And just what do you think the green matter than deer eat contains? Answer---Protein! When they eat a lot of alfalfa and other similar moist, green crops it is very normal for them to leave big clumps of droppings like this. When there is a heavy rain it can do exactly what the OP picture looks like and sometimes if they are also eating other materials like browse it can be clumps where you can see the start of where pellets were being formed. Obviously none of us can be 100% positive of the OP picture because we didn't see the individual animal go poop, LOL, but with decades in the woods some of us have a pretty good idea after having seen many different droppings at various times of the year. In the winter when deer are on a hard, woody browse diet they definitely produce hard, individual pellets as compared to when they are eating very moist, soft crops during the warm months. Some fescue and grasses they consume will only have 5 to 9 percent protein content while a crop of alfalfa may have upwards of 20%. I've watched many a deer in the late summer feeding on moist alfalfa and soybeans and they are literally drooling green out of their mouths and about the same comes out the rearend to varying degrees after it's digested. As another member stated, generally the bigger the clump the bigger the deer was that left it behind.