Do the risks of egg cannibalism and desiccation influence the choice of oviposition sites in the land snail Arianta arbustorum?



Laboratory tests were conducted to examine whether egg-laying Arianta arbustorum prevents egg cannibalism in its offspring by the choice of oviposition sites. Arianta arbustorum did not react to the presence of conspecific eggs when starting to oviposit, thus exposing its eggs to the risk of between-batch cannibalism. Snails preferred to oviposit in soil of higher moisture content even at high air humidity, reducing the risks of later egg desiccation and within-batch cannibalism. Both the types of oviposition sites chosen and their spatial distribution, as observed in 11 natural populations of A. arbustorum near Uppsala, Sweden, suggest that abiotic factors, such as a permanently moist microhabitat, may exert a stronger selection pressure on the oviposition-site choice than does between-batch egg cannibalism. As a result, the dispersion of egg batches observed in the field mainly reflects the spatial heterogeneity of habitats.