A 13-year-old tigress gave birth to twin female cubs Sunday at the Siberian Tiger Park in Harbin, capital of northeast China's Heilongjiang Province.  

This was the eighth birth for the Siberian tigress nicknamed Big Beauty, who is mother to 24 little tigers.

Zoologist Su Weilin with the park said that it is not easy for a tigress to become pregnant and give birth at the age of 13, which is equal to 50 in human years.

The life expectancy for Siberian tigers is from 20 to 25 years.

Possibly as a result of her senior age, Su said, Big Beauty has failed to produce milk for her two daughters.

So, currently the two cubs, weighing 2.3 kg and 2.5 kg respectively, are under care of zoo workers.

All her other cubs were fed and raised by herself, Su said.