Below are additional photos that show the lack of dirt from excavation.

Holes in a yard are a challenge to diagnose. We generally try to do a process of elimination based on the size of the holes, if mounds of soil are present, if tunnels are present, etc. This chart is helpful to try and hone in on the culprit https://naturalresources.extension.iastate.edu/wildlife/diagnosing-holes-yard

We cannot say for sure but we think you may be dealing with voles. They are a type of mouse in the landscape that feeds on the roots of trees, shrubs, perennials, etc. They make silver dollar sized holes where they can access tunnels underground. Perhaps you can sprinkle some flour or ground limestone in the area and look for tracks. You may also want to set some mouse traps in an out of the way area.  Cover with a plastic pail or box to prevent tampering by other wildlife or children. https://extension.umd.edu/resource/voles

Marian

Thanks for the prompt reply.  However, while the decision tree provided a logical path it did not help.  There is a clear hole; the hole is bigger than a quarter, at least at the surface;it is smaller than a softball and golf ball (I could not lose a golf ball in the hole; it would sink into the hole a bit).  Thus, it appears it would be a vole.  However, there are no runaways.  There are raised mounds of grass throughout the yard.  I can stick my finger through the mound and find a tunnel.  I suspect a mole.  I wish it were voles.  Voles would be easier to trap.  

To add to the above, at this time there are no mounds of dirt.  In the spring there were mounds of dirt.  Could this be an indicator.  Would you expect mounds in the spring and not the fall?

As plants die back for the winter and expose more soil surface, you may find many more holes. This year we had the 17-year cicadas emerge and they made millions of small holes (you mention many of a half inch in your first question). Their holes can be seen as a type of aeration. Other holes and humps were likely made as other animals of all types (skunks, raccoons, squirrels, birds, moles etc) used them for food. If you find raised ridges, tamp them down with your foot so grass roots stay in contact with soil. Watch for any that pop up again- that could be a sign of an active mole. Live with it if you can, there are usually not that many per acre and they are considered beneficial. Their feeding on soil invertebrates is more noticeable when we've had a lot of rain, as the food source (worms, grubs etc.) rise in the soil profile.

You later mention holes more the size of a golf ball, which is closer to 2". This does sound more like rodent activity, seeking shelter in a warmer winter location near your foundation. Setting some snaps traps can take down your populations.

Christine