Specially this part.
[quote=deriving drunk]
In my experience, most dog attacks occur on their home turf, be it their home or immediate surrounds, ie they are defending in a territorial manner. Occasionally packs will feed off each other’s energy, etc. Is it a real risk? Sure, but extremely uncommon.
[/quote]
I’ll expand that a bit to include the event the OP described where a dog on lead was involved with a dog off lead and violence erupted. Dog behaviorists use the term barrier agression. Dogs will often display agression on one side of a fence towards a percieved threat on the opposite side of the fence. But home territory is only a piece of that puzzle. Same thing can occur when one is on lead and one isn’t. (Or two on lead, for that matter.) The one on lead has greater exposure to threats, and is much more likely to display agression. In most cases, it has nothing to do with obedience, it’s temperment. Which makes it extraordinarily risky walking a dog on lead through a dog park with dogs off lead, even with a well trained dog. (I know all hell would break loose if I tried that with my main dog.) A few dozen dogs off lead are unlikely to fight. (not never, just unlikely)
