Sunday, August 18, 2013

Oh, rats

After all the trouble we went to building a groundhog-proof fence for our garden so that we could peacefully coexist with our resident groundhog, it appears that we now have a new and even more cunning garden pest: Rattus norwegicus, the common brown rat. Or at least, a common brown rat.

The first sign of it came on Friday, when Brian brought in a zucchini from the garden that had clearly been gnawed on by something. We were puzzled, because we were pretty sure we'd finally managed to build a fence the groundhog couldn't penetrate, and in any case, if he'd eaten it he'd probably have eaten the whole thing. But what else could possibly have gotten in? A squirrel? Surely they wouldn't be interested in zucchini, would they? Baffled, we cut off the bitten parts and set aside the rest, figuring the only thing we could really do was keep an eye on the garden and see if we could spot the culprit.

The answer to the puzzle became clear yesterday, as we were sitting in the back yard taking a break from the task of transferring the big pile of concrete chunks to a less obtrusive spot in the back corner of the yard. (Side note: The pieces that were pebble-sized, or not too much larger, got spread along the gap between our rhubarb bed and the main garden area, on top of a layer of weed barrier. We also threw in the remainder of the gravel left over from the patio project and the assorted rocks we'd pulled out of the ground when we planted our plum trees way back in March. We're hoping that this lot will, if not keep the weeds out entirely, at least deter them enough that we don't have to do more than an occasional weeding back there.)

Anyway, as we sat on the grassy bank, trying to work up the energy to get back to our task, Brian suddenly pointed and said, "Look at that." And there, perched right next to the groundhog hole, as bold as you please, was an unmistakeable furry grey critter. It ducked out of sight as soon as we moved, but it didn't take long for it to prove that it was, in fact, the culprit in the zucchini-gnawing incident: next time we looked, we saw one of the zucchini plants moving back and forth, even though there was no wind. And when we headed for it, a furry grey shape bolted straight out of the garden, squeezing right past the gate, and whisked down the groundhog hole.

Our reaction to this new intruder was kind of interesting. Naturally, we were somewhat concerned about having it on the premises at all, since rats, unlike groundhogs, can carry diseases that affect humans. And naturally, we were also annoyed about the loss of our veggies (including the other half of the chewed-on zucchini, which we threw away just to be on the safe side). But we also both found ourselves feeling rather offended to see this upstart intruding on the territory of the groundhog, which we had come to see as an authorized, accepted resident of our property. I actually felt kind of ticked off on the groundhog's behalf: "Who does this rat think he is, anyway, trying to use the groundhog's hole as if it were his own?" Brian, by contrast, felt annoyed at the groundhog: "Hey, what are you doing letting this rat use your burrow? We allow you to stay on our property, but we never said you could have house guests!"

So I had a look around on the Internet for information on rats as garden pests and what to do about them. I found one article on the Organic Gardening site that mentioned that rats supposedly dislike the smell of mint, so I decided as a first step to spray the plants with a solution of Dr. Bronner's Peppermint Oil Soap and see if that deterred the little rodent. Brian also shimmed out the garden gate, which had become a little loose-fitting near the bottom—still plenty tight enough to keep out a groundhog, but easily wide enough for a rat to squeeze through. However, within half an hour after applying both of these remedies, we took another look out the window and saw the zucchini plant wiggling again. Then, as we watched, the rat took off and squeezed straight through the fence, chicken wire and all, not even bothering to go near the gate. So far, the score was Rat 2, Amy and Brian 0.

So we decided it was time to bring out the big guns. Two separate articles I found on rat control (one from the University of Illinois and one from UC Davis) confirmed that no repellant, whether smell-based or sound-based, will deter rats for very long, so if we wanted this thing out of our yard, pretty much our only option was to kill it outright. Based on the article, a trap seemed to be the best choice; unlike poison, it would pose no hazard to humans and most other critters, and it would also ensure that the rat died in a spot where we could find it and dispose of it, rather than leaving a rotting (and, eventually, stinking) carcass in some hard-to-reach spot. The article advised against using the humane type of trap that catches the animal alive, since you really don't want to release a disease-carrying critter into the wild, so we figured we'd have to go for the traditional snap trap, which would (we hoped) kill the rat as quickly and painlessly as possible.

At Lowe's, we found two types of rat traps: the old-fashioned wooden type, with a metal pin on a spring, for two dollars, and a fancier plastic one called a Tomcat trap for five dollars. We opted for the latter, as it looked like it would be much easier to bait and set without injuring ourselves, and also less likely to inadvertently trap some harmless animal just passing by, such as a bird or a stray cat. The trap was in two pieces: a hinged set of plastic jaws, and a removable cup for the bait. Setting it was indeed quite easy: Brian filled the little cup with peanut butter, snapped it into place, carried the whole trap out to the garden, placed it against the side of one of the beds, and stepped on it to pop it open. Unfortunately, I can't give the trap equally high marks for effectiveness. When Brian went out to check on it this morning, he found the trap had been sprung, turned upside down, and dragged to another part of the garden, and the cup that had held the peanut butter was not only empty but completely gone. Rat 3, Amy and Brian 0.

However, Brian is not one to give up that easily. Since the main part of the trap was still intact, he went down into the shop and made a couple of modifications to it. First, he rigged up a board with a short length of dowel to stick up through the hole where the cup used to go. Since we're using peanut butter, we don't really need a cup for it; we can just smear it on the dowel. Then he screwed the body of the trap itself onto the board, which should make harder for the rat to flip over. The trap is a little more difficult to set now—you have to hold it open with one hand while using the other to spread peanut butter on the dowel—but it is definitely heavier and more stable, and it no longer flips over when you set it off. (Brian actually managed to close it on himself at one point, but fortunately it wasn't fully open to start with, so it didn't cause any real damage. I just hope that from a fully cocked and loaded position, it's powerful enough to kill the rat right away.)

We're waiting until nightfall to deploy the modified trap, since rats are more active at night, while birds and other critters we'd rather not harm are less so. If the rat manages to get the bait out of this one without setting it off, I'm not calling an exterminator; I'm calling a science lab, because this rat is obviously some sort of rodent genius who needs to be captured and studied.
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