Here is a list of animal idioms
To be a chicken / to be chicken livered
To be a chicken is to be a coward.
- Peter is such a chicken. He is afraid of being alone.
To be like a dog with two tails
Used to refer to a person who seems to be quite happy
- When he discovered that he’d won the jackpot, he was like a dog with two tails.
Gone to the dogs
When a business or a country goes to the dogs it becomes less successful or less prosperous than it was.
- If anarchy prevails, the country will go to the dogs.
Like a fish out of water
If you are like a fish out of water, you are uncomfortable.
- She looked like a fish out of water, when she met her ex-boyfriend at the party.
Something is fishy
If something is fishy, it looks suspicious.
- There was something fishy in the way he behaved at the party.
To be a fly on the wall
Used to mean that you would like to be somewhere secretly so that you overhear everything
- I would love to have been a fly on the wall when they discussed their secret plans.
To be as sly as a fox / a sly old fox
When you are as sly as a fox, you are very cunning.
- My boss is a sly old fox. He knows how to get around the tax laws.