The bonnet monkey, commonly found at temples in South India, is losing its ground. Researchers have observed that the monkey, endemic to peninsular India, is being steadily replaced by the aggressive rhesus monkey from northern parts of the country.

Two research teams led by Mewa Singh of the University of Mysore and HN Kumara of Salim Ali Centre for Ornithology and Natural History, Coimbatore, have been monitoring the population of the bonnet monkey in southern India for 25 years. “Most people tend to think that bonnet macaques are found in abundance, but when we started assessing their numbers in agricultural fields and forests, we found they were declining,” said Kumara.

Although the bonnet monkey has the conservation status of “least concern”, the scientists believe the species may soon become endangered given the incursion of the more dominant rhesus monkey and the resultant loss of habitat.

Aggressive invader

The population of the bonnet monkey, which usually resides in non-forested areas and vegetated roadsides, has declined by around 50% in southern Indian between 2003 and 2015.

“It has also been observed that the rhesus macaque with a larger body size and more aggressive temperament than the bonnet macaque displaced the latter from food and preferred habitats if an encounter occurred between the two species,” the researchers said.

A survey, conducted from 2004 to 2008, of the populations of rhesus and bonnet macaques across various zones in peninsular India found that rhesus macaque had gained ground since 1981, when the previous such study was done. In about 25 years, the rhesus monkey had extended their range by about 3,500 sq km into the traditional habitat of the bonnet monkey.

In 2014 and 2015, Singh and Kumara conducted another survey across various temple and tourists places in southern India, as well as forest areas. They found that, combined with the previous surveys, the rhesus macaque had invaded nearly 28,000 sq km of the bonnet macaque’s habitat in less than four decades.

“We did not find the bonnet monkey in many places they were found earlier,” said Kumara. He explained that with the unceasing movement of the aggressive rhesus macaque to the South, the endemic species was losing its range area. The rhesus macaque is also a fast breeder. “There may not be direct aggression, but once the resource is occupied by another group, the bonnet monkey has to move away,” Kumara said. “In that way, it is a very gradual process.”

Landscape changes

Urbanisation, reduced canopy connectivity and changes in roadside landscape too have contributed to the decline of the bonnet moneky by more than 65% in the past 25 years, the researchers found.

In a case study of roadside habitats spread over 464 km around Mysore, Karnataka, the researchers found that compared to 889 bonnet monkeys seen in 2003, there were only 407 in 2015. The number of their groups had also come down sharply from 42 to 24 in this period. “Many single roads have now been converted into lane roads and the dense vegetation of banyan trees has been replaced by barren lands and urban structures,” Singh told The Hindu, emphasizing that this loss of traditional habitat was also leading to the bonnet monkey’s decline.

Since monkeys are often considered a menace, many are killed or translocated to other areas by forest officials, said Kumara. Of those translocated, many die because of stress or inability to adapt to the changes in habitat or climate.

The researchers have called for devising conservation strategies to prevent the bonnet monkey from getting to the brink of extinction. Noting that populations of the bonnet macaque is still relatively stable in vegetated hillocks with temples, such as Chamundi, they have suggested that such hillocks be turned into conservation reserves for the species.