Identify burrow owner

[nightshade]

It does sound like a Rat. Can you locate its food source, as that is the primary reason for them hanging around. I saw one yesterday climbing a vertical garage wall, they are very accomplished climbers.
Using the garden and moving things around will make the Rat nervous (you do need to keep this up) and incline it to move on. I started putting pebbles in the burrow, Not to block it but just to make it a less desirable residence due to the disturbance.

[rawoak]

You may be sure it's more than one. There is a saying "for ever rat you see there are 7 you don't ," but a large pinch of salt is needed with that. How ever I stopped worrying about the a long time age since you are never far from rats wherever you live. Your method sounds fine to me the rats will smell the bate and eat thought the plastic. (don't forget to dispose of it.)