I have two 7 year old guinea pigs called Daisy and Hazel. Recently, Daisy has really started biting me, like really clamping down on my finger and trying to tear it off. She's ok in the hutch, she'll lick me then, but when I pick her up she will just bite my finger. She has never done this before, not even if she wants the toilet, and I just want to know what's up with her.