Density and subsurface burrowing of a desert-dwelling land snail, Helminthoglypta greggi, in the western Mohave Desert

摘要

This paper reports on the subsurface burrowing of the desert-dwelling land snail Helminthoglypta greggi in the western Mohave Desert. By excavating into the soil layer, we found that the majority of live snails were burrowed into the soil beneath rocks as well as shrubs, and in both disturbed and undisturbed areas. Live snails were found as deep as 50 cm in the soil layer, and shells as deep as 55 cm. Densities averaged 4.3 live snails per square meter of surface area and 10.1 snails per cubic meter of excavated soil. When these densities are multiplied by a conservative habitat estimate, these snails may number in the millions. Burrowing into the soil layer during wet winter periods allows these snails to escape lethally high temperatures in summer, lethally low temperatures in winter, and desiccation in all seasons. The significance of these findings is twofold. First, it is essential that soil sampling be included in surveys for other Helminthoglypta, as well as for other land snails inhabiting arid environments, or their population number, occupancy, and habitat breadth may be underestimated. Second, like H. greggi, it may be that other species of land snails have been considered rare simply because of inadequate sampling and incomplete understanding of the nature and extent of their habitat use.