'One day, wolves may attack humans'

The greatest fear of Bayishi Hule, the herdsman from Mazongshan, is that one day the wolves might attack people if their packs keep growing. "The wolves often come in a pack of six or seven and can kill dozens or even 100 mountain goats at a time," he said.

"They don't eat all of them. They just bite through their throats and leave them bleeding to death like it is a game to them," he said.

Wolves are a protected species in China. Anyone who wants to hunt them must obtain permits from forestry administrations, or they will face criminal charges. As private citizens are forbidden from owning guns in China, herdsmen can only count on police or other armed forces to control the predators' numbers.

In 2010, the Gansu government began to compensate herdsmen who lost their livestock to wolves.

Herdsmen will receive compensation of 20 percent of the market value of their livestock if they are injured by protected species, and 80 percent of the market value if they are killed. If loss of human life is involved in a wolf attack, the victim's family is compensated at 20 times the average annual income of the province's rural population.

Wolf attacks have been widespread. In the Beita Mountains in the Xinjiang Uygur autonomous region, which also borders Mongolia, officers at the Kufu border police station dealt with dozens of such cases in 2012. More than 800 sheep, 80 cattle and 20 horses were killed by wolves, said Res, one of the station officers.

"The ecology on the grassland is getting better now because of the national conservation program - that's why we see a rising number of wild wolves," he said. "Also, we cannot shoot them because they are protected animals and the herdsmen don't have effective methods to keep the wolves away."

Yang Weikang, a researcher at the Chinese Academy of Sciences' Xinjiang Institute of Ecology and Geography, argued that the increasing activity of wolves illustrates the damage done to the grassland's ecological system.

"Livestock have overconsumed the plants on the grassland, which has caused the number of wild rabbits to decrease. As a result, the wolves have to seek an alternative food source, such as herdsmen's livestock," he said.