I've been trying to find some more information about undersocialized rats and their potential for aggression to rats upon introductions/eventual living together. There is a 7 month old intact male at the SPCA who was surrendered two months ago due to owner's inability to care for him. He wasn't surrendered with any other rats, so I suspect he was being raised alone/neglected. He has spent the last two months alone at the SPCA without rat socialization, and I'd guess limited human socialization due to his label as "nippy." I visited the fella earlier this week and he is quite skittish and did nibble at my nails (never bit my flesh). At one point he did climb halfway onto my hand, enough to allow me to pick him up. I gave him a feel for lumps, pulled his lips back a bit to check his teeth, and he didn't bite me. A small child also placed her hand into his encounter and was not bit by him. There was no reported bite history by the family that surrendered him, but he is labeled as being nippy. After I put him back into his cage he had quite a bit of porphyrin discharge from his nose, possibly as a result of stress from being handled? I'm considering rescuing this guy, but I've got three spayed female rats ranging from about 1 to 2.75 years of age. My first priority is the health/safety of my girls but I do feel very sad for the deprived life this male has been living. I'm not sure that I'd label this guy as aggressive, based on how he interacted with me. But, I am concerned about potential aggression he may show in more threatening situations (e.g., vet examination, establishment of dominance hierarchy). When rats have had virtually no socialized from rats/humans by 7 months of age, is it kind of a lost cause by that point? Or is it possible that he could be socialized enough to be able to live with other rats and be around humans peacefully.