They can pretty much take down any kind of fencing if there is something they want on the other side. I only have chicken wire up so mine aren't very secure. I do live in the middle if town, never actually seen a bear in my neighborhood but I know others have. I came home from a 3 week vacation and found bear scat in my garden. I am a bit nervous about this spring. Time will tell.
The biologists here in Kodiak, AK supposedly the home of the biggest brown bears in North American use simple electric fences to keep the bears away from thier food which is in bear proof containers set in the middle of like a 10'X10' area. They also string the stuff up around their tents. Bears are curious creatures and they love investigating things. For us in Alaska the time to worry is spring and fall. They are hunger when they get out of their dens and they want that extra bit of fat before going back to bed for the winter. Electric is cheap and easy and supposedly very effective and thats straight from a head bear biologist from Kodiak. But there isn't much thats gonna stop a bear they are pure strength. The black bears can climb so that adds to your delima.