Abstract
BackgroundInvasive reptiles pose a serious threat to global biodiversity, but early detection of individuals in an incipient population is often hindered by their cryptic nature, sporadic movements, and variation among individuals. Little is known about the mechanisms that affect the movement of these species, which limits our understanding of their dispersal. Our aim was to determine whether translocation or small-scale landscape features affect movement patterns of brown treesnakes (Boiga irregularis), a destructive invasive predator on the island of Guam.MethodsWe conducted a field experiment to compare the movements of resident (control) snakes to those of snakes translocated from forests and urban areas into new urban habitats. We developed a Bayesian hierarchical model to analyze snake movement mechanisms and account for attributes unique to invasive reptiles by incorporating multiple behavioral states and individual heterogeneity in movement parameters.ResultsWe did not observe strong differences in mechanistic movement parameters (turning angle or step length) among experimental treatment groups. We found some evidence that translocated snakes from both forests and urban areas made longer movements than resident snakes, but variation among individuals within treatment groups weakened this effect. Snakes translocated from forests moved more frequently from pavement than those translocated from urban areas. Snakes translocated from urban areas moved less frequently from buildings than resident snakes. Resident snakes had high individual heterogeneity in movement probability.ConclusionsOur approach to modeling movement improved our understanding of invasive reptile dispersal by allowing us to examine the mechanisms that influence their movement. We also demonstrated the importance of accounting for individual heterogeneity in population-level analyses, especially when management goals involve eradication of an invasive species.
Highlights
Invasive reptiles pose a serious threat to global biodiversity, but early detection of individuals in an incipient population is often hindered by their cryptic nature, sporadic movements, and variation among individuals
Identifying invasion pathways and preventing translocation are the first lines of defense, but for individuals that evade these efforts, early detection and rapid response are considered the most efficient and cost-effective ways to prevent the spread of invasive species [2,3,4]
We developed a Bayesian hierarchical model to account for individual heterogeneity in snake behavior while using treatment-level parameters to test these hypotheses regarding the effect of translocation and small-scale landscape features on brown treesnake movement
Summary
Invasive reptiles pose a serious threat to global biodiversity, but early detection of individuals in an incipient population is often hindered by their cryptic nature, sporadic movements, and variation among individuals. Studies with the goal of informing eradication efforts of invasive species must consider individual heterogeneity to ensure coverage of all individuals within a population, allowing managers to determine how heavily they can rely on population-level averages of movement parameters. We use the term “individual heterogeneity” in this work to refer to the differences in movement parameters among individuals in a population This term can be used to describe heterogeneity in a single individual’s movements over time, we focus on among-individual variation because the applications of this work involve the management of invasive reptile populations
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