About 5 months ago, I bought two baby brother gerbils from a local pet store. I have a busy schedule so I'm sure they didn't receive the handling they should have for proper taming. But when I could we would "play". I often feed them treats through the bar of cage or by hand. I have a play area for them to stretch their legs out in and we do that once a week. One of my gerbils never likes being held. I try to talk sweetly and scratch his head but he usually fights so I put him back down. However my other gerbil he after the first few times of struggling a little calmed down and now lets me pet him and hold him some. They've always been curious and climbed onto my hand, they've never shown fear. However my "tame" gerbil has done a complete 360. Everytime I put my hand in the cage for things...like feeding and putting in toys etc. He attacks me! the other does the same as he always had...comes out to see what's going on and sniffs me or takes a treat, no biting. The other gerbil no matter what i'm doing...even when my hand isn't moving he jumps at me and bites. I've tried washing my hands...I even had someone else put their hand in and he reacts the same.
I was wondering if anyone has ever had this problem. I read that gerbils aren't normally aggressive....This is my first time owning gerbils so i'm not sure what the next course of action should be....help

