What makes small dirt mounds in grass?

Small dirt mounds in grass are often created by various burrowing animals, such as earthworms, ants, or small rodents like voles and moles. These creatures dig into the soil, pushing dirt to the surface as they create tunnels or nests. Additionally, insects like beetles or certain types of ants can also contribute to these mounds. The mounds can also be a sign of soil aeration and healthy ecosystems, as these organisms help improve soil structure.