You will be rewarded for being kind to animals:

A kind act, even to animals, deserves to be rewarded by God.Muhammad once told his companions the story of adrink. When he went up, he found a thirsty dog gasping in thirst, so the man went down in the well again to fill his shoe with water and brought it up to the dog. God was thankful for this man’s compassion and forgave his .past sins

On another occasion Muhammad told his companions and confined a cat until it died. She neither fed the cat norlet it go. (Sahih Al-Bukhari, 3071)