Agreed, rat traps are SCARY!
We had a bucket trap in the back porch where our Irish setter had his bed, food and water. He had a doggie door to the fenced yard. DH had antifreeze in the bucket trap, so we had it under the porch where the dog couldn't get to it and tip it over.
DH kept checking the trap and never saw any mice in the bucket. After about a month and 1/2 he saw a mouse in the anti-freeze, so he took the bucket to the garage to put the mouse in the garbage there. When he went to scoop out the mouse, he discovered that mice sink in anti-freeze. The one he saw was on top of the pile - he counted 26 mice, but figures there were more of them in there.