Your dog probably doesn’t have anything personal against the mailman. He’s just taking care of his own. In fact, it is safe to say that every dog has a little watchdog in him. It’s something that dogs inherit from their ancestors, who had to defend their territories and limited food supplies from trespassers.
To a dog, the great thing about mailmen is that they appear to be easy targets. Here’s what happens:
The first time a dog heard this stranger coming up the walk, he got alarmed. He probably backed up a little bit at first, but one brave day, he gave a little bark. His owners came running to see what was causing the commotion. The mailman, of course, dropped off the mail and left. The combination of praise from his owners and the mailman’s retreat makes dogs very happy. They just assume that they scared the mailman off. From then on, they feel confident that they can protect their homes from these fearsome visitors, so they keep barking.
Mailmen, meter readers, United Parcel Service and FedEx couriers, and any other stranger who purposely heads up to the house and then looks as though he’s retreating when he gets barked at is going to get the same reception.
Nearly all dogs have an instinctive urge to protect their homes, but that’s not the only reason they kick up a fuss when the mail arrives. Part of it is merely anticipation. Dogs are attuned to rituals and routines to such an extent that they’d probably be called obsessive-compulsive if they were people. The mail comes every day at more or less the same time. It doesn’t matter whether this event is happily anticipated or thoroughly dreaded.
Dogs probably begin thinking about it when they get up in the morning, and their excitement grows as the time approaches. By the time the mailman finally arrives, they’re keyed up and ready to rumble. It can get to be the high point of their days. Dogs who spend their days alone get particularly excited because they feel as though they’ve been left in charge. If they don’t bark like crazy and warn off intruders, who will? They figure they’re on duty should anyone approach their property.