At least a dozen rhinos have been poached in Kaziranga in the first six months of this year. (AFP Photo)
As night falls over the lush plains of Assam's Kaziranga national park, a small group of lightly armed forest guards sets out on foot to protect the world's largest population of one-horned rhinos.
These men with their ageing rifles and small plastic torches are on the front line of the battle against increasingly sophisticated international poaching networks that prey on the rare animals, entering the park under cover of darkness to kill them for their horns.
At least a dozen rhinos have been poached in Kaziranga in the first six months of this year, more than twice the number killed in the whole of 2006.
A decade ago, India had all but declared victory over poaching in Kaziranga, a 166-square-mile protected area of forest that is home to around 2,500 rhinos.
But recent years have seen an alarming upsurge in the slaughter of the animals, whose horn is highly prized in neighbouring China and in Vietnam.
"The poaching network has become more systematic, stronger, more efficient," said Amit Sharma, senior coordinator for rhino conservation at WWF India, who blames a surge in demand that has seen prices top $100,000 per kilo for the final product.
Park rangers say they are woefully under-equipped to deal with the modern, sophisticated weapons used by the poachers, including AK-47s and night-vision goggles.
Many of the myriad insurgent groups operating in the northeast are involved in the trade, which passes through the neighbouring state of Nagaland into Myanmar before being smuggled to China.
The issue is hugely emotive in Assam, where the rhino is both a source of pride and a big tourist draw.
An Indian one-horned rhino grazes in Kaziranga National Park. (AFP Photo)
It hit global headlines in April, when a rhino was poached on the very day that Britain's Prince William and his wife Kate visited the national park.
"Many years ago you would see rhinos everywhere around here," said local villager Damayanti Chhetri. "The poachers have no heart."
Local people are a vital source of information for the park rangers, providing tip-offs about upcoming poaching raids.
But some are also in the pay of the poachers, who rely on their knowledge of the local terrain, according to one senior forest official.
"Locals know every corner of the park. Huge money is involved. It is a risky job, and still they do it," said the official.
The risks are high: Kaziranga's forest guards have the right to shoot suspected poachers on sight, and dozens have been killed over the last decade.
The policy is controversial, but they argue it is justified as no one is allowed to enter the park without permission.
Two years ago Dipen Sawra, a 35-year-old father of two, failed to return home after a forest guard offered him work cutting firewood. He was later found dead with a bullet wound to the head.
"They were good friends, he (the guard) used to come and drink tea with us here," his father Vikari Sawra told AFP at the family's small mud and straw home.
"We never thought something like this would happen," he said.
The family say they never received a death certificate or the results of the post-mortem. The guard was arrested on a murder charge, but was later released, and his case is still pending.
Assam's new forests minister Pramila Rani Brahma told news agency AFP in Guwahati that local poverty was fuelling the trade in rhino horn.
A rescued male rhino calf is fed a bottle of milk at Kaziranga National Park. (AFP Photo)
Last month she suspended Kaziranga's director after he failed to inform her that a rhino had been killed while she visited the park.
A few weeks earlier, police arrested two forest guards on suspicion of covering up poaching after the corpse of a rhino was found buried in the park, its horn removed.
WWF India's Sharma does not believe park authorities are complicit in the trade, but says the pressure they are under may be leading them to cover up incidents of poaching.
To help police secure convictions, WWF India is working with the Assam government to set up a rhino DNA database -- a system already used in South Africa. Traffickers may be identified by evidence left when they handle the horns.
"Every rhino has a fingerprint in form of DNA," said Sharma. "In court it's going to be very easy to convict (with DNA evidence)."
But for him, the priority should be to provide the struggling forest guards with better equipment.
"The backbone on which we are trying to save our rhinos needs to be strengthened," he said.
"They are our footsoldiers, without them we cannot protect our rhinos."