Thankfully, rarely in my case do I ever encounter dogs when I'm out photographing wildlife but I'm mostly a fair way from civilastion by the time I set up. To be fair, most dogs I do meet are fine and I now know some of the owners too. Most owners call their dogs in if they see me.
However, I would never trust a dog I don't know and this is something we've drummed into our 11 year old daughter, as she has in the past, walked up to unfamiliar dogs to pet them. Safe to say, as parents, we soon stopped that.
I'm not keen on Bull Terriers, I tend to give them a wide berth if I encounter one, That's not having a go at them, I'm just not keen on them and I'm sure, in the majority of cases, they are fine and well behaved but I will remain cautious around them, to be safe.
A trick my father taught me when I was a lad was that if a dog is approaching you and it looks like it could mean business, bend down as if you're picking up a stone or rock. Most dogs seem to instinctively back down and most turn on their heels. I'm not sure why or how it works but it seems to, in most cases.
When I have had a bad exprience whilst out, and I could probably count them on one hand, it's not really the dog that is the problem, it's the way they're handled. For example, a dog off the lead in a play park is asking for trouble, even with better behaved dogs. I've only had one bad encounter I can recall whilst out photographing wildlife and it happened this year. Long story short, I was heading back to the car along the river, I heard a commotion around the corner in the water and a Border Collie was chasing a female Mallard, who I had seen with 8 chicks earlier in the day. The owner was running along the riverbank after the dog, shouting at it. I can't imagine any dog would go back to a ranting owner. I said to the guy that there were youngsters about and I got a tirade of abuse, as he ran past me, still ranting at his dog too. Why would he let his dog off in the first place if the dog was prone to chasing wildlife? Sums it up in a lot of cases.
On the other side of the coin, last Saturday, I was set up on the river, covered in scrim, with a perch out. A guy I regularly speak to turned up with his black Labrador, saw my perch, shouted was I there, I showed myself, he called his dog to heel and left. That was the end of it.
In all honesty though, some of the folk I meet on my adventures worry more than any dog I've ever come across.