CHENGDU - Four years after being identified as female at birth, giant panda Pu Pu has actually been found to be male, according to the China Conservation and Research Center for the Giant Panda.

Earlier this month, workers with the center noticed through monitors that Pu Pu, temporarily living in a zoo in the northeastern city of Shenyang, showed behavior commonly associated with male giant pandas, such as moving backward and lifting legs.

The workers immediately informed the zoo, prompting the keeper at the zoo to carefully check his genital area. Everyone finally agreed that Pu Pu was male.

Huang Yan, an expert with the center, said the gender of giant pandas was hard to identify because the genitals of a cub, which weighs a mere 100 grams, were not obvious.

Zoologists once believed that the gender of a giant panda could only be precisely known after they reached three years old.

"Experienced keepers or zoologists rarely mistake the gender of giant pandas today," Huang said. "Even though analysis of sex chromosome can identify the gender of animals, the method is seldom used in rare species."