By Dean Nelson
They have called for a ban on the chemical Carbofuran, which is used as a cheap pesticide by local potato farmers.
Tribal poachers are laying traps for tigers by leaving recently killed animal carcasses filled with the chemical on their territories.
The tigers are believed to die within an hour of eating the carcass and the poachers then sell their lucrative skins, teeth, nails and organs for thousands of pounds to Tibetan and Chinese traders.
Conservationists called on the Indian government to follow the United States, Canada, and Kenya, where it has been banned to protect wildlife.
Officials uncovered the scale of the chemical's use by poachers when they recently interrogated a number of tribals to establish why so many tigers and leopards were being found dead without any obvious cause.
The chemical is transparent and odourless and difficult to detect in tests.
It costs under a pound for enough to kill a tiger but a single grain is enough to kill a bird.
Dr Abhishek Singh of the Endangered Flora and Fauna on Earth Conservation Team said his staff had been tipped off about the use of pesticide while investigating tiger deaths in the Kumaon Hills, the jungle landscape where the legendary tiger hunter Jim Corbett turned pioneered big cat conservation. More....