accessories for bear fences: PORTABLE BEAR ALARM
This perimeter alarm (22-01 below) weighs less than half a pound and takes up less pack space than a coffee cup. The alarm has 350 feet of thin line that can be set at any height. If a bear pushes on this line, it triggers an alarm. So it helps keep you from being surprised by a bear while in your sleeping bag. And if you have pepper spray, it puts you in a position to defend yourself should the need arise.