Improving a removal model for evaluating density changes in a widespread invasive species

Abstract

Invasive species pose a significant threat to native ecosystems. Effective management of invasive species requires accurate abundance estimates through time, particularly at large spatial scales. Traditional methods of abundance estimation from management data, such as camera trap studies and harvest data, face challenges due to variations in sampling protocols and effort standardization. We propose an extension to a previously calibrated removal model by integrating into an Integrated Population Model (IPM) and incorporating multiple removal techniques. The model utilizes management and land cover data, both of which are readily available in many invasive species systems. We evaluate the model with a simulation study, then apply it to management data on wild pigs (Sus scrofa). Simulations showed that the model performs well across a wide range of densities and population trajectories. Density estimates were the most biased when effort and density were low and sharpshooting or fixed wing aircraft were used to conduct removals. We discuss the advantages and limitations of using removal models for invasive species management, how the model performs with respect to previous removal modeling efforts, how performance might be improved through changes to data management practices, and the models potential to inform decision-making processes for invasive species management. Data availabilityThe data for this manuscript is available from Dryad (http://datadryad.org/share/gFz3ClanB-8yPB5lQ1x-dl1JqI07CP3SX92P-9UyfaU). The code for this manuscript will is available from Zenodo (10.5281/zenodo.15784366).