Guard dog

A guard dog, an attack dog or watch dog is a dog used to guard against, and watch for, unwanted or unexpected people or animals. The dog is discriminating so that it does not annoy or attack familiar people.Both guard dogs and watchdogs bark loudly to alert their owners of an intruder's presence and scare away the intruder. The watch dog's function ends here; a guard dog is capable of attacking or restraining the intruder. For example, livestock guardian dogs are often large enough and strong enough to attack and drive away livestock predators such as wolves. Some breeds (such as Keeshonden) are excellent watchdogs but not excellent guard dogs because they bark loudly to alert their masters of intruders but are not given to assertive behavior. Similarly, even very small but attentive dogs (among a few other species) may function well as watchdogs.