MadSci Network: Zoology |
This sounds like a mound made by a prairie dog. These animals are more common further west but might be there. You can find out more about them in any encyclopedia, or in some websites such as this one or this site. Burrowing animals help prairies by turning over the soil and carrying materials underground that help build soil. In addition they help water and air to enter the soil to help roots grow. You might take turns watching the hole to see if you can see this active critter.
Try the links in the MadSci Library for more information on Zoology.