I'm really surprised he doesn't bite you to. Once they get to adult stage drakes can become a hand full, and if they have ladies with them even more so, hormones just do it to them, so he is actually chasing people? you need to get them to stop running away, stand their ground either with a broom placed between them and your drake or a spray bottle full of water. now if you use a spray bottle it has to be quick and a surprise usually they will stop in their tracks if sprayed in the face . Now if you use the broom don't hit him with it's to stop him from getting to close , close enough to bite. Back him up with it too, you are leader in the pecking order not him. Teach others in the family to use these tactics. and Welcome to BYC.
