That looks like herbivore damage. Deer, rabbits, and ground hogs are possible culprits. I'd first suspect rabbits, since ground hogs would have eaten the neighboring plants as well.

No deer here. I have seen a rabbit make its way into the yard lately but I figured a rabbit would continue eating not just eat one or two. I have also found some of the tops that were cut just laying there

I saw this and new exactly that it was a rabbit. Jon, I read they prefer the young ones that are tender and sweet. Once the beans reach a certain size they aren't as palatable and if the rabbit has other foods nearby, it will leave them alone when they are larger.

bon

My assumption of rabbits above was based upon observations of their feeding habits. Deer or ground hogs would have eaten the whole row, or at least most of it. There wouldn't be any left over bits on the ground. Rabbits browse, sampling a little of everything... and they will often bite something off, then spit it out. They have been doing that to my emerging lily shoots, and have done that to my beans in the past.

Rabbits really love certain things, such as tulips and soybeans. Those they will mow to the ground. For the most part, though, they would rather eat the clover around my garden, than the vegetables in it.

Rabbits got my garbanzo beans last year, and a few yellow beans, but left all the others alone. This year I put collars around the garbanzos until they get a little tougher. I do have chicken wire, and it usually keeps them out, but every once in a while one gets through.