Why teaching your dog to “leave it” will make your life easy and the local environment safer.
Puppies love to chase things: toys, balls and even other puppies. They also like to chase things they shouldn't, like small children, protected wildlife, cats, and cars. The time to teach dogs not to chase inappropriate things is when they’re young. It's much more difficult to teach this to an adult, so take advantage of your puppy's youth and do it right away.
When a puppy chases something or someone, they are looking to play. You must teach your puppy what is okay to chase and what is not. Balls, toys and other dogs who want to play are fine. Protected wildlife, small children and cars are not. The best way to teach your puppy not to chase things he shouldn't is to teach him the “leave it” cue. “Leave it” is used to stop your dog from doing something he shouldn't.
To teach “leave it,” put the leash and collar on your puppy and have him sit. Hold on to the leash and drop a treat in front of your puppy while saying “leave it.” when the puppy starts to move toward the treat, repeat the “leave it” cue.
When your puppy just sits and looks at the treat but doesn't move toward it, turn him around to face you and praise him. Do this one more time. Then give your puppy the treat by handing it to him.
Once your puppy is reliably leaving the treat when you tell him to, a better option to increase his temptation is by using something even yummier, like a piece of chicken or one of his favourite toys. Keep working at this until your puppy will “leave it” every time you ask, even off leash.
When your puppy learns the “leave it” cue, you can trust them and use it to help keep the environment safe and stop them from chasing. Once they hear “leave it,” they will know that whatever they’re pursuing is off limits.