[user1007]

I would refresh the bait.

As for the bite marks on the garbage can lid? If your sure they are from a rat and not a possum or raccoon?

Does the City, County or State have a rat abatement program that will step in to help you. Sometimes you just need to ask.

I live in a nice section of Chicago but rats are a problem. Believe it or not one of their major sources of foods has to do with the turds that get cranked out from the designer dog food tiny little rat like, car wash sponge dogs the princesses all have (You would have to glue 12 together to get a real dog). People don't feel compelled to pick up after their pets here, or even curb them so the street sweepers can move you know what away. The City is aggressive about rodent control.

 

[PAbugman]

Rodenticides should be changed in order to keep fresh, whether or not they are visibly ruined.

In a dry environ they should be changed every 3-4 months, more frequently in damp environs.

 

[WillK]

I figured as much, just wanted to check.

I don't really have any idea what was chewing on the garbage can lid, the hole might have been enough for a possum to get through and I know at a previous house we had in the next suburb over we had a possum family living in the garage.

I don't really think the rats are around right now at our house, but the wife gets those fears pretty easy. Our cat is a pretty good indicator of if anything is really going on, although at the moment the weather is nice so we have open windows and the cat has a bird obsession.

 

[PAbugman]

Generally speaking, when multiple rats are in the area, you will know it by their fecal material, many chewings, sightings. They get braver as time goes on; young ones get careless. keep the bait fresh and stay alert. Sounds like you are on top of things.