I've heard various rumors that dogs might help keep bears away, or might be a bear attractant. Is there anything more concrete than anecdotal evidence to go on?
From the companionship end, they are a net positive, helping to calm your nerves when you hear a strange noise (though it can be disturbing when they start growling at some unseen / unheard shadow in the night).
Keep your dog on a leash.
According the the Scouts, dogs are a bad idea in bear country.
Leave your dog at home. A dog often infuriates a bear and may come running back to you with the bear in pursuit!
New Hampshire department of wildlife agrees that, while small, the primary risk is that your dog agitates a bear then runs to you for protection with the bear in pursuit.
Denali National Park, with similar advice
Dogs can sometimes keep bears away from a camp, but very often, a dog initially chases a bear and then the bear chases the dog right back to the camp. Dogs may also harass a bear unnecessarily or pique a bear's curiosity. Dogs must be kept on a leash while in the park and are not allowed on trails, in the backcountry, or left unattended at any time.
There are more than a few bear attacks where a bear has attacked a person after chasing a dog to that person, even in suburban neighborhoods. So this is not "well it's not likely but just in case advice". Conversely there are virtually no reports of dogs saving their owners from bears. Usually it's the owner having to save the dog.
It's very clear that a free running dog in bear country will increase your risk of hostile bear encounters.
In general, I wouldn't recommend it, although it would probably be alright for a short trip.
First of all, a bear has no fear of a dog, and they aren't really going to be too deterred. The fact that you are making any noise will let the bear know you are there, and should encourage it to go away, so it would be a slight benefit.
In the event of a close encounter, if a pet is let to go free, they might treat the bear like they would a human, getting close and barking. Well, that would be a very poor strategy for a bear, likely resulting in serious injury to the dog. Likewise, if you were to tie them up, it would likely lead to trouble if a bear should come in the camp.
I would say for a few hours, it probably wouldn't hurt, especially if you are in black bear country. If you are in Grizzly Bear country, or on an extended outing, or just want to be safe, leave the dogs home.
I can say that the behavior of the owner can affect your safety with taking a dog into bear country.
Taking a rambunctious dog off-leash into bear country can mean the dog chasing a cub up a tree, which I have seen before on the Appalachian Trail. It's miraculous that the mother bear didn't go after the dog or its owners after that.
As far as I know, keeping the dog on a leash and keeping it with you at all times will not increase your danger in bear country.
Live in the Ozark National Forest. Specifically where the game office drop off bears that are written off as "trouble makes" caught near residences.
Last March I was charged by a rather large, male, black bear...the only thing that saved my bacon was a dog named Doo. Not "Scooby-Doo", but "Doo". Then there are the dozen or so encounters where the bears came into my yard that Doo ran up a tree. Then there was the time a bear busted out two of my windows. Bears here are not afraid of people.
Long story short...a dog is a must. If you walk in brown/griz country...I'd take at least three. Don't have to be big dogs. Funny thing is...black bears can count. They tend to think twice with one dog, but two dogs....they will take cover rather than advance. Three dogs...no worries.
Half guard dog and half hound is a good bet. Best of both worlds without them straying too much. With that said you don't want the "half-hound" to be red-bone, blue-tick or any other hound adept at running 20 miles a day. You will loose them in short order. A mild hound like a "water-dog" (lab/weimeraner) mixed in with a BIG guard dog (mastiff/dane).
Any LARGE pure bred guard dog will do, but they cost money while muts are typically free. Even a single teacup poodle is better than nothing...assuming you can out run the dog of course. A single pitbull will work, but you can't run more than one cause they'll fight your other dogs if not kill them.
With my experience with black bear... I'd never test my luck with brown/grizzly.
It depends on the dog.
Dogs have far superior senses to humans, which is why dogs became man's best friend, it was mutually beneficial for us to coexist. Early man gave docile wolves their scraps from their kills, and in return, the domesticated wolves provided man with an early warning system against predators and other enemies. Protection from large predators such as bears and wild wolves is exactly what dogs were originally kept and bred for.
I'm from wild bear country, where no one goes out into the woods without some sort of bear protection. Usually that bear protection is a shotgun or a large rifle, next to that, they take dogs. Bear spray is one of the last things they consider bringing with them (except for in certain national and provincial parks where dogs are hardly welcome). I feel infinitely safer hiking with my dog than I do with a can of bear spray.
I've encountered several bears while with my dog. The first time was when I was only 10 years old backpacking with my Dad, we had our pure-bred German Shepherd with us off leash in Height of the Rockies Provincial Park. She was leading the trail when all of a sudden we rounded a corner and found her with her hair raised looking up the mountain into the trees, she let out one insecure bark after which it sounded like the forrest started to come down. Not far up the hill was a huge Grizzly, who was startled by the bark and started crashing through the bush to get a safe distance before turning to check us out. We quickly moved on and the bear didn't pursue us.
Dogs are also great for sniffing out bears that you don't yet see, and scaring them off before you encounter them. My current dog is a German Shepherd/Black Lab cross (who more often than not gets mistaken for a black bear by other hikers), and he gets very aggressive and intimidating when he catches a whiff of a bear on the trail ahead. He doesn't chase them, but his barking seems to be enough to warn the bears that we're approaching and scare them off.
I think it makes a big difference what type of dog you have and how well they behave. My dogs all grew up hiking in the woods, they've met all sorts of wild creatures and they've all been obedient enough to come when called and not give chase when commanded to stay. The dogs that would give you problems would be the little ankle biters that yip at everything and don't listen to anyone, I can see one of those antagonizing a bear, because they aren't intimidating, and are more likely to be pursued as food. The reason parks say keep your dogs on leash, or don't take them into the backcountry at all is because far too many people that visit parks have stupid disobedient family dogs that spend most of their time tied up in the back yard or at the end of a leash, they don't know how to behave in the woods.
Dogs are excellent protection from bears, especially in numbers, but they must be the right breed, the right temperament, obedient, and large enough to intimidate a bear.
Height of the Rockies Provincial Park is an example of a park that doesn't say, "Keep dogs on leash in the backcountry." instead they say, "Dogs in the backcountry must be under control at all times." If you have an obedient dog that comes when he's called, and doesn't chase every critter that he encounters on the trail then odds are good he'll do more to deter a bear than provoke one as long as he's got a big enough bite to back up his bark.
