Often in English, we use animal idioms to describe a person or a situation. This may be comparing a person’s actions with that of a particular animal or the animal’s behaviour. For example, describing someone who is irritable or angry, you might say, ‘He’s like a bear with a sore head’. If you can visualise how the bear would behave in that situation, you can have an idea of how the person is behaving.
Another example may be, ‘Don’t mention that subject to her. It’s like showing a red rag to a bull‘.
If we want to save money for a special occasion, we say we’re ‘saving money for a rainy day’. Sometimes, if someone wants to save money or keep something without others knowing, we say they ‘squirrel it away’. In this case, ‘squirrel’ is being used as a verb.