Targeting eradication of introduced watersnakes using integral projection models

Abstract

AbstractProjection models are frequently used to identify and evaluate management actions to control or eradicate non‐native species. Integral projection models (IPMs) are an appealing option for many taxa because IPMs can model vital rates as a function of continuous variables, like size, without discretizing into a few classes. Despite their strengths, IPMs have yet to see widespread use in invasive species management. Here, we used an IPM to evaluate management actions for an introduced population of common watersnakes (Nerodia sipedon) recently established in California, USA, where they pose a threat to many highly imperiled native fauna. We developed the IPM using data on the survival, growth and fecundity of native and non‐native populations of N. sipedon to identify management targets that would facilitate its eradication. Population growth of N. sipedon was most sensitive to the growth and survival of snakes during their first year, when they grow from approximately 180 mm snout–vent length (SVL) to 350 mm, providing a clear target for eradication efforts. The IPM also provided finer resolution life‐history information for targeting eradication than a simple size class‐based matrix model. Simulated eradication effort showed funnel trapping, which targets all but the smallest and largest snakes, was more effective at decreasing population growth than hand capture focused on snakes >400 mm SVL. Our study highlights the value of IPMs for targeting eradication of introduced or invasive species, and we argue for wider adoption of these models for evaluating management actions.