Thus slugs may be active during the day after a cooling shower as long as the temperatures decline or remain steady. Development ceases below 5 C. Slugs can withstand slight freezing temperatures although their tendency to take shelter in cold weather protects them from freezing. Slugs try to escape from temperatures higher than 21 C. Slugs are also sensitive to air currents. Gentle breezes elicit a positive response in which the slug turns toward the source and extends its antennae. As the breezes become more brisk, the slugs turn away from the source evidently to escape dehydration.
Slugs can withstand brief periods of immersion under water, although they drown after several hours.
Sciomyzid flies and nematodes also parasitize slugs. In addition, slugs are preyed upon by omnivorous slugs such as the spotted garden slug. Dry weather may kill up to 90 percent of slug eggs and young per year. Metaldehyde baits have been shown to attract slugs up to 1 meter away. Thus in dry weather, metaldehyde is more effective.