My bullterrier is 1 and a half years old (male). We decided to get a female bullterrier and she is now almost 3 months. When whe introduce her to him he is all over her and barks and bites or nibbles het in the face, legs and neck. When she sees him she rolls over onto her back and stay in that position. The mail bullterrier is ver bery raugh with her and is afraid that he would injure her. I did put mesh on my front gate so that they could interact through that but he bites the mesh and he makes a growling sound but the pup never runs away she always goes back to him. Should I be concerned about his behaviour or is that normal