A watchdog variously referred to as a guard dog (more often than not the expressions are used interchangeably) guards property and safeguards humans from animal and human predators. Though watchdog breeds vary greatly in terms of size, they tend to be very vigilant, and have well-developed sense of sight and hearing. Siberian Huskies, Pugs, Alaskan malamute, Airedale Terriers, and Affenpinscher make good watchdogs.
Smaller breeds tend to be more alert than their bigger brethrens
Could be sensitive to strangers or could be standoffish (varies from breed to breed)