Our yard is getting areas of soft ground where it feels like you could sink in. Kind of like there could be a tunnel underneath the surface. We figured the problem is either moles or gophers. But in reading up on them, we are not finding any mounds of dirt that fit the description of what moles and gophers produce. We live outside of Houston and have St. Augustine grass. Any ideas? If it is moles or gophers, do you have any recommendations for how to get rid of them?