Mucus trail following and optimal foraging in the carnivorous land snail Haplotrema concavum.

Abstract

Haplotrema concavum follows the mucus trails of potential gastropod prey species. Laboratory experiments tested Haplotrema following behavior for four prey species, Strobilops labyrinthica, Zonitoides arboreus, Discus catskillensis, and juvenile Succinea ovalis. Haplotrema exhibited greater following behavior when Discus or Succinea trails were encountered than when Zonitoides trails were met, which was greater than the response to Strobilops trails. The four species were ranked according to characteristic costs and benefits associated with an optimal foraging model. Costs were measured in terms of searching and handling time, estimated by speed and shell thickness respectively. Of the four species, Discus crawled significantly slower than the other species. Succinea was eaten directly through the aperture, rather than after a hole was eaten in the shell, like the others, of which, Discus and Strobilops had thicker shells than Zonitoides. Benefits were measured in terms of dry body weight and preference. Succinea had the greatest body weight and was the most likely to be eaten first in preference tests.