Northwest China, already suffering from desertification, has been training foxes to hunt out rampant rats blamed for destroying grassland and forests.
About 225 captive-bred foxes have been released to the wild in Ningxia Hui and Inner Mongolia autonomous regions and Shaanxi Province over the past four years to curb the fast reproduction of the rodents which eat grass and gnaw tree roots.
Trainers feed rats to young foxes in captivity to improve their hunting techniques. As they grow, they are taken to pastureland regularly to adapt to the natural environment.
The foxes have been doing well in the wild, reducing the number of rats by up to 95.7 percent in a mountainous region of Haiyuan County in Ningxia between 2003 and 2004, said Li Kechang, deputy director of Grassland Division of the Ningxia Agriculture and Animal Husbandry Department.
They also mastered the skills to burrow and some silver-black foxes freed from 2003 to 2005 have mated with wild red foxes.
Foxes are ideal rat-catchers, and are cheaper than poisons, which the rats can adapt to and which endanger other animals, said Li.
Rats have thrived in Northwest China, partly due to global warming, some experts said. Efforts to develop farmland to grassland and forests also provide favorable living conditions for them. However, their natural enemies, such as foxes and weasels, are gradually disappearing due to human activities.
Other provinces, including Gansu and Qinghai, were also using the approach to eradicate rats, which were threatening more than 100 million hectares of sapling forests across the country, said You Dekang, the State Forestry Administration's head of plant diseases and insect control.
In addition, experts in Ningxia's Guyuan City have started to "recruit" weasels in the "ratcatcher force" this year.
"It is hard to monitor foxes' activities and the number of rats, so we are deploying weasels, who also prey on rats, to ensure the effect," said An Yongping, an official with the county's forestry bureau.
Workers had captured young wild weasels and were trying to breed them. They would go to the worst-plagued areas to restore the ecological balance, said An.
Moreover, the far western region of Xinjiang Uygur Autonomous Region is preparing to raise starlings in artificial nests to create an "air force" of birds to catch locusts, which destroy more than three million hectares of pasture every year.
Local officials believe that using starlings is the best biological means to control locusts, as previous means, such as chickens, had proved inadequate and spraying pesticide had contaminated pasture lands, home to millions of herdsmen.