Big or small, male or female, young or old, any dog can bite. Even the cuddliest, fuzziest, sweetest pet can bite if provoked.
Dogs bite as a reaction to something. If the dog finds itself in a stressful situation, it may bite to defend itself or its territory.
Dogs can bite because they are scared or have been startled. They can bite because they feel threatened. They can bite to protect something that is valuable to them, like their puppies, their food or a toy.