Bluff in Zoo

In Bluff im Zoo, the players are returning from the zoo and talking about who's seen the biggest and most animals — but not everyone is telling the truth. On a turn, a player can do one of the following:

 Play a card face down on a pile in the middle of all players and claim to have seen a certain number of one of five kinds of animal; this number must be either higher than any previously claimed number or the same number of a larger animal.
 Not play a card and make a claim.
 Doubt the previous player's claim.

When a player doubts an opponent, all cards are revealed. If there are at least the number of animals that the previous player claimed, the doubter takes all the cards (which are worth negative points); if not, the person who made the claim collects them. But beware as the deck contains special cards — e.g., jokers that count as any animal and cards that reduce the number of animals seen — so no one can ever be sure which animals await.

The first player to collect thirty cards loses and ends the game, then the player with the fewest cards wins.