I am surprised that the lab rats bit, but I guess it depends on how/why they were handled.
I bought Angel for my son when he was eight. I wanted to tame it before I gave it to him so that he didn't get bitten. I took the rat to work and kept it in an aquarium in my office. I would put my hand in there several times a day, starting on the opposite side of the tank and inching forward until I saw some stress and them would back off. By the end of the first day, she would go to a corner and hide her face when I pushed the contact. the second day, when she hid her face is barely brushed her fur with a finger. She slowly untucked her head and slowly and very gently PUSHED my finger away with her nose and tucked her head again. I thought, "Wow, that was loud and clear. She is not quite ready." She could have struck out at me and nailed my finger, but she was just scared. It didn't take long for her to realize that I was her friend and she loved everyone in the family, but I was always her favorite. The only time she ever bit was when I had something yummy smelling, like weiner juice, on my fingers and she wanted to taste it. Even then it was a squeeze with her teeth and not a puncture.
She would sit on my shoulder and put her little hands on my cheek and lick my face like a dog. I had hamsters as a kid and they would bite, and sleep all day, and not want to be touched. Not Angel, she stayed in my son's upstairs bedroom. Sometimes, when she got out, or was left out of her tank, I would find her curled up on the pillow next to my son's face, or she would come down the stairs looking for me. She never hid from us and always wanted to be where we were. The only thing that I didn't like about her was that if she was left unattended on the bed, she would bite tiny holes in the sheet. I still have sheet sets with random, tiny holes in several places.
She got downright decrepit at 5. She began to lose use of her back legs and her bowels but still loved being carried and petted. One day my then 14 year old came outside to me and he had tears in his eyes. He was holding her in both hands and she was fading. I asked if he wanted me to put her down and he said no, he just wanted to walk with her (she always enjoyed being outside, but preferred to be held because 'the great outdoors' scared her a little). That child walked around and around the house, squalling and kissing and talking to that rat til she died. It was so sad to watch, but I couldn't help but think what a glorious life it had been for one rat.
