There is no 100% effective way to control theft.I've seenmetal boxes on ebay that you can buy for most camera models. Then you can use a steel cable with a combination paddlock to secure that to the tree (I've always heard these called python cables). This is going to prevent theft by the average guy walking in the woods, but even these aren't 100% effective. It is amazingwhat someone lazy enough to steal your hard earned camera will do to get it. I've heard of people even cutting down trees to steal the camera. If they just put that time and effort into something productive they could afford to buy their own camera.

You also have to worry about people vandalizing them as well. (think of some redneck with a gun and what your average country road sign looks like on that one).