A television crew filmed a "lost" population of tigers living at a higher altitude than any others known, raising hopes of linking isolated groups of the big cats across Asia, the BBC said Monday.
The cats were spotted roaming in the hills in the remote Himalayan nation of Bhutan by a conservationist and a team from the BBC's Natural History Unit at a height of 4,100 metres (13,450 feet), said the broadcaster on its website.
"Tigers are thought of as jungle creatures and there is pressure on their habitats from all sides. Yet we now know they can live and breed at this altitude which is a safer habitat for them," said tiger expert and conservationist Alan Rabinowitz, who led the expedition.
The team set up hidden cameras wedged into gullies and trees for six weeks to capture the first hard proof that the animals could live at such high altitude, following earlier anecdotal evidence, the BBC said.
The footage shows a male tiger and a female tiger at 4,100 metres and other tigers living at 3,000 metres, it added. Colour footage shows one tiger sniffing the air, while a night shot shows one of the animals prowling.
The female is lactating, suggesting they are breeding, said BBC cameraman Gordon Buchanan, who set up the camera traps that automatically filmed any creature that moved in front of them.
He said he was "convinced that there must now be cubs somewhere on this mountain."
"This is such a significant discovery for tiger survival," he said. "The fact they can live here is just so important, for tigers in the wild, for their future."
Rabinowitz said the discovery would boost an ambitious plan for a "corridor" across Asia in which tiger populations are safe from humans.
"Bhutan was the missing link in this tiger corridor," he said.
Conservation group WWF says numbers of tigers have plunged to fewer than 3,200 from 100,000 over the past century.
Thirteen "tiger-range" countries are to meet in Saint Petersburg, Russia, in November to discuss plans to double the number of wild tigers by 2022.
Explore further: Flocks of starlings ride the wave to escape