Q.A hole dug on either side of our patio
Started about three weeks ago. I noticed two large piles of soil on either side. Thinking my husband was doing some work, I put the soil into two large buckets for him. I then forgot to mention this to him. To my surprise the next morning the soil had reappeared. On closer inspection, I could see deep holes. The soil had been dug out like a dog would dig, kicking the soil under him to cause a rather high mound. I am worried it could be rats setting up for the winter. I have looked on the internet and it seems foxes and squirrels burrow underground too.
Photographs show mounds so similar to each other, so I cannot determine who has caused this. The holes are neat, no more than 4″ across, but they go deep. We did have a squirrel visit our bird feeder in the summer but have not seen him since. We have also had a fox in the garden at various times too. I would say around six buckets of soil have been excavated so far. If filled in, the holes are back next day. We do love the wildlife in our garden but we are worried they could cause damage or health problems, especially if they are rats.
Any advice would be welcome. Thank you, Chrissy

A 4" hole could indeed be rats. You could get some traps, if you want to DIY, or contact a professional to remove the digger(s).
I would advise against poison. This article has more information: https://www.gardeningknowhow.com/lawn-care/lgen/lawn-and-garden-holes.htm