The Jharkhand forest department has initiated a study to revive the dwindling population of Bison, popularly known as Gaur, at Palamu Tiger Reserve (PTR), an official said.The bovine, a food source for big cats, has already gone extinct from across Jharkhand, excluding the PTR where merely 50-70 bison are surviving, he claimed.According to wildlife experts, poaching, infection and habitat disturbance by local cattle have been the major reasons for the vanishing of bison from Jharkhand."Once Bisons were abundant in Jharkhand's Saranda, Dalma, Hazaribagh, Gumla and some other forests. But, they went extinct from across the state. PTR, mainly Betla range, is the last destination where it is surviving but numbers are on the decline," said former state wildlife board member DS Srivastava.He alleged domestic cattle was posing a major threat to the animal in PTR."Over 1.5 lakh domestic cattle from around the villages in PTR have occupied most of the space of Bison. They are eating food of the Bison and are also spreading several infections such as mouth and foot diseases. The forest department needs to check the cattle grazing," he said.PTR director Kumar Ashutosh said they are carrying out a study to ascertain the parameters that impact the animal."Various aspects are being studied right from their behaviour to survival requirements so that their population could be increased," Ashutosh told PTI.