Our home is located on an open area. Behind us is a tract of "no man's land" where people always take their dogs out for a run (or take themselves out for one!).
It's amazing how our dogs react to others. When the two German Shepherds go by, they watch but they're quiet as mice. When the Rottweiler and his master come, they hide behind the barbeque and wait till they've passed. When their friend Jasmine, a 9 month old Golden Retriever goes for a walk, they're all friendly yips and tails wagging (even though Jasmine is 10 times their size). When the big lab Buddy from next door comes for a visit, there is a lot of tail wagging and nose-to-nose greetings. When the collies come by, look out!
I don't know why they hate the collies, or should I say they each love to torment the other. When the collies come by, they wag their tails and happily yip as they go past. This drives our dogs to distraction. They can hear the collies coming from a mile away and are perched at the end of the patio yapping incessantly at them. When our dogs go for a walk and the collies are behind their chain link fence, our oldest struts back and forth in front of them yapping and yipping like he's the happiest dog in the world. Our youngest is a bit of an ape...he just copies his older brother. The collies go crazy. I have a heck of a time dragging our oldest away from the pen. But a couple of hours later, when the situation is reversed, our dogs are in a frenzy when they see the collies going by.
I suppose dogs are a lot like people...we immediately sense whether or not we like someone on a first meeting and react accordingly. We either defer to them, taunt them or become friendly with them. Dogs, it seems, have their own criteria for those who are acceptable and those who are not. I'm not sure what it is, but it is very interesting to watch.