Signs of happiness in guinea pigs:

1. They make gurgling noises mixed with high-pitched humming sounds. At this time, the guinea pig is in a good mood, just like humans humming a song to express their joy.

2. When a guinea pig is happy, its appetite increases greatly and it consumes food and water very quickly. The owner should feed it more food.

3. When a guinea pig is happy, it will climb onto the palm of its owner's hand, fold its ears down, and circle in the palm of its owner's hand.

4. When a guinea pig is happy, it will jump around, run and jump, and shake its head. When it is happy, its ears will turn red.

5. When guinea pigs are happy, they will stare at their owners with their eyes wide open, and may even scream, making them very active.