The zoo said it treated the birthday boy Monday to a 150-pound cake made of ice, apples, carrots and bamboo with honey and yam frosting on the top. Yun Zi pushed over a number atop the cake to symbolize blowing out the non-existent candles.
Yun Zi's enclosure was decorated Monday with gift boxes full of Bermuda grass and biscuits as well as a cardboard panda and turtle.
Zookeepers said visitors greeted Yun Zi wearing panda hats and T-shirts bearing his image.
Yun Zi's birthday came only one week after that of his baby brother, also a resident of the zoo.