yes it is normal. i freaked out the first time i saw it too. the rattling is the male making sure she isnt a he. if one rattles their tail and the other rattles back that means there are 2 boys. him biting her just means he hasnt been with another girl and wants to breed. sometimes you shouldnt keep a male and female together 1 on 1 becuase they will stress each other out to death. also one could get beat up and get infections and bad wounds. this is why i keep all my animals sepperate.