Rescued Rat Attacking Resident Rats

Question
Hello, I had two 1 year old rats that I bought at a pet store.  We decided to expand our family and we adopted a rat from a rodent rescue center.  We were told she was about a year old and had been fixed.  The introduction seemed to go well, and we've had the new girl for about 4-5weeks now, but during play time she tries to bite the resident rats' ears.  The resident girls have never attacked her in any way, and they cuddle her during nape time.  When I asked the vet I was told they had to work out a pecking order and that the scuffles should stop in 2 weeks. It's been about 5 weeks now and the new girl keeps biting the resident rats' ears.  She drew a drop of blood once, and I feel really bad for my resident girls. I have no idea of knowing what the rescue rat's life was like before I got her, so I don't know if that has anything to do with it.  I've tried smearing peanut butter on their backs so they could lick it off each other and bond.  I've tried snapping, clapping, and flicking when she attacks and that doesn't seem to keep her from doing it either. I just don't understand how they could all be so cuddly with each other while sleeping, but during play time not get along.  Any advice on what else I could do so my rescue rat stops attacking my other rats.

Answer
The Vet is right about the pecking order and yes, it can be frustrating as heck too.  However, do not discipline her in any way when she bites the other girls as this is showing negative energy and will only make it worse.  Chances are she was bullied before and she is trying to make a point now. To be honest if the other girls didnt like her they would not cuddle when they sleep and allow her to join them in their nest during their daily slumber.

A word of warning about peanut butter too: not only is it not good for them (fat content and protein levels are out of this world!!) but it can be dangerous as well. Sadly I have witnessed at the clinic rats are brought in by frantic owners after they fed the rat even a tiny taste. It clogged their throats and they choked to death.  Very terrible to witness. I tell people if for whatever reason they insist on using it to water it down first.

Anyhow, what you can do about the ear nipping is try the same approach as you would for biting. If this happens during play time, remove her from the play area and put her back in the cage. If you see her getting ready to do it, pull her away and get her little rattie mind on something else. Also, reward her with a treat that is reserved only for this "session".  Cheerios, whatever you usually dont give them on a daily basis are fine. I go to the baby food section and buy the Gerber Finger Foods Fruit Puffs and they devour them, esp the strawberry ones and the sweet potato flavored are a hit, too.  Low in sugar and proteins, they are really nutritious either, but for a training snack they are great.

She should soon learn that her behavior is getting her either put back in the cage and making her miss play time or when she has a positive experience with the other rats she is given the snack.