The predatory snail Euglandina rosea (Férussac, 1821) is native to the southeastern U.S.A. and has been widely introduced as an attempted biological control agent for agricultural pest gastropods, often targeting the giant African snail Achatina fulica Bowdich, 1822. However, E. rosea may impact native land snails rather than A. fulica, particularly in Hawaii. Laboratory prey preference trials for E. rosea were conducted using three prey taxa, including the endemic endangered Oahu tree snail Achatinella lila Pilsbry, 1914, the giant African snail A. fulica, and the introduced Asian trampsnail Bradybaena similaris (Rang, 1831). Trials were conducted in the laboratory on branches of ohia lehua trees, Metrosideros polymorpha, an important habitat component for Hawaiian tree snails. Y-shaped ohia branches were used to simulate tree snail habitat and test E. rosea's ability to track and pursue prey via slime trails on branches, and to evaluate prey choice by offering trails of two different species simultaneously and slime trail vs. water. Euglandina rosea significantly favored branches with slime trails vs. water, choosing the branch with slime trail 90% of the time (P < 0.001). Predatory snails exhibited no significant preference between B. similaris and A. fulica (P = 0.820), or B. similaris and A. lila (P = 0.260). However, E. rosea showed a significant preference for native Achatinella lila over invasive Achatina fulica (P = 0.040), the intended target species of the biological control program.
Hawaiian tree snails