This seems to be what's been barking my tree. She's been out on her balcony at night, and sees the rats in the trees. They've completely stripped one large branch, eating inner bark, and the branch looks like it was chisel-sculpted. Well, I was talking about taking out some of the big branches that were shading the driveway, anyway... However, the damage to the tree is starting to get substantial. Then I was in the garage and found they're eating cardboard boxes. I had some old boxes full of kitchen stuff (not food, just things like canning jars, etc.), and they were gnawing holes in them. That's when I realized I had to do something.
So I got a new metabolic rat poison, over at Orchard Supply. It's stunningly expensive, but it smells delicious, and it's geared to shutting down certain rodent metabolic pathways so that they gradually decline and die. Says it's safe around kids and pets (provided they're not rodents) and won't cause secondary poisoning if, say, your cat eats a dying mouse. Says that it also doesn't cause bait aversion, as it works so gradually the rats don't associate it with the yummy kibbles they're eating. It's certainly attractive, because I caught Hobbes trying to pick up and eat a pellet that had fallen out of the tray I put in the rose jungle. "Hey! You spit that out right now!" (No, I don't fully trust that it has no effect on cats. But it certainly says something about why I don't want to put out conventional poison.) I'm supposed to start seeing results in around a week. Hopefully, with yummy rat chow out as an alternative, my tree will survive that long. And it will take down the population before they get so out of hand that they try to invade the house, cats or no.