Idioms about animals

Animals

act as a guinea pig

- to allow some kind of test to be performed on someone
I was not happy to act as a guinea pig for the new training material.

ahead of the pack

- to be more successful than other people who are doing the same thing as you (a pack is a group of animals like dogs or wolves who live together)
The girl studied hard all summer and was ahead of the pack when she returned to school in the autumn.

alley cat

- a stray cat
I began to feed the alley cat and now it comes to my house every day.

as awkward as a cow on roller skates

- very awkward
The little girl was as awkward as a cow on roller skates when she first began riding her bicycle.

as blind as a bat

- blind
The man is as blind as a bat and cannot see more than a small distance ahead.

as busy as a beaver

- very busy
I have been as busy as a beaver all morning.

as clean as a hound's tooth

- very clean
The classroom was as clean as a hound's tooth when the students finished cleaning it.

as conceited as a barber's cat

- very conceited, vain
My friend became as conceited as a barber's cat after she won the award at school.

as crooked as a dog's hind leg

- dishonest
The politician is as crooked as a dog's hind leg and nobody trusts him.

as drunk as a skunk

- very drunk
The man was as drunk as a skunk when he walked into the restaurant.

as fat as a pig

- very fat
The woman in the supermarket was as fat as a pig.

as gentle as a lamb

- very gentle
The girl is as gentle as a lamb when she is with her little sister.

as gruff as a bear

- gruff, unsociable
Our neighbor is as gruff as a bear when we meet him in the morning.

as hungry as a bear

- very hungry
I was as hungry as a bear when I arrived home from work.

as innocent as a lamb

- having no guilt, naive
The little girl is as innocent as a lamb and everybody loves her.

as meek as a lamb

- quiet, docile, meek
The secretary was as meek as a lamb when she went to ask her boss for a salary increase.

as nervous as a cat

- very nervous
The man was as nervous as a cat when he talked to the woman.

as poor as a church mouse

- very poor
My cousin is as poor as a church mouse and never has any money to spend.

as quiet as a mouse

- very quiet, shy
I was as quiet as a mouse when I left my house early this morning.

as scared as a rabbit

- very scared
I was as scared as a rabbit when I entered the empty room.

as sick as a dog

- very sick
My friend was as sick as a dog when he left the restaurant last night.

as sly as a fox

- smart and clever
The manager of our apartment is as sly as a fox.

as strong as a horse/ox

- very strong
The man was as strong as an ox and easily helped us move the sofa.

as stubborn as a mule

- very stubborn
My friend is as stubborn as a mule and you can never make her change her mind.

as weak as a kitten

- weak, sickly
The girl is as weak as a kitten and cannot carry the books.

as wild as a tiger

- very wild
The little boy was as wild as a tiger when we were trying to look after him.

Source: http://www.idiomconnection.com/animal.html