Have you cleaned this area up for the pic? Were there leaves or pieces of leaves on the ground? If there was nothing on the ground, that eliminates rabbits and cutworms...but not deer..deer can jump a 7' fence easily, and it's interesting that they seem to be chopped off at the same height, which also suggests deer..coons knock things over when eating them, and ground hogs eat right down to soil level..what part of the country are you in? you may have other things that will eat beans, too.