Two purebred Siberian tigers of German pedigree recently fathered nine mixed-blood cubs at the world's largest Siberian tiger breeding center in northeast China's Heilongjiang Province.

The purebred tigers of German origin were among six imported to the Hengdaohezi tiger breeding center in 2000 and 2001 to improve the genetic quality of the local group and prevent their inbreeding and the subsequent genetic degradation, said Liu Dan, general engineer of the base.

Mothers of the nine cubs were both purebred Siberian tigers of Chinese origin and it was the first time for them to have offspring with an exotic spouse, Liu said.

"The baby tigers are all healthy and lively, and their mothers are caring enough to provide adequate nutrition for them all," he added.

Liu said the base planned to submit relevant data of the nine tiger cubs to an authorized British organization to authenticate their pedigree, which may not follow their German fathers or Chinese mothers entirely.

Founded in 1986, the Hengdaohezi center is home to some 300 Siberian tigers bred in captivity.

But Liu and his colleagues have noticed signs of degeneration in the tigers, including slow physical development, blurry stripes, deformity and underdevelopment of organs.

"The inbreeding coefficient is now at a dangerous level inside the center," he said, adding that it would be more likely for mass degeneration to happen if the tracking of the species' genes was not done.

To keep track of their bloodlines and avoid inbreeding, they have joined hands with the Chinese Academy of Forestry Sciences in launching a DNA pedigrees and genetic management system to test and register the DNA of Siberian tigers.

But Liu said it was difficult for zoologists at the center to find the biological father for tiger cubs when they came to register their pedigree since a female tiger usually mated with several other male tigers in the past.

To address this problem, the program would first analyze the genes of those tigers and establish pedigree files according to their DNA.

"We would then choose the best candidate female tigers for a given male tiger, according to our analysis of their genetic data with software, to produce offspring with the lowest inbreeding coefficient," said Wang Ligang, an official working in the center.

"It is important to keep the species pure to guarantee a sound reproduction of the population," said Zhang Wei, deputy director of the wildlife testing center with the State Administration of Forestry.

"Otherwise, genetic degeneration would bring down the quality of the species and make it more difficult to survive," he said.

The Siberian tiger is among the world's 10 most endangered species, with only less than 300 living in the wild, mostly in Russia's far east. Fewer than 10 Siberian tigers are now believed to live in the wild in China's northeast.

Officials at the center estimate that the number of bred-in-captivity Siberian tigers there will rise to 500 by 2005 and on that basis the figure will double by 2010.

(Xinhua News Agency May 25, 2004)