What is digging in my yard ?!

Mole mounds will be volcano or cone shaped. They can be small or very large. The presence of mole mounds typically will also have visible raised tunnels and/or soft spongy areas in your lawn. Moles will not leave the entrance to their mounds/tunnels open. In sandy soil, one mole can easily dig 20' in one hour! 

Pocket gopher mounds will sometimes have a crescent shape with a visible dirt plug towards the bare side of the crescent. Gophers will not leave the entrance to their mound/tunnel open. Gopher mounds will not always take this shape and may also look similar to mole mounds. One gopher can create several mounds in one day!

Both moles and pocket gophers will and do travel above ground to cross over concrete and hard surfaces. This image is of a mole in North Texas that exited the ground on the right side of the image and went back into the soil on the left side.

Squirrels make tiny holes, about the size of a quarter, and will be open about 1-2" deep. There are no mounds and they are often scattered in lawns and flower beds.

Will leave open holes into underground burrows with dirt mounds, typically 4 - 10" in diameter.

Opossums do not dig holes but they will move into one created by other large animals

They dig above ground for a protein source food below. Extreme damage may be caused by raccoons, armadillos and skunks that root would look like this.

Inverted cone shaped damage, about 3" in diameter, is typical of armadillos digging in lawns and mulch beds. Skunks can be similar but this type of activity is more likely armadillo damage. This inverted cone shape is similar to the damage done by squirrels but much larger,  50% larger in diameter and depth.

While many insects (beetles and ants, for example) dig holes, they are not as obvious as the cicada killer wasp. Their holes are easy to spot due to their large size, 1-1.5" in diameter. They will often have dirt  mounds at the entrance of an opening.

Insanely large holes or crop circles is definitely from aliens. Ghostbusters are retired so you're on your own solving that problem!

Gophers & moles will chew thru lawn irrigation pipes. This is ~1" hole that a gopher chewed. Location was Southlake.

Gopher checking on us while doing a job. Location was Colleyville. 

This is a typical tunnel caused by gophers & moles. Larger tunnels is common of gophers due to their larger size.  

Location was Bartonville.