Shabbat: Trapping/Releasing Animals

You may not trap wild animals on Shabbat (or on a Jewish festival). You may release a wild animal that is trapped in a trap or cage by opening the door or gate, but you may not move or lift the cage when the animal is in the cage.
Note The question behind this was asked by my niece Eliza when she was 6-years-old—ANYONE can ask intelligent and useful questions!