I had a really big problem with slugs last year, and when I say really big, I mean the slugs were huge! They multiplied quickly and pretty soon it was an invasion. Shortly after, I began to notice these raised rows under my beds in the front and realized that either moles or voles had moved in. Now I was hoping they weren't voles cause they can eat the roots of a tree in no time, whereas moles are there to eat grubs and other things of that nature. The benefit of having moles move in? Within 2 weeks my slugs were gone, which meant they were moles, and because my terrier tried to unearth them on a regular basis, they soon moved out. So without having to do anything, all of my problems were solved!