There are many creatures that will create holes in lawns. As with all areas of pest control, it’s essential to know your target pest. Methods, materials, traps, baits, etc. vary widely from species to species. In this case it is important to know if the holes are openings that lead to underground burrows (e.g., moles, pocket gophers, or voles) or if they are simply excavated shallow hollows in soil or turfgrass. It’s also important to know if the holes are quite round or somewhat irregular in shape.
If the holes are connected to underground burrows and there are no mounds of soil covering them, you may have Norway rats, chipmunks, or other type of ground squirrel. Rodent activity is even more likely in the vicinity of bird feeders. Voles also create holes, but these are usually smaller, approximately 3/4- to 1-inch in diameter. However, when vole numbers are high, or if voles are reusing tunnels dug by pocket gophers, the holes can easily be 2 inches in diameter.
If the hole is a shallow hollow, the list of culprits is shortened by the fact that the hole diameter is 2 inches. If the holes occur near water, you may want to consider crayfish. Chipmunks will create a 2-inch-wide hole, usually mounded about 1 inch. Moles create tunnels, but these are always covered by conical mounds. Pocket gophers also make tunnels, but these mounds are large bean-, fan-, or dune-shaped and have a plugged hole. Both moles and gophers live in tightly sealed burrow systems. However, voles are known to co-habit in these tunnels at times. Typically surface feeders, voles will open holes in mole and gopher mounds to gain access to aboveground foods. Also, moles will often create “feeder tunnels” that look like raised ridges in turfgrass and planter beds. If not mounded, the holes may be a squirrel looking for nuts or a raccoon looking for grubs and earthworms.
Resources: (online)
Clemson Extension Home and Garden Information Center
Chipmunks
Inspection Decision Tree