A Siberian tiger cub plays with its mother at the Siberian Tiger Park in Northeast China's Heilongjiang province, May 6, 2015. A total of 20 Siberian tiger cubs, one of the world's most endangered animals, were born in 2015 at the tiger park. China established the Siberian Tiger Park in 1986 with only eight Siberian tigers. Currently, there are more than 1,000 Siberian tigers at the park, all of which have undergone DNA tests to prevent "intermarriage" among them.[Photo/Xinhua]