My rat Wally (~1 year old and 11 months in my home) was kind of aggressive as a pup, but through lots of time and patience he stopped biting, lets me pet him, and will do a few tricks for treats. Nowadays he's mostly well-adjusted but with a dislike of being picked up. However, every time I try to clean the cage he goes completely berserk. It can take 2 hours to do a 15 minute job because I have to keep luring him away from the cage and giving him time-consuming treats to keep him distracted. Otherwise he will attack my hands. It's not that he feels cornered in the cage; he will run across a room to patrol it. I thought that as he got use to having his cage refreshed his behavior would calm down, but it has gotten worse over time. He no longer gets distracted by treats, and today he leaped from the top of his 4.5 foot high cage to land on my hand and rip into my fingers (twice). There was lots of blood. He definitely doesn't think my hands are food as he is extremely gentle when accepting even the smallest hand-fed morsels from me. He also has never tried to bite any part of me except the hands. This beserker behavior also happens when I try to give his cage mate Darwin a bath to control his buck grease. He will puff up, start chuffing, and viciously attack his friend (they sometimes play aggressively, but this is something totally different with blood, hair flying, and screaming rather than squeaking). It takes about three days for him to finally stop trying to attack my other rat, even if he was only bathed in water with no soap. He started behaving this way with an older rat I used to have and the behavior became so permanently agressive that I had to separate them until the day my beloved older boy passed. I cautiously keep Darwin separated from Wally when he behaves like this and will nightly switch off who sleeps in their main cage and who sleeps in the auxillary one in order to try to balance out their body odors, but it's kind of traumatizing for Darwin even if he does (slowly) forgive and accept Wally back each time. While he's in this berserker stage he will destroy everything from cardboard hideaways to wooden ladders with frantic chewing. I'm sure this is some sort of scent-related territorialism, but I don't know what to do about this behavior. I don't clean the cage as often as I would like or keep Darwin as groomed as would be preferable, because I'm honestly afraid of triggering Wally. Neutering him is not an option since the only vet in the area willing to treat rats has quoted me a price of almost $300. I would love to get Darwin a more even-tempered cage mate, but as long as I have Wally I'm afraid to even try introducing another rat. I would like to rehome him but can't surrender him at the shelter because I can't guarantee he won't bite. I also can't really give him to someone else for the same reason. I'm not inhumane enough to set him lose in the wild or try to have him put down; I do recognize I've made a commitment to his well being and will honor it. I'd just really appreciate suggestions for how to control this kind of aggression or ways to rehome a rat with these problems.