It’s not quite the Mahabharata but two gangs of cousins are enmeshed in a life-and-death battle a few hundred miles south of Kurukshetra, in the storied badlands of Chambal.

Instead of bows and arrows or their modern equivalents – guns and bombs – the war is being fought with lashing tails and razor teeth.

India’s 48-year-old conservation initiative to protect the gharial, a critically endangered, long-snouted freshwater crocodilian species, has encountered an unexpected threat in Chambal. Muggers, a cousin species, are competing for resources with, attacking and even eating gharials.

Wildlife biologists working at the National Chambal Sanctuary, a 610km segment of the Chambal river and a key site for gharial conservation, have documented an increase in the mugger population that they say poses “a serious threat” to the gharials.

The Chambal Sanctuary is a tri-state area managed by Madhya Pradesh, Rajasthan and Uttar Pradesh.

The gharial was once distributed across the subcontinent, featuring in the Indus, Ganga, Brahmaputra and Mahanadi and their tributaries. But habitat destruction from irrigation canals, dams and riverside agriculture and livestock grazing, as well as prey loss from fishing, caused their populations to plummet.

From an inferred 5,000 to 10,000 individuals in the 1940s, their numbers had fallen to under 200 by the mid-1970s.

Conservation efforts — such as protecting habitats and collecting gharial eggs and rearing the young in captivity before releasing them into the river after they reach a size of 1.2m — have helped increase the gharial population. From an estimated 107 gharials in 1979, their population had risen to 2,176 in the Chambal Sanctuary by 2021.

Given that muggers and gharials share freshwater habitats and compete for resources, the gharial conservation programme discouraged any management or intentional release of muggers into sanctuary areas earmarked for gharials.

But a study by scientists at the Wildlife Institute of India (WII), Dehradun, has found that the mugger population in the Chambal Sanctuary has surged from 19 in 1984 to 674 by 2019. The scientists have attributed this increase to the sanctuary’s protected status — curbs on fishing and sand-mining — and
the muggers’ resilience.

“Muggers have become unintended beneficiaries of the gharial conservation programme and are now threatening the gharials themselves,” Surya Prasad Sharma, a WII researcher and lead author of the study, told The Telegraph.

The study, just published in the journal Scientific Reports, was supervised by WII scientists Syed Ainul Hussain and Ruchi Badola. The other co-authors are Mirza Ghazanfarullah Ghazi and Suyash Katdare.

Alongside the mugger population increase, Sharma and his colleagues have documented fights between gharials and muggers, and of muggers eating juvenile gharials. “In size, gharials are comparable or larger than muggers, but muggers are more agile and are likely to win bouts of aggression,” Sharma said.

The study has found higher genetic diversity among the mugger population in the Chambal compared with the gharials. The higher the genetic diversity, the more sustainable the population.

The findings point to a successful colonisation of the Chambal Sanctuary by muggers even though their conservation had not been taken up.