The artist said he was playing with the idea of real and fake, and of nationalist symbolism.
"I don't think even the copies are exactly the same. It's a new understanding of the total project. It's not as if some are cast from the original. It's a new interpretation," he said, in an interview with Alison Klayman, a filmmaker.
"My work is always dealing with real or fake, authenticity, what the value is, and how the value relates to current political and social understandings and misunderstandings. I think there's a strong humorous aspect there. The [Yves Saint-Laurent] zodiac auction [in February 2009] really complicated the issues about art, about the real, about fake, resources, looting, about the appreciation of objects all these kinds of issues," he added.
Mr Ai's heads are oversized, standing 10ft-tall on their pedestals and weighing 800lbs each. However, he said that he wanted the work also to be playful and accessible to the general public.
"I want this to be seen as an object that doesn't have a monumental quality, but rather is a funny piece a piece people can relate to or interpret on many different levels, because everybody has a zodiac connection," he said.
According to Chinese tradition, everyone is born under one of the 12 animal signs of the zodiac, depending on the year of their birth.
Currently, China is celebrating the year of the Rabbit.
Legend has it that the animals of the zodiac were chosen by the Jade Emperor, the ruler of heaven, who according to Taoist mythology invited all creatures to join him for a New Year's Day celebration.
Only 12 showed up, and the years were named in the order they arrived.
The bull would have arrived first, but the rat sat on his back, jumping off just before they arrived. The rabbit came in fourth, hopping on stones to cross a fast-flowing river.