The danger to the world's largest tiger population was underlined when four tigers, two of them cubs, were found poisoned on the outskirts of Dudwa National Park in northern India on New Year's Day.

Another two tigers were killed in the same way in December in the Jim Corbett National Park. In another incident in December, in the state of Karnataka, a tiger was blown to pieces after eating meat which contained an explosive.

Local sources in Uttar Pradesh, the state where the Dudwa park is located, blamed the latest incident on the chronic problem of habitat. With its vast and ever-increasing human population, India offers the wide-ranging tiger an ever-shrinking terrain in which to hunt.

When the Dudwa National Park was established 30 years ago, a buffer zone of forest separated fields of sugar cane belonging to local farming communities from the reserve. But with the pressing demand for firewood and more land for cultivation and pasture, that buffer has gone. Tigers fan out from the reserve into the farmland, where the farmer's cattle make easy prey.

The tigers and their cubs even sleep out amid the sugar cane. Last year a local man who surprised one napping tiger family was killed.

According to this explanation, farmers fed up with the loss of their cattle and panicked by the menace posed by the cats to their families smeared poison on the carcass of a calf and left it in the fields where the tigers were often seen. The cats took the bait and died.

But Amanda Bright, chairman of the trustess of the Global Tiger Patrol, points to a more sinister explanation. The poisoned tigers, she says, were probably among the 300-plus killed each year in India by poachers.

The poachers sell the skins, bones and body parts for use in Oriental medicine. These find their way to places such as Badar Market in Old Delhi and from there via Ladakh, Kashmir or Kathmandu to pharmacies and specialist restaurants in the Far East.

Japan, she says, is the worst offender. Tiger stew and tiger penis soup are among the preparations favoured by the wealthy. Both cost several hundred dollars a portion.

Poaching and habitat encroachment are not the only threats to India's tigers. Tourists are another menace.

In the central state of Madhya Pradesh, radio collars which were attached to tigers to monitor their movements were subsequently used to track the animals and organise "tiger shows" for visitors who otherwise would be unlikely to glimpse the shy cats.

Earlier, such shows were organised by cornering a park's tigers with elephants.

The practice was banned in 1994, but according to one report, the ban exists only on paper and shows of this sort have been staged all over the country.

It is yet another human encroachment on the tigers' preserve. But such practices are overshadowed by the poaching.

"It started in India in 1991, when the Far East ran out of their own tigers," says Ms Bright.

Global Tiger Patrol last year spent 3,2-million equipping Indian reserves with jeeps, boats and motorcycles for the fight against poachers because, as she says, with a few thousand big cats, "India is the country with the largest population of tigers and the best chance of holding onto it." But it will also soon be the country with the largest human population. Many are excruciatingly poor and seeling tiger parts remains a highly lucrative trade.