Liu Tong, an expert with the New York-based non-profit organization Wildlife Conservation Society, checks a suspected paw print of siberian tiger in a forest farm of northeast China's Heilongjiang Province, Jan. 10, 2012. (Xinhua/Wang Kai)

Dozens of volunteers braved freezing temperatures and knee-high snow to clear traps for endangered wild Siberian tigers in northeast China this week.

In six groups, 73 volunteers searched six forest farms in the northeastern province of Heilongjiang in a four-day trap-clearing campaign that ended on Jan.13.

The volunteers included members such as doctors, computer engineers, public servants and college students, and among them there was an Australian named Melissa Pettigrew.

Winter is a tough season for the rare tigers as their prey becomes scarce, and the animals sometimes die from not having enough to eat or by coming into contact with a hunter's bullet or a trap.

Wang Lin, an initiator of the trap-clearing campaign, said that every winter, poachers set iron wire ring traps to catch wild animals like rabbits and roe deer as they can be more easily tracked on snow.

"The traps are cheap but very dangerous," said Wang. "They reduce the population of small animals, which are often prey for the tigers. They can even hurt tigers or help to catch them."

In late October 2011, a wild Siberian tiger was found dead with a trap around its neck in the city of Mishan in Heilongjiang, prompting environmentalists to call for enhanced wildlife protection.

Four to six wild Siberian tigers are believed to be living on the six forest farms, underscoring the importance of the volunteers' protection efforts.

Workers at one forest farm filmed a Siberian tiger last November, and with improving ecology, there have been more and more tiger paw prints spotted over the past couple of years.

Siberian tigers are among the world's rarest species. The population of wild Siberian tigers is estimated at around 500, most of which live in Russia's far east and China's northeast.

 In November 2010, leaders from 13 countries, including China and Russia, committed to backing the Global Tiger Recovery Program, which aims to double the number of tigers in the wild by 2022.

China has set up nature reserves along its border with Russia to better protect the tigers' habitats by curbing excessive deforestation and poaching.

"Clearing one trap means reducing some danger," said Liu Tong, an expert with the New York-based non-profit organization Wildlife Conservation Society. "What we want to see most is no poaching and no traps in the habitats of the endangered Siberian tigers."