Rats definitely prefer to be housed with other rats. They can get depressed, or OCD (like I suspect your guy may be) without a partner. You can get him a male rat partner, with or without fur. Male rats usually won't fight one another, since they're far more interested in being social.
They'll pee on everything in their cage though.
But the hairless rat will likely always have some scratches, just because he's hairless.
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