I've now gotten 2 of the tree rats with the Squirrel gun I described earlier, just not quite the way I had in mind.
It turns out that if you lean the 4 in barrel against the fence, with peanut butter dabbed in the inside, the rodents will go to such extremes to get it that they will fall down the barrel, and be unable to escape. At this point, you may do with them what you will: Transport them to Siberia, cook them and eat them*, or whatever.
If you put the bottom of the pipe into a 5-gallon bucket of water, you just need to dispose of the bodies. Fitting them with little concrete overshoes and tossing them into the municipal park pond where they can "sleep with the crawdads" is probably more dramatic than is really necessary.
*I bagged an urban squirrel once, and in my familys best hilbilly tradition, cooked it. That old saw about "you are what you eat" is truer than you think. Woods squirrels are a tasty treat. Urban squirrels that feed in the trash cans, taste like it.