It seems that fences are set up to prevent elephants from entering entirely. Although they are spaced widely (and a weak breakaway trip wire is strung from hive to hive), so that if an elephant is trapped, or approaches the fence violently, it can still pass through without damaging the hives.
I'm guessing that has to do with their 85% effectiveness. Most of the time the fences work, but when they don't they want to minimize hive damage.
It seems that fences are set up to prevent elephants from entering entirely. Although they are spaced widely (and a weak breakaway trip wire is strung from hive to hive), so that if an elephant is trapped, or approaches the fence violently, it can still pass through without damaging the hives.
I'm guessing that has to do with their 85% effectiveness. Most of the time the fences work, but when they don't they want to minimize hive damage.