What Do The Slugs Know That I Do Not?

I put out beer bait tonight for the slugs. There are very, very few out there! I've caught maybe a dozen, and I looked at the usual hangouts- almost none! Where are they? I captured 2,499 of them by the end of  last night- have most of them headed for less hazardous pastures? Is it too cold and windy? Is it going to frost, and they're staying sheltered? It makes me nervous to see a marked change in habits of an animal or group of animals, because they can sense things we cannot. We'll see in the AM.