We use a similar idea for possums in the orchard. 55 gal. drum half full of water. Stack blocks like steps and toss a few rotten fruit in the drum. Possums jump in for the fruit, eventually can"t tread water anymore and that"s that. Use a manure fork to pick them out in the AM, add more fruit in the evening and your back in business.
Mice and rats are not a problem here, these twins keep things neat and tidy!