Slugs are common garden inhabitants, often recognized by their soft, elongated bodies and the glistening trails they leave behind. These creatures, which are essentially snails without prominent external shells, are frequently observed after rainfall or during the cooler hours of the evening. What slugs do during the day remains less visible to many observers.
Reasons for Daytime Hiding
Slugs primarily seek shelter during daylight hours due to their acute vulnerability to dehydration, as their soft, moist skin, which lacks a protective outer shell, makes them highly susceptible to water loss through evaporation. Exposure to direct sunlight and dry air can rapidly cause a slug to lose significant body water. Slugs can lose up to 50% of their body weight in water during dry periods.
To maintain their body moisture, they must find cool, damp environments. Additionally, hiding during the day helps slugs avoid various predators that are active in daylight, such as birds, toads, and ground beetles.
Preferred Resting Places
During the day, slugs retreat to locations that offer optimal conditions of dampness, darkness, and coolness. They frequently hide under various natural and artificial structures.
Common hiding spots include under rocks, logs, and thick layers of leaf litter. Dense vegetation, particularly groundcover plants, provides ideal shaded and moist conditions for slugs to rest.
Garden debris, such as discarded boards, unused pots, and even the saucers of potted plants, also serve as favored refuges. Slugs can also burrow into soil crevices or under mulch, seeking the cool, damp conditions beneath the surface.
Nighttime Behaviors
As dusk arrives and temperatures drop, slugs emerge from their daytime retreats to become active. They are primarily nocturnal, conducting most activities under the cover of darkness or during overcast, damp daytime conditions.
Slugs navigate their environment by secreting a layer of mucus from their muscular foot, which acts as a lubricant, allowing them to glide smoothly over various surfaces. This mucus trail also reduces abrasion and helps them find their way back or locate other slugs.
Foraging is a significant nighttime activity, with slugs consuming a wide range of organic matter. Their diet can include decaying plant material, fungi, and various live plants, often leaving irregular holes in leaves and stems. Their feeding habits make them a common concern for gardeners, as they can cause considerable damage to seedlings and mature plants.