Sudden aggression in female rat?

[AmeliaArms]

My female rat (approx 11 months old) has suddenly turned very aggressive. I got her about 10 months ago as a companion for another female rat who has since passed away and she has always been a happy, friendly and cuddly little girl. About two months ago her companion sadly had to be put down due to some health issues but I have got her a new little friend who would be close on three months old now and has been with her for just under two months. She accepted the new rat straight away and had no issues with her at all, they were sleeping together and playing together from the get-go and she has been fine up until now. She usually comes running to the cage door when she hears me call her name and is itching to be picked up and played with and loves being handled. Today, however, when I went to take her out of the cage she was hiding under a ledge in the cage and refused to come out. When I tried to coax her out by trying to pat her she attacked my hand and bit me, drawing blood. I then tried with some food and she attacked the food like it was an enemy. If I put my hand anywhere near her she lunges and tries to bite. I tried talking to her and trying to soothe her which seemed to work. She came out from under the ledge to the door of the cage but as soon as I tried to touch her she went feral again and tried to bite me.

She has also suddenly become very aggressive towards my other rat who has been hiding from her all day. I took my other rat out and gave her a cuddle and as soon as I put her back in she was attacked by the aggressive one and I had to separate them.

I have no idea what could be causing the aggression because she is in good health and was in high spirits up until this morning. I'm very worried as I cannot get a hand on her without being bitten and my other little baby is distressing as her friend keeps trying to attack her. Does anyone know what could be causing this?

[BostonRatLady]

Is there a possibility that she could have been injured or gotten hurt?

[Anjel]

I would first suggest trying to check if she is sick or injured. Being hurt can manifest in many ways in rats, and aggression is one of them.

Have you gotten any new pets, clothing, etc lately, or been around any new animals? I've had rats that would attack my hands if I smelled like any of the stray cats outside, or if I played with the dog and didn't wash my hands.

Check for injuries if possible, using thick gloves will help you handle her.

[Violet976]

Is there *any* possibility of the new companion being a male? Just wanting to make sure she isn't pregnant.

Otherwise, I'd be most worried that she is injured. They hide their injuries well, and can many times become aggressive when they aren't feeling well.