> I have seen  black bears roll over a large dog kennel 
> type bee enclosure that was perhaps 15 X 15 feet wide.  

The mass of the trailer itself seemed to have prevented 
this problem in my experience. 

> I saw evidence that bears were pulling back the 
> heavy wire fence

That would be a workmanship issue.
Welding heavy-gauge wire loops through the fencing and 
around the structural supports might be the difference.
The bent-wire clips are useless - even a St. Bernard can
deform them by merely leaning against the fence, so any
bear except a cub could do the same.  When in doubt,
weld that metal, including all the "friction-fit" fence
structure components.  Bears can't weld worth a darn.

Keeping everything tight is important. 
Bears will play with anything "loose", and they are
easily amused.

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