I've had ferrets for just about a year now...
2 boys: Dante (4, big, albino, being aggressive) & Bandit (4, blind, IBD, cancer, gentle as can be). 2 girls: Enix (1, crazy, naughty, adorable) & Khaleesi (found outside 4/3/14, seems under 1, timid, sweet)

Dante has always been aggressive when he plays, which is why I adopted Enix....Bandit couldn't handle him. It worked out great, but lately Dante has been grabbing Bandit by the neck and shaking him as hard as he can. Then Bandit screams and seems terrified (I mean...he's blind. He doesn't see it coming) and he follows Bandit, often having to be separated long enough to calm down. Scruffing doesn't help. He does the same thing to Khaleesi and seems to be doing it more since she was brought home. He very much wants to mount her, which he has never done to Enix. He's even more aggressive in his play with Enix lately. Enix is definitely fixed, as are Dante & Bandit. I have no idea about Khaleesi's history. She was very thin and exhausted when found in the snow. 

Is this just a male thing? Should I be worried? He seems very healthy....he's a big ferret, he plays with me, he gives lots of kisses and he seems to understand that the food area, cage and litterbox are off limits for biting the other 3. I am just constantly "saving" Bandit and Khaleesi, especially Bandit when he's trying to sleep on his bed. They all cuddle in the cage without issue, and outside of the cage when Dante isn't feeling playful. 

Dante has, at times, gone after my cat. He seems to think it is fun. But one time my cat tried to bite me and Dante ran, out of nowhere, and chased my 20+ pound cat out of the room for it.