Praveen Karanth, the IISc professor who led the study
New Delhi, Aug. 28: India’s ubiquitous Hanuman langurs found everywhere, from the eastern coast to the Rajasthan desert and the Western Ghats to the Himalayan forests, are actually at least three species of monkeys and not one species as mislabelled for decades.
Biologists at the Indian Institute of Science (IISc), Bangalore, have used a combination of genetic, ecological and body trait studies to cluster Hanuman langurs into three species, but suspect there are at least two more — in the Himalayas and Kashmir.
Their findings vindicate the claims of British primatologist William Charles Osman Hill who, after studying monkeys in the jungles of Sri Lanka, had suggested 75 years ago that Hanuman langurs comprise multiple species. But zoologists who followed him had dismissed his ideas.
“What we thought of as a single monkey turns out to be at least three distinct monkeys, perhaps more,” said Praveen Karanth, associate professor at the Centre for Ecological Studies at the IISc, who’s been studying Hanuman langurs for nearly 15 years.
Karanth and his colleagues, who conducted genetic studies on hair, tissue and faecal samples from 130 Hanuman langurs from wild and captive populations across the country in their latest study, have just published their findings in the journal Conservation Biology.
The Hanuman langur is regarded as a sacred monkey, primatologists say, possibly because its long tail and dark face are consistent with the tale of Hanuman burning Ravan’s Lanka.
The new study’s results have implications for conservation. What was once seen as a large population of a common monkey found across the country, scientists say, should now be regarded as populations of three species — Semnopithecus entellus, Semnopithecus hypoleucos and Semnopithecus priam — that live in their own ecological niches.
Entellus is widespread and is viewed as capable of living in human-modified environments, but priam and hypoleucos are largely confined to forested areas and thus face a greater threat.
The International Union for Conservation of Nature has placed the Hanuman langur in the “least concern” category. At the IISc, research scholars C.N. Ashalakshmi and Chetan Nag led by Karanth used sets of genes as markers and found the Hanuman langurs could be clustered together into three distinct groups on the basis of the markers.
Earlier studies by zoologists had already identified differences in body traits and ecological niches.
Hill, the British primatologist, had in 1939 observed museum specimens and forest monkeys in Sri Lanka and proposed that the Hanuman langurs — distinguished by their dark faces — should be viewed as multiple species. But in subsequent decades, other zoologists challenged that idea and classified Hanuman langurs into sub-species to explain their body trait differences and diverse habitats.
“These genetic studies confirm what many of us have long suspected,” said Mewa Singh, a primatologist at the University of Mysore in Karnataka who has been observing Hanuman langurs for nearly 40 years. “The differences in their body traits are subtle but significant.”
Entellus, for instance, has a tail carriage that loops towards the monkey’s head, while the tail carriage of hypoleucos loops backwards towards the ground. Priam’s tail moves away from the head but doesn’t drop down as much as in hypoleucos.
The extent of blackness on the hands also differs in each species. The data from such body traits, genetics and behavioural features justify treating the Hanuman langurs as distinct species, Christian Roos, a senior scientist at the German Primate Centre in Gottingen, Germany, told The Telegraph.
Singh and others believe that the Hanuman langur in the Himalayas should also be treated as a distinct species.
“The big Hanuman langur is 100 per cent different in size, colour and body proportions, from those from the plains and lowlands,” said Colin Groves, a primatologist at the Australian National University, Canberra, who has studied monkeys in India.
“There is another species of Hanuman langur restricted in a single place in the Kashmir Valley and is one of the most endangered species of primates,” Groves said.
But some scientists point out that genetic studies on a larger number of samples would be necessary to upgrade Hanuman langurs from sub-species into species.
“The differences we’ve observed could be attributed to the adaptation to local ecological habitats,” said Anil Kumar Chhangani, a primatologist at the Maharaj Ganga Singh University, Bikaner, Rajasthan. “Humans who live in different parts of the world also look different.” But Groves said the concept of sub-species is “slippery” and most taxonomists would today refuse to recognise sub-species.
The hair, tissue and faecal samples used by the IISc team for their genetic studies came from parts of Bengal, Gujarat, Andhra Pradesh, Karnataka, Uttar Pradesh and Rajasthan.
“Taxonomists, especially those working with primates, believe that the best way to recognise a separate species is to find whether the populations in question are consistently 100 per cent different in some heritable character or characters from all such populations — this is certainly the case with (Hanuman) langurs.”