The Battle of the Rat rages on. Yesterday, after a few days of thinking the little rodent had deserted our yard for greener pastures, we spotted him again just as we were heading out for the evening. So when we got home, Brian once again baited the snap trap and set it out in the garden. And when he went out this morning to check it, he found in it...a bird. (A dead one, fortunately, since a live but horribly injured one would be an even more hideous scenario.)
This was the first time our battle against the rat had claimed an innocent victim, and Brian felt really terrible about it. We'd tried to avoid hurting any harmless critters by putting the trap out only at night and inside the garden boundaries, so that any large or non-nocturnal animals would be unlikely to encounter it. But birds are up with the sun and we're not, especially on Saturdays in summertime, so it became clear that so long as this trap was in a spot where birds could reach it, there was no way to ensure that they wouldn't become collateral damage.
So Brian came up with a new plan: we'd use the rat's own cunning against him. The whole reason he's been a problem for us is that he's small enough, and wily enough, to slip through the chicken-wire fence into our garden, so he built a small chicken-wire cage to enclose the trap. It's similar to the squirrel-blocking cages he built to enclose our eggplants (although if, as we now suspect, it was actually the rat that stole the eggplants last year, rather than a misguided squirrel, then I guess it won't actually keep him out. Fortunately, he doesn't seem to have shown any interest in them so far.) With the trap safely contained inside the cage, the wily rat will still have access to it, but the birds won't. Although we know the rat's small enough to slip through chicken wire (since we've seen him do it), Brian cut a couple of slightly larger holes in the mesh to make sure he has no problem getting in (but not, if all goes well, out).
Another advantage of enclosing the trap in a cage like this is that we can now leave it out during the daytime without fear of harming birds or other wildlife, rather than having to set it out each night and bring it in each morning. We've set it out in the same corner of the garden where it was before; if we left it out in the open there was a slight risk the groundhog or some other larger critter might manage to tip the cage over. Brian weighted it down with a rock to keep the wind from blowing it over, and now we play the waiting game. The modified trap may or may not catch the rat, but at least we can be sure it won't catch anything we don't want caught.