Guard dog

Both guard dogs and watch dogs bark to alert their owners of an intruder's presence. The barking is also an attempt at scaring away the intruder. The watch dog's function ends here, while a guard dog might be trained to restrain or attack the intruder. For example, livestock guardian dogs are often large enough and strong enough to attack and drive away predators such as wolves. In cases where intruders are more likely to be human, guard dogs are sometimes trained simply to restrain an intruder with his owner's guidance, as in Schutzhund training. Occasionally, guard dogs are trained to attack human intruder(s), though this practice might be locally illegal. Some breeds (such as Keeshonden) are excellent watchdogs but not so excellent guard dogs, as they bark loudly to alert their masters of intruders but are not given to attack behavior.