There is very clearly something connecting the top two strands of the fence in the bottom left corner of the shot. There is also something green (what appears to me to be a wire) that looks to be connecting the bottom strand of fence to stake in the ground in that corner (some sort of a ground maybe?). On the right side of the fence, if you look closely you can see by the twist that the fence material is some type of flat ribbon, not a round string. The only flat ribbon type material that I know of that would be used in a case like that, is an electric fence product that has small wire woven into it. Also, down in the botom left corner, there is a black box that I dont know the identity of, but it has the same green materal rolled up infront of it that appears to be linking the bottom strand to that stake. I also wonder if that may be the power source. I know it takes very little power to supply a fence. Entire pastures can be powered by a car battery for quite a while. A fence that small only running a few hours at a time wouldn't require much of a power source. I also have read about a couple who did a four wheeler trip from canada to mexico (funded by the maker of the bikes they were on) and they discussed having a fence like that, so they are out there.