species sound familiar, they should. We’ve known for thousands of years that birdsong is distinct to each species, and sometimes even populations, with a nuthatch’s wha-wha-wha very different to a robin’s whistling call. We’ve seen that birds have adaptable repertoires, literally changing their tunes as new sounds become popular and spread through populations. Humpback whales sing new songs when they hear them, collecting new patterns of song throughout their lives and passing them on to others in their population. Our canid study showed that they had different howls for their species, but we have yet to answer whether they can change their howls with time or exposure to different howl patterns. Now that we’ve seen there are differences, the next question to answer is whether they are innate or learned, and how far a wolf can change its howl.
To understand how well wolves maintain their own styles when exposed to others, we did a smaller analysis of red wolves, Eastern grey wolves and coyotes. Wolves across the world are subject to conflict with humans, and red wolves are critically endangered with numbers that were once as low as 20 individuals in the 1970s. Huge effort has been put into saving the red wolf and returning it to its old hunting ranges of the southeastern US. But these wolves have a worrying propensity to mate with coyotes and interbreed with Eastern wolves, resulting in fertile hybrids. We hoped that the red wolf would have its own robust howl shape, separate from its neighbours’ and as distinct as the blues are from pop, which might mean that wolves could create their own communicative barrier to reproduction.
Unfortunately, that wasn’t the case. Like any good musician, the red wolves were not averse to using novel styles, and we found that they fitted at a midway point between coyote and Eastern wolf howls, showing that the howls wouldn’t form a barrier to their breeding. As the red wolves we studied were as genetically pure as possible, this suggests that they might be influenced by both coyotes and Eastern wolves, copying the sounds they hear around them. Or perhaps they never had a distinctive, red wolf howl shape and simply shared that of their near relatives. We will never know if there were other howl shapes of red wolves that were overwhelmed by hearing coyote and Eastern wolf howls too often – as lost today as early delta blues recordings – but the modern differences aren’t stopping cross-pollination for both sound and puppy creation.
The range of howl shapes we found is enough to encompass a large number of possible meanings. However, a howl is by its nature a public shout, not a private whisper, and that limits what is likely to be communicated. We can guess, but don’t currently know, what these meanings are. Perhaps there are subtle differences between ‘All pack come here’ and ‘Brother wolf here’, and potential vast differences between ‘Stay away, stranger’ and ‘Good food here, sister’. Beyond the interests in language, this matters to conservationists, some of whom have tried to protect livestock by playing recordings of wolf howls to scare away local wolves, but they might be using howls that ring the dinner bell instead of sending a keep out signal.
Is the territorial ‘get off my forest’ howl different to the lonely hearts ad of a lone wolf?
Some of these howl shapes were shared across species, while others were distinctive. While some of these differences between species might be the result of genetic drift, random mutations leading to changes that spread throughout a population, they might also develop in response to need, or to the shaping influence of the animal’s habitat. Where calls are flexible and shift with new experiences, as in the humpback whale song, they can be used to illuminate the possible evolution of language. Human accents and word usage shift as the speakers come into contact with new ideas and they adopt new sounds, sometimes a little mangled, into their own vocabulary.
The next step is to show whether there are behavioural contexts to howls, demonstrating if wolves, like other animals, can convey emotional states and information to their listeners, whether a territorial ‘get off my forest’ howl is different to a lonely hearts ad of a lone wolf searching for a new mate, whether a call to the hunt differs from the advertisement of a successful kill, and whether pups must learn these shapes or know them by instinct. We’ll also explore how long these differences persist through time and why some howl shapes are shared.
The howl isn’t an example of true language as humans understand it, with syntax and grammar where a single additional sound or stress can change a phrase’s entire meaning. However, if we can show that howls are not an instinctual but a learnt display, it will give us another potential piece of the puzzle of language evolution. Wolves and humans both act cooperatively, living in complex societies with multiple individuals in close association and where there are great advantages to communicating complex meaning. Humans use language to convey meaning through a huge variety of sounds, but proto-words probably developed in association with very basic ideas and intents that then evolved towards complexity. More closely related languages tend to be more similar, with French and Italian sharing enough words to be intelligible, but incomprehensible to speakers of Hindi, yet they can still all be linked back to a proto-Indo-European language.
Isolation and geographic distance have meant that human language has diverged multiple times, creating thousands and thousands of dialects, many with words distinct to the environment in which they arose. Yet certain words are so basic that they have barely changed over thousands of years, eg the word mother, which is ‘matar’ in Sanskrit, ‘mater’ in Latin and ‘meter’ in Ancient Greek, and ‘mzaa’ in Swahili. The word shows its original roots in a possibly universal proto-language even today, while the words for more complex ideas are more typically unrelated. Perhaps the wolves mirror us, the shared howl shapes representing a similarly universal concept as mother, with the more divergent howls relating to local concepts. By exploring this, we can explore the first steps towards true language.
Have wolves evolved to convey meaning in their calls? I don’t know for sure, but I think so. To my ears, a happy wolf surrounded by a pack has a very different howl to a lone voice crying in the wilderness, and a love duet with a mate does not match the chorus howl made with the new pups raising their tiny heads to the sky, but all the sounds are beautiful. Perhaps one day we will even understand their meaning. For now, I can only do as the wildlife ecologist Durward L Allen described, and listen ‘for a voice crying in the wilderness, and [hear] the jubilation of the wolves!’
is a postdoctoral researcher at Syracuse University in New York, where she studies wolves, conservation and large mammal biology.