They have to put them in cages in order to keep them from running all over the place.
Women are the zoo keepers.
That is what marriage is, don't you think, we try and tame them. So maybe it's like a circus, not a zoo. The letters come in the mail, or at least they are dropped through the mail slot in the front door. The script is neat, italic and the writer considers them love letters. But not when you are with anyone.