WARSAW, Oct 29 (Reuters) - A rare white-cheeked gibbon named Dao has been born in a zoo in the Polish city of Wroclaw, moving the critically endangered species a small step further away from extinction. There are only 150-160 such gibbons left in the wild, as well as about 200 in captivity worldwide, Wroclaw Zoo said. In the wild, the animals are found in Vietnam and Laos. They have also been seen in China, although not for 30 years. White-cheeked gibbons are difficult to breed. Dao was born in late September, but the zoo only announced his birth on Thursday. Radoslaw Ratajszczak, the director of Wroclaw Zoo, said it one of the best enclosures for gibbons in Europe, with many trees and ropes. "They can behave naturally here and have peace and quiet. They return the favour with beautiful singing and offspring."