My guess it that the other posters are correct in saying Armidillo. It does not look like near enough damage to be hogs. Hogs can root up very large areas very quickly and easily.
They look exactly like the holes in my yard. The pressed cone shape of the hole matches the nose of the armadillo as he mashes his snout into his freshly dug hole looking for grubs.
Armadillo (aka possum on a half-shell) for sure. They're probably digging for some tasty grubworms. Around here, when the weather gets dry and the ground gets hard, the 'dillos come into well irrigated lawns and dig those craters everywhere.