The private pilot was landing at an off-airport site under Title 14, CFR Part 91, to look for a suitable place to hunt. Prior to landing, he said he flew over the landing area several times to survey its condition. The pilot said while taxiing to the edge of the landing area, the airplane's tires sank into a hole, causing the airplane to nose over. He said there were no mechanical problems with the airplane prior to the accident. The airplane was examined by the National Transportation Safety Board investigator-in-charge (IIC), and the IIC discovered that the right wing, left wing, and left wing forward spar sustained substantial damage.