Image copyright VAN ROEUN Image caption Rice field rats are considered a delicacy in Cambodia

A unique harvest is under way in the rice fields of Cambodia where tens of thousands of wild rats are being trapped alive each day to feed a growing export market for the meat of rural rodents.

Popularly considered a disease-carrying nuisance in many societies, the rice field rats, Rattus argentiventer, of this small South-East Asian nation are considered a healthy delicacy due to their free-range lifestyle and largely organic diet.

Rat-catching season reaches its height after the rice harvest in June and July when rats have little to eat in this part of rural Kompong Cham province, some 60km from the capital Phnom Penh.

That lack of food coincides with seasonal rains that force the rodents onto higher ground, and into the 120 rat traps local farmer Chhoeun Chhim, 37, said he set each evening.

"Wild rats are very different. They eat different food," said Mr Chhim, explaining with a gourmand's intensity the difference between rice-field rats and their urban cousins, which he considers vermin unfit for the cooking pot.

Common rats "are dirty and they have a lot of scabies on their skin," Mr Chhim said. "That's why we don't catch them."

Somewhat proudly he listed off the superior eating habits of the rats he had caught the night before: rice stalks, the vegetable crops of unlucky local farmers, and the roots of wild plants.

'Tastes like pork'

On a good night, he can catch up to 25kg of rats.

"After the harvest season the rats don't have much food to eat, so it is a good time to catch them," he said, unloading his motorcycle of several large, steel cages filled with rats at the home of the local rat trader.

Though rat meat tastes "a bit like pork," Mr Chhim said it was not really his preferred meal.

"We sell the rats for money and buy fish instead," said Chin Chon, 36, another rat catcher as he dropped off several more packed cages to be weighed, graded and repacked for export.

Image copyright VAN ROEUN Image caption Cambodian rat catcher Chhoeun Chhim sells his harvests to a local dealer

Image copyright Van Roeun Image caption Some of the rat harvests are sold to traders from Vietnam

All of their catch, which amounted to 200kg of noisy, squealing rats on a recent morning, is exported exclusively to Vietnam.

Rat meat can be grilled, fried, boiled in a soup or minced up in a pate, said Chheng An, 22, as he prepared his motorcycle for the four-hour journey over bumpy, dusty roads to deliver the day's batch to a rat trading post at the Vietnamese border.

"It's a good meat. It can be cooked many ways. Rats are very expensive in Vietnam and very cheap here," he said. He wobbled away on his motorcycle as it struggled under the weight of his teeming cargo.

Booming business

At the height of the rat-catching season, rat trader Saing Sambou, 46, exports up to two tonnes of rats each morning to Vietnam.

In the last 15 years, her business has grown almost tenfold. Rat meat initially sold for less than 20 cents per kg, now she earns $2.50 per kg, and demand for rat meat increases each year.

Like most Cambodians, Mrs Sambou does not commonly eat rat, though she has become a great believer in the meat, which she say is 100% safe for human consumption.

Gesturing to some scrawny specimens of farmyard poultry pecking in the dirt at her feet, Mrs Sambou explained: "I think rats are cleaner than chickens or ducks.

"Rats eat only roots and rice."

Sporting a recent rat bite on his finger, her nine-year-old son, Roeun Chan Mean, likes to steal a snack from his mother's stock every once in awhile.

"Rat liver and thigh are the most delicious," Chan Mean said, while his two pet dogs made their own quick breakfast of a pair of rats who had attempted to escape during the morning export packing process.

Hean Vanhorn, a department chief at the Ministry of Agriculture in Phnom Penh, said the rat meat trade was also helping to protect the country's rice crop.

"Hunting rats for food and sale contributes to preventing damage to rice," he said.

Image copyright VAN ROEUN Image caption Vietnamese rat traders head to the border with Cambodia to buy rats

Image copyright VAN ROEUN Image caption Some traders skin and prepare the rat meat before selling it on

At the Cambodia-Vietnam border crossing in Koh Thom district, Thuong Tuan, 30, sat beneath a tin roof in the morning heat and overpowering stench of rodent odour, efficiently chopping and skinning a batch of large, dark-grey rats.

Reaching into a deep cage, her young helper, Minh, 13, grabbed rat after rat by fleshy tails and, in a fast, swirling wrist-action, dispatched each one against a large rock.

Customers in the nearby Vietnamese town like to buy her biggest rats fresh and ready-to-eat, said Ms Tuan, who is Vietnamese and runs the largest rat-trading operation at this border gate.

"People come from far and wide to buy. They like the big fat ones," she said, comparing her own substantial calf muscle to the size of the rats her Vietnamese customers prefer to buy.

And, of course, Ms Tuan reminded me: "It's more delicious than pork."