I have a 1 year old Khaki Campbell and two 4 month old Cayuga Ducks. All male. Since we build the a nice big pond the Khaki Campbell is trying to bit the others in the back of the neck and try to sit on them in the water and i am scared that he will drown them. He never did that in the small pool. Why he does that i do not know. Can somebody help and tell me why?