After going into heat, an un-spayed female ferret can actually die if she does not mate. She will remain in heat until she mates, and if she does not, the excess estrogen will cause anemia and eventual death.
DID YOU KNOW? Marlon Brando hated memorizing lines so much that he posted cue cards everywhere to help him get through scenes.
He even asked for lines to be written on an actress's posterior. (That request was denied.)