Waking hours: nightly forays
Hatchlings are immediately mobile, but remain concealed during the day. Slugs are nocturnal and become active only between dusk and dawn.
The lifespan, which generally ranges from one to six years, varies according to species and according to habitat. Life cycles may be annual, confined to one year, or biennial, stretching over two years, or even plurennial, lasting beyond two years.
Also, an outdoor slug faces more hazards from predators than a greenhouse slug.
As slugs move, they secrete slime, which protects its sensitive ventral, or belly, area from harm by coating its path. These silvery, iridescent trails also guide slugs back and forth between favored food sources in their nightly forays. Additionally, many potential predators are disinclined to struggle with slippery prey that also have a slimy taste.
During dry, hot spells, slugs slather themselves with mucus and then aestivate (Latin: aestivus, "summer-like") by immobilizing themselves through burial in mulch or soil or through attachment to or under rocks and stones.