How do i know my rats in heat?

Question
I have an 8 month old female dumbo rat that i am wanting to breed. She is very sweet and the male dumbo rat i am going to breed with her is a sweetheart as well. my question is what are some ways i can tell she is in heat or on her "cycle"? is there one way that is 100% garuntee of being correct?

Answer
Rats come into heat every 4 days for about 12 hours. Mostly, you may notice she's more playful and when you scratch her back she may arch her back, run forward, and stop with her ears vibrating and tail stiff. Some rats never really display.

Do you know the genetic history on these rats? I'm always sure to mention how it takes more than just a sweet temperament to ensure a healthy, happy litter. Keep in mind that many things happen during pregnancy, labor and delivery and that sometimes your Doe may not come through it all right. You may lose babies, lose her, or lose all of them. I'm not trying to preach, just want you to be sure you've done your homework on it. :)

Good luck!