Selective land snail predation by the spiny mouse, acomys cahirinus, in nahal oren, mt. Carmel, Israel

Microclimatic differences between the south-facing slope and the north-facing slope of the Lower Nahal Oren, Mt. Carmel, Israel result in a dramatic biological divergence. The south-facing slope harbors predominantly African representatives, including the spiny mouse, Acomys cahirinus. The northfacing slope harbors predominantly European taxa, including the prosobranch land snail Pomatias olivieri. Here we show that predation by Acomys on European Pomatias exceeds the proportion of Pomatias shells among the large land snail fauna at the microsite. The ratios of consumed to unconsumed Pomatias were approximately 4: I and 7: I in the north- and south-facing slopes, respectively. In all other land snail species, the consumed constituted at most 2/3 of the unconsumed. Remarkably, the selective predation of Acomys on Pomatias is significantly higher on the warmer and drier south-facing slope. We hypothesize that natural selection led to an adaptive behavioral predatorprey relationship at the microsite.