Why Do Snails and Slugs Come
Out at Night?

Answer:

During the day snails and slugs often cluster together in such damp places as underneath stones and rotten logs. Because their soft bodies are susceptible to drying out (this is especially true of slugs without shells). They emerge only when conditions are suitable — after a rain or at night, when the air is cooler and much more humid at ground level.

Water loss is a special problem during certain seasons. Before winter sets in, a snail secretes a double layer of mucus over the opening to its shell; the mucus hardens and reduces water loss. Many types of snails hibernate in this state. Conversely, in hot, dry places snails may not come out of their shells during summer.