Hmm, hard to say just by looking at an entry hole. You have quite a few species of burrowing rodents out there, from ground squirrels, to voles to moles to shrews to mice to rats, and several species of each. If you can't get a good look at the actual animals, it might help to narrow down by determining average size of burrow entry hole, and to look for associated sign, such as runs, scat placement, feeding sign, and above ground nests. Meadow voles, for example, make shallow burrows also more noticeable are the above ground runways and nests under clumps of grass. Also soil and moisture helps narrow it down. Prairie vole likes drier, sandier soil, whole meadow vole likes moister soil and lusher growth. Can you mount a game camera on a post near a well used hole?