2 Female rats fighting- drawing blood

Question
Hi, I contacted you awhile ago about my female rat having a lump on her face, she passed away on the 02/01/2010. So I thought I would get another friend for my 1 1/2 year old about 2 3 weeks ago from the RSPCA I'm not sure of her age maybe 1 year or a bit younger. I introduced them the proper way (side by side, swapping them into each others cage, all that) they have had some fights but no blood was drawn. They are living together, sleeping and grooming getting along, until today they started fighting and drawing lots of blood on the feet, body and mouth. I have seperated them now, they seem to be okay, they are eating little bits of food but staying in their houses. What should I do?

Answer
Keep them apart again and start all over again.  This is not really common for females to fight like that, esp drawing blood.  Not to say they dont get into it a little bit, but to fight to this degree, something happened that ticked the other off.  Who is the aggressor, do you know?  I would keep them apart, let them play during the DAY TIME ONLY in a secure play area where you can observe.  Dont put them together at night for a bit, because this is when rats are the most alert (the nocturnal little brats!) and seem to scrap most.  Take it slow....

How long did they live apart before the introduction?  How long have they been together before the real fighting began?   

Do they  puff their fur up when they see each other and seem to want to go at it full throttle soon as they see each other?