I have a 5 month old male cocker spaniel (Victor) who has been adorable and really lovely up until recently when we got a new kitten. Victor plays really rough and bites it really hard or even pulls it around by its leg. When myself or any other member of my family scold him for it he becomes aggressive-shows his teeth and tries to bite the hand that either holds him or points the "no!" finger. And when I say bites, I really mean it! From what I have gathered he is jealous of the 2 month old kitten. However, he is not always rough with it and the behaviour seems to escalate when I have been really friendly to Victor- so now we have reached to the point where we can't really praise him or touch him, because straight away he focuses on the kitten and runs for it! What do I do?We really love him and this awful behaviour only appears when the kitten is around. At night, when we put the kitten in a different enclosed area of the garden so that it can go to sleep, Victor seems to become really mellow and lovely again. It's like having two different dogs! Please help! PS 1.We have a big yard where he can roam free and he is regularly walked, so I don't think it has to do with his energy levels. 2.We also have a few teething toys for him which he loves. 3.By scolding him I mean starting by saying "no" firmly(which is when he shows his teeth and tries to bite my finger) and escalating to holding him down in order to become submissive because otherwise he jumps at me and bites anything that is 'biteable' on me! 4. I have insisted that no-one plays "bite my hand" games with him from day one, so he never bites anyone at any other time!