You cannot play an animal card if you don't have the required enclosure size/type available or cannot pay its cost. The animal card remains in your hand and you must choose a different action or pass your turn.

Action cards can be upgraded through certain game effects, flipping from side I to side II. The upgraded effects take place immediately when you use that action card on future turns.

When your Appeal and Conservation counters meet or pass each other, the game immediately ends. This triggers the final scoring phase where players calculate their final scores using their Final Scoring cards.

Special Enclosures (Reptile House, Large Bird Aviary, Petting Zoo) have specific rules for which animals can be placed in them. They typically provide unique benefits but may have restrictions on animal types or sizes that can be housed there.

If there are no cards left in the Zoo deck to refill the display, you can still use the Cards action to draw from your hand or perform other card-related activities, but you cannot take new cards from an empty display.

Some Sponsor card benefits must be used immediately when played, while others may provide ongoing effects or optional abilities you can use later. Check each card's specific text to determine the timing of its benefits.

Yes, you can build enclosures on bonus spaces on your zoo map. You typically receive the bonus when you build on that space, and the bonus may provide ongoing benefits depending on what's shown on that space.

X-tokens are typically consumed when used and provide specific benefits as described on cards or game effects. You can generally save unused X-tokens between turns unless a specific effect states otherwise.