Science does not see this relationship in terms of black-and-white
A Hanuman langur (left) and a rhesus macaque (right). Collage by Ajit Bajaj / CSE. Photos from iStock The New Delhi Municipal Council (NDMC) has put up cut outs of hanuman langurs (Semnopithecus entellus) to deter rhesus macaques (Macaca mulatta), ahead of the G20 Summit in the national capital next week, according to media reports.
It has also “deployed ‘30 to 40 people’ to make monkey sounds to create the impression that the animals are alive”, British newspaper The Guardian reported.
But is there any scientific basis to the claim that langurs can fend off rhesus macaques? Even more importantly, should such steps be undertaken?
“It is a most non-scientific action. This is against the Wild Life (Protection) Act, 1972. It is also against our culture and ethos,” veteran primatologist, Iqbal Malik, told Down To Earth (DTE).
She added that the relationship between the two primate species was not necessarily adversarial.
“The best example of this can be seen in the Galta ji Temple near Jaipur. You can see both langurs and rhesus there. In my own field research area, I was amazed to find that langurs and rhesus groomed each other. Just because langurs are black-faced, bigger in size and have longer tails does not mean they are intimidating to rhesus,” she added.
A 2012 paper An instance of inter species interaction between Hanuman Langur (Semnopithecus entellus) and Rhesus Macaque (Macaca mulatta) by Ashish Nerlekar makes observations which are broadly in sync with what Malik said.
The paper noted:
When feeding in their natural habitat, hanuman langur troops do not object to the presence of a troop of rhesus macaques in the proximity, but go their separate way at dusk (Prater 2005).
Nerlekar also described the case after which his paper was titled. On March 29, 2011, he observed a troop of hanuman langurs foraging on the freshly fallen flowers of Butea monosperma and Madhuca indica trees at 6.30 am:
Two langurs, one of which was a female and other of unknown sex were sitting and feeding a short distance away from the troop. Further, a rhesus macaque juvenile was seen socialising and playing with the adult hanuman langur female.
The interaction, according to Nerlekar, happened with the rhesus juvenile “jumping and climbing on the back, and playing as well as feeding along with the adult langur”.
Nerlekar noted in his paper that B Ram Manohar & Reena Mathur (1990) had “described significant play behaviour between infants and juveniles of rhesus macaque and hanuman langur while feeding in a human modified habitat”.
These interactions ranged from play initiation and somersaulting to chase and touch in an area where troops of both the species are fed by pilgrims, Nerlekar quoted the authors as having noted.
Wildlife biologist Faiyaz Khudsar told DTE that the ‘foraging guild’ of both, langurs and macaques was very close in the wild.
“Langurs feed on foliage while macaques feed on fruit and foliage. Both species live peacably enough in the wild and such conflict management is not needed there. What we are seeing in Delhi is an unscientific way of conflict management. A trained langur may fend off a rhesus troop but only temporarily. The major issue is not allowing feeding of wildlife such as rhesus. Until that is taken care of, such stop gap arrangements will not be enough,” he said.
Clearly, langurs and rhesus are not bloodthirsty enemies as we have been led to believe.
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