While observing a group of Bonnet Macaques in Tamil Nadu I was fortunate enough to have captured the above clip. The Macaques initially appeared preoccupied with the passing traffic but occasional glances can be observed amongst members of the group. While a young macaque plays on the ground a sudden vocalisation can be heard amongst some of the other macaques which quickly spreads throughout the group. They are then observed to look in the same direction and exhibit a synchronous vocalisation. Although the reader on watching the video might seem it was rather obvious that something was afoot its interesting to take a step back and examine what was going on. I was rather a little surprised by the sounds that were coming from the group and looked around to see what they were looking at. That’s when I caught sight of the bird. Due to my lack of knowledge in this area I’m a little embarassed to say that I wasn’t quite sure what the bird was even after reviewing the footage. Unfortunately with regards to the footage of the bird it is of a very poor quality. The reader will be able to make out that the wings are of a grey colour, there is an orange colouring in the head area and a white colouring of the underbelly. The bird is seen soaring before disappearing firsly obscured by the nearby bushes and then finally over the hill. A local person suggested that it was an eagle (A list of birds in Tamil Nadu is given here and there are a few possible matches including one type of falcon and several types of eagle).
What was interesting was that on hearing the macaques my first thought was ‘what’s going on here?’. In other words it was enough to attract my attention. I imagined that the collective vocalisation of the group might be more intimidating to a bird of prey than that of a single individual within the group. The Old World Monkey ancestors diverged from our ancestors some 25 million years ago. Perhaps at that time our ancestors had already established that by collectively vocalising they would be more effective in warding off predators and thereby increasing their collective chances of survival. Thus there is a behaviour that is contingent on that of others in the group that potentially improves fitness. As an interesting aside the old world monkeys are arboreal and perhaps our own ancestors faced conflict with birds of prey during our evolution. In contrast the large greater apes wouldn’t have made easy targets.
So a second thought I had about the vocalisations was my own response. Could it be possible that there was some vestigial response that I had to these macaques – a useful remnant from millions of years of evolution – a conserved function if you will – that I would immediately recognise the warning signs that danger was approaching? A closer examination of the vocalisations (and readers can correct me) included a low-pitched ‘barking’ and a high pitched brief vocalisation. I wondered if the latter was the equivalent of a scream in a less powerful member of the group, while the more powerful members exhibited the barking sound – which I interpreted as an aggressive sound. In any case the bird quickly disappears.
The question this clip made me ask was ‘how did the macaques know how to synchronously produce these sounds?’. Furthermore do these activities in any way relate to the origins of language? During my observations of lemurs I have observed similar barking sounds and their ancestors have diverged from ours some considerable time earlier at approximately 63 million years ago.
The significance of the barking sound as well as the characteristic snout of the lemur are somewhat reminiscent of the dog and interestingly the dog’s ancestor diverged from our ancestor some 85 million years ago. However the lemurs on Madagascar have very few natural predators and so the purpose of their vocalisations is more likely to relate to territorial displays or conflict between males.
In summary the clips above show evidence of vocalisations within groups being used for purposes that would be consistent with the two main types of selective pressure and it is not unreasonable to suppose that these powerful drivers may well have contributed to the origins of language. In these cases vocalisations produce very clear signals, signals which over time could become more refined through competition.
One of the readers has suggested that the bird in the above footage is a Great Hornbill. While this is not a ‘bird of prey’ or raptor, it is noted that the Great Hornbill preys on small mammals. I have amended the title of the article accordingly, replacing ‘birds of prey’ with ‘predators’ although the central argument in the article remains unchanged. I have included some footage of the Great Hornbill taken in Kerala to provide a comparison with the bird seen in the above footage for the interested reader.
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