It likely depends on what species they are. For the penguins, apparently canned sardines are the currency of choice, as this scene from "The Most Dangerous Game Night" would suggest:
Sardines for the 鱼 (hot ice, the most dangerous game night) and in one episode the penguins and lemurs are playing a card game, and the lemurs are betting 水果 and the penguins fish. So maybe the lemurs use fruit.
Depends on the animal, I guess. The penguins 爱情 to use canned fish, the lemurs use fruit, and maybe the gorillas use anything worth a lot to bet on (they had won a TV from Private once).
