new biting behavior, in an older female

[pinkies_mama]

One of my older girls (20 or so months) Molly, has developed a recent new biting behavior. She'll nip at the ears of her roommates. At first, she only did it to the younger girls, who are at least half her age. But then she started doing it to Izzie, whom she has been with from the beginning. We thought Molly was getting back at the little girls for picking on her, but then she started nipping at Izzie. Its not hard, aggressive biting, more like warning bites, but there really isn't any reason for it (that we know of).
Any ideas?

 

[lilspaz68]

Is she nipping or grabbing and pulling her around?

 

[pinkies_mama]

No grabbing or pulling, just a quick swipe/nipping. I know its a pretty normal behavior, its just new and she has never shown any signs of aggression in her life. She is usually the one getting pinned.

 

[jorats]

Some rats can get grumpy at that age... some have seen a behavior change with a pituitary tumour. I'd keep a close eye on her.

 

[pinkies_mama]

some have seen a behavior change with a pituitary tumour. I'd keep a close eye on her.

I will certainly be on the look out. Thanks everyone.