I have never been bitten, but I think I was 'headbutted' as you describe it the other night while feeding. I was moving one my females from the gram weigher to the feeding container and she just kind of threw herself at my hand. I think it was hind of a closed mouth strike, she could have just been trying to scare me off. She is always a bit overzealous though. My roommate, however, got bitten the other night by our largest girl.