The mountains of Beijing have been crawling with new critters in recent weeks, and locals aren't happy about the new additions to the food chain.

According to a report in the Beijing Evening News on Monday, more than 300 foxes and raccoon dogs were released in Beijing's Huairou District without authorization. The captive animals were reportedly set free by Buddhists as a way of showing benevolence and earning merit.

Releasing animals into the wild has a long history in China, dating back to the Han Dynasty (206 BC-AD 220). The practice is thought to cultivate kindness, compassion and benevolence, but it did not become popular until Buddhism was introduced to China.

The tradition has caused controversy in recent years after guinea pigs and venomous snakes have been released into the wild, causing public panic.

Peng Yuchun, a villager in Huairou's Tanghekou Township, said the animals have attacked chickens, attracting complaints from locals.

"Hundreds of foxes were released into the mountains a few days ago and they killed some of my chickens," Peng told Huairou's forestry bureau.

A witness who saw the animals being released said several people drove to the town on March 27 and "released a bunch of foxes."

Foxes and raccoon dogs

The local forestry bureau said that all the freed animals were arctic foxes, which are not a protected species in China. The foxes and raccoon dogs were all raised in captivity, according to the bureau.

Bureau staff said they have retrieved more than 100 foxes, many of them already dead, presumably from starvation as the animals were not equipped to survive in the wild.

Local police have launched a manhunt for those who released the animals.

A similar incident was reported last week in east China's Anhui Province, after more than 100 foxes were freed in a village in Huangshan City. Investigators found that those responsible brought more than 100 foxes from a farm in Shandong Province and freed them with the help of a local monk. Local authorities have so far retrieved 120 foxes, eight of them dead.

The recent cases have fueled an online debate, with netizens remaining divided on the issue. While many argue that practice conforms with Buddhist beliefs, others say it disturbs the ecological balance and harms society.

According to Chinese law, freeing wild animals must be authorized, and the environment must be suitable for the animals' survival.

Raised domestically

An underground market has emerged to meet the demand.

Kong Lingshui, a law enforcement officer with the Beijing Bureau of Landscape and Forestry, said most of the freed animals were raised domestically. The releasers did not even know where the animals came from, according to Kong, nor did they know if the animals could adapt to their new environment.

"Freeing wild animals blindly disturbs local ecological systems," he said. "We once caught a group of people freeing Brazilian tortoises in Beijing. The animals eat fish fry in rivers and multiply easily, damaging the aquatic ecosystem."

The rewards for the practice are not just spiritual. According to Kong, his team found an animal-freeing organization in 2007 was demanding 500 yuan (US$77) in "releasing fees" and 30 yuan for transportation costs from 500 participants.

"The actual cost of the activity was only 20,000 yuan," Kong said. "Additionally, the pheasants they released barely had any feathers, meaning they could not survive in the wild," Kong added that many released animals, such as sparrows, are recaptured and sold to releasers again." Almost 30 percent of sparrows die in the process."

Chen Junfeng, an officer with the Huangshan forestry police, said the released animals could also threaten other wild species already facing extinction.

There is currently no law to address the release of captive animals, so even if police find the releasers in the Beijing case, it will be difficult to penalize them, said Kong.

Yang Zhaoxia, an ecology expert with the Beijing Forestry University, said China must adopt legislation to encourage "harmonious coexistence between animals, the environment and human beings."