We have lots of gophers here and they do lots of damage. I started using Euphorbias some years ago when I was told it would repel them. The gophers and voles are gone from the areas I planted the this toxic plant, so 3 years ago I started planting lilies, I could never have them before because of the gophers. I have not lost one of my lovely lilies. The gophers are everywhere else in the yard, but they don't go where the Euphorbia is planted.
They would even open their tunnel right next to a tomato plant and eat the tomatoes and sqaush. Not anymore.
