Abstract
Containment is a realistic goal in invasive species management. In this study, we developed a protocol for establishing a containment plan for an alien snail, Helix aspersa (Cornu aspersum), using government occurrence records, i.e., presence/absence. To establish a containment plan, we need to predict occurrences strictly because the containment plan would not be effective if there were mistakes. We used occurrence records for the target species for 4 years and selected areas where the species was absent for 4 years as absence records to report the presence/absence record accurately. We established a statistical model to explain the conditions in the current distribution range, and then we predicted the probability of presence in neighboring regions, including the current distribution range. We also constructed a map to support establishing a containment plan. The results showed that there was a low probability of absence in the northern portion of the current distribution range. This type of map enables land managers to establish a practical plan to contain the target species. Our ideas are useful for both establishing a containment plan and the use of monitoring records.
