Two liger cubs - a cross between a male lion and a female tiger - are being nursed by a dog at a zoo in Weihai, eastern China.Four cubs were born at the Xixiakou Wildlife Zoo earlier this month but only two survived.The mother stopped feeding the cubs after a few days so the dog, which had recently had its own puppies, was enlisted to help.Ligers are extremely rare and are thought to only be born in captivity.Zoo spokesman Cong Wen said it was not clear why the tiger had stopped feeding her cubs, the Associated Press reports.But she said that after some initial problems, the pair were feeding well from their canine stepmother.Although they are a different species, tigers and lions are of the same genus so are able to breed together.Ligers are the largest known cat, usually growing much larger than either parent.Source: BBC