Monkeys at Bandipur show begging behaviour

The juveniles among the wild bonnet monkeys in Bandipur National Park have learnt to beg – a quintessential human behaviour.

Bengaluru’s biologists who report this unique behavioural trait, claim this is the world’s only example of intentional communication shown by wild monkeys.

It's not that all of them display such a behaviour. The adults stick to their known practice of snatching food from the tourist, scaring them most of the times.

But the younger lot, mostly 2-4 years of age, display different behaviour. They give a soft coo-call to establish contact with the human and subsequently extend their hand, begging for the food, when a visual contact is established.

The untrained monkeys also orient themselves within the line of sight of unknown human beings and carefully watch them till the end to see whether food is offered. All of these, scientists say, signal intentional communication. The researchers at National Institute of Advanced Studies documented the new simian behaviours after observing two groups of bonnet macaques, comprising 60 and 32 individuals respectively, from December 2014 to March 2015 at the park.

“Such gestures were seen only among Chimpanzee and Orangutan and mostly in captive conditions,” NIAS professor Anindya Sinha, who led the research work, told DH.

A total of 140 food-requesting events were recorded over a period of 78 days out of which 86 were chosen for the final analyses. In addition, 48 specially designed trials involving four human volunteers and on four subject macaques were conducted.

Sinha and his colleagues Adwait Deshpande and Shreejata Gupta observed four distinct behaviours — monkeys give the coo call and follow it up with the hand-extension gesture. While the purpose of the coo-call is debatable -- it could either to seek attention or to establish the contact – other three traits denotes a clear intention to communicate for food.

The hand-extension behaviour was displayed by the macaques only when there was a mutual visual-attention state established with the human recipient. Other criteria of intentional communication such as moving into the line of vision of the humans were also fulfilled.

“Food requesting by the bonnet macaques thus appears to be potentially an intentionally produced behavioural strategy. All its behavioural components except coo-calls conform to multiple criteria of intentionality,” scientists reported in a recent issue of the journal Scientific Reports. The researchers ruled out the new behaviour being a mere response to the stimuli of food presence.

They showed simple sight of food items, available naturally or held by an individual, neither elicited a coo call nor a hand-extension gesture in any situation. “It is entirely possible that, initially, certain individuals could have acquired the hand-extension gesture from simply reaching out with their forelimbs for the food held by humans. This behavioural act could have then become ritualised through frequent interactions with humans and may have been reinforced when positively rewarded and then spread by social learning mechanisms,” the scientists reported.