Harassed by rodents running rampant on vegetation, locals in northwest China's Gansu Province have turned to traditional methods of pest control -- hawks, bows and arrows.

Agricultural authorities in the Gannan Tibetan Autonomous Prefecture have erected tall wooden poles in the nearby pasture for hawks to rest their wings and take better aim, as the birds often detect and catch their prey from elevated positions.

The pasture spans 2.16 million hectares on the eastern end of the Qinghai-Tibet Plateau. About a third of the pasture is harassed by rodents including rats, marmots and moles.

"A rodent can dig a hole 100 cm in diameter within 20 minutes," said Yang Linping, a forestry official in Gannan's Maqu County. "Very soon, large pieces of the pasture will become replaced by their mounds and the damage is often unrepairable."

In addition to rodent-hunting hawks, authorities have also encouraged local residents to take up their traditional weapons, bows and arrows, to fight rats.

Yang Baijia, 41, leads a team of 15 archers in Maqu County. "Each of us can kill at least 50 rodents a day."

The archers have also created a trap which they put in tunnels near new rodent mounds. When the rats run by and touch the device, arrows are shot out in all directions.

These seemingly primitive ways of fighting rodents are environmentally friendly and good for the pasture's ecology, said Liang Haihong, a forestry official in Gannan. "In the past, people used raticide, which put hawks and other animals at risk and harmed the ecology."

Liang said authorities have been working to promote the local people's awareness of environmental protection in recent years.

"Instead of killing all rodents, we tell the locals that rodents play their role in the pasture's ecology and an average of 22 rodents on each hectare would make an ideal biological chain."