If paper money and coins are considered as cash for humans, what is considered as cash to animals?

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 fish (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 fruit and the penguins fish. So maybe the lemurs use fruit.

FIIIIIIIIIIIIIIIIIIIIISH!!!

Or...

MAAAAAAAAAAAAAAAAAAAAAAAAANGOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!

E.g. '*groan* This ain't worth a two mango minimum!' - Maurice.

Depends on the animal, I guess. The penguins love 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).