We've been bothered by chipmunks for several years with two well established burrows next to the house. A ground squirrel also took up residence in a flower bed. After trying biologic and chemical repelling products to no noticeable improvement we opted for solar powered repellers. After about a week with the Pest Repeller Ultimate near a large burrow I saw fresh digging in a raised planting bed about 50' away. After moving a unit there the digging stopped. Entrance holes that were closed up elsewhere have stayed closed, so I believe Pest Repeller Ultimate units are working. We see chipmunks and the occasional ground squirrel on our property but more often heading elsewhere.
I realized seeds under the bird feeder was mainly what they come for, so I am taking the feeders down for a while. The solar system needs good full sun to go 24 hours. They can be a little annoying hearing them when near open windows etc. Overall a good product.