Effect of Light and Substratum Structural Complexity on Microhabitat Selection by the Snail Helix

Terrestrial snails choose their microhabitat according to a number of environmental factors. We evaluated the effect of light intensity and substratum complexity on microhabitat preference of the terrestrial snail Helix aspersa using a multi-factorial design. The snails were offered two levels of light intensity and two types of structural complexity, hence 16 treatments in total were used: 12 in which choice was offered and 4 in which no choice was offered. The snails preferred ambient light over dim light, regardless of substratum complexity, and complex over smooth substrata, regardless of light intensity. The level of one factor did not affect the response to the other. Thus, the results revealed a preference for microhabitats with greater light intensity and that were structurally complex, and a rejection of dimly lit microhabitats with smooth substrates.