I live in the Pacific Northwest and the last month or two I have started seeing Gopher activity underneath my garbage cans. The cans sit on soil patch at the end of my fence. After I observed this I also started to see two more mounds.

I am not sure what this could be. I noticed they had pushed up some soil near the foundation walls, I recall pouring used cooking oil in that spot so I am not sure if that is what attracted them. I have since disposed of used cooking oil elsewhere.

I also had a crawlspace inspector show me a couple of pictures where there have been holes dug under the footing of the foundation and inside the crawlspace. He said they are rodents but didn't give me specifics. So now I am wondering if I need to try poison peanuts, traps, call pest control? What is the best method. I am sure there is no solution like an ant bait which will systematically wipe out colonies. Any suggestions? Mothballs in the crawlspace or around the foundation perhaps?