Going by my Government course in black bear attack survival, I'd add to Smoke's post, that over 90% of black bear attacks on humans are fatal to the victim.

The attack could be for protection of young by a sow, or protection of food by either sex - a young 3 year old strutting his stuff who still thinks Mom's handy to protect him if he gets in over his head, or by any sex for food, as Smoke indicated. When a bear steps out onto a trail in front of you or behind you, he is sizing you up for a meal. Believe it. He knows you are there - excellent sense of smell and hearing. Get an ichy or twichy feeling something's watching you- look behind you and there's a black bear? He's just sizing you up. He walks into the bush - in a few minutes 'another' bear walks out onto the trail in front of you? Same bear - still sizing you up. The frontal assesment is because you didn't scare him away when he was behind you looking you over. If he doesn't spook from you, the next time you see him might be from the side as he bursts out of the cover to run you over to get you on the ground - it will be a silent attack - at 30mph. Something to think about.

The reason most grizzly attacks are not fatal, is due to most grizzly attacks not turning into a predator attack on the victim - they are usually an aggressive attack to show superiority and to beat you up. Yes - you might need 600 stitches and/or might die from loss of blood if help isn't close enough. The difference is that most black bear attacks turn predatory and you become a food item during the attack.

This is as I understand the black bear/grizzly main attack differences. Of course, you never know what it is during or before and to fight back is your only choice. Play dead with a black bear and you will be. The easier you are to kill, the more likely he will think all humans are food items. I just couldn't play dead in a grizzly attack, I'm sure. Fellow just 60 miles West of here killed the sow that attacked him, with his hunting knife. He survived, she didn't.

Sheldon taught us to always pack the means of bear defense - for us, that was a slug loaded 12 bore. We found in town here, that buckshot is useless beyond about 15 feet - whereas slugs work every time. I'd rather be packing round ball loads, myself, to the performance of 1880's African round ball loads for a 12 - more effective than a hollow slug, especially on grizzlies - although store bought full sized slugs are better than sabots and buck. I was told by a parks ranger than buckshot point blank in the side of a big grizzly only pissed it off - didn't penetrate beyond the ribs but really make him mad. When he stood up, the other guy put a 1 1/4oz. Fed slug into his chest, which broke his spine.

In general, bears have small, light rib bones, but can have much energy absorbing hair, thick skin, fat and muscle outside the ribs to slow the lighter projectiles.

BBears are usually easily killed - but of course, the bigger the bear, the bigger the bullet - imoh.

If you cannot pack a gun, then a sharp blade of at least 8" length was his suggestion.