It is natural for dogs to hunt. The idea of hunter and prey is a primal instinct. Though your dog is a domestic pet, he still has natural urges to chase and hunt. This does not necessarily mean he would know what to do with an animal if he actually caught one, but it could potentially be dangerous if he pulls on your leash or runs away while you are on a walk because he is chasing an animal. It could also be quite annoying to go outside with your dog and watch him chase squirrels and rabbits while you are trying to spend time with him. Few dog owners enjoy being pulled and tugged when they are at the other end of the leash. And few owners enjoy yelling for their dog’s attention when the dog runs off to chase a squirrel or rabbit.
Besides the obvious dangers of having your dog get away from you while leash walking in public spaces, you could also find yourself in trouble with your dog on someone else's personal property or in a fight with another animal, or even injured yourself if you are still holding on to the leash when your dog decides to chase and hunt. Teaching your dog not to hunt can be challenging and rewarding for you both. You want to be able to take your dog out on leisurely walks and have his attention not have him running off and chasing wild animals. Teaching him that hunting is not an activity you are going to do together is going to take some patience, some repetition, and extreme commitment to your dog and your desires of not having a hunting dog.
Some techniques will require treats, toys filled with treats, enough kibble for a meal each session you have with your dog, and a leash. Be prepared to spend 10 to 15 minutes training your dog not to hunt each time you are outside together. As with any other command, teaching your dog a new behavior will take time, commitment, and patience.