Do Native Rodents Prey on Land Snails? An Experimental and Quantitative Study in Hokkaido, Japan

Predator-prey interaction is one of the most important and pervasive pressures in the ecology and evolution of prey species. However, accurate description of the food web is sometimes extremely difficult as there are many predator-prey interactions in the wild are obscure. Recent studies have reported that two closely related land snails, Karaftohelix editha and K. gainesi, on Hokkaido Island, Japan, were diversified due to predation, probably by carabid beetles. However, it is unclear 1) whether native rodents prey upon land snails on Hokkaido Island, and 2) how frequently land snails are preyed upon by rodents in this region, although it has been reported that several species of rodents are predators of land snails in many regions. Thus, we investigated these issues in this study by captive feeding trials and field observations. No rodent species other than the Siberian chipmunk, Tamias sibiricus, were found to prey upon land snails around the research site on Hokkaido Island. In addition, the population density of T. sibiricus was lower than those of other rodent species, and it has been reported that T. sibiricus is omnivorous and preys upon snails considerably less than on other food sources. Overall, these findings suggest that T. sibiricus is not an important predator of Karaftohelix land snails in Hokkaido.