To celebrate, the zoo's executive chef created two birthday cake that were placed inside Maggie's exhibit, which she shares with boyfriend, Brunei, 20.
"They're going to take a peek around the exhibit and probably go straight for the cake," said Amy Coons, senior keeper. "They're made of carrots and sweet potato. About fifty pounds of carrots and ten pounds of sweet potato."
Maggie's birthday gifts included rice, oatmeal and cracked corn.
Maggie was born at San Diego Zoo in 1961 and is the fifth oldest Bornean orangutan in the world.
"I like to equate it to somebody turning a hundred years old. It's definitely possible but not everybody does it and so it's a special occasion when somebody hits a hundred," said Coons about Maggie's age in human years.
