Habitat Distribution in the Desert Snail Trochoidea seetzenii

Abstract

what are the factors that influence the density distribution, among habitats, of the desert snail, Trochoidea seetzenii. This was done by examining the relationship between individual movement, reproductive success and density distribution of a population in two habitats. We studied individual movement in two adjacent habitats, the wadi and the lower slope of the same watershed. The overall experimental design entailed: a) enclosed plots in which the original density distribution was maintained, b) enclosed plots in which all the snails from the wadi were transfered to the slope, c) enclosed plots in which all the snails from the slope were transferred to the wadi, d) unfenced control plots with no limitations on direction of snail movement. We found that in the winter, after the first heavy rains, snails moved from the wadi to the slope until snail density was similar in the two habitats. In the late rainy period we found the opposite trend in movement, resulting in higher density in the wadi relative to the slope. This directional movement was found in the undisturbed as well as in the manipulated plots. We suggest that the temporal changes in the density distribution of T. seetzenii are mainly the effect of the snails moving between habitats so that they seem to maximize reproduction in winters and survival in summers.