I noticed there were a lot of animal skeletons cluttering up the entrance to the fortress, and I realized it was because I had set the dwarves to ignore refuse/remains on the surface. It was bothering me, so I changed that order, and a bunch of dwarves swarmed out to collect all the refuse that had been accumulating up there. But they didn't just gather the stuff at the entrance. They spread out and started picking up stuff all over the map, which quickly led to them getting into fights with nearby agitated wildlife. They were just workers, not prepared for combat, and soon they started getting killed by agitated cow moose and giant chipmunks. After about five of these deaths, I gave up and set them to ignore refuse on the surface again, but more of them are still getting killed as they wander around. I guess the moral of the story is that dwarves should stay underground. It's kind of irritating that however all the wildlife ended up becoming agitated (I think it's because we did too much fishing?), they don't seem to ever stop being agitated.