Individual heterogeneity influences the effects of translocation on urban dispersal of an invasive reptile

Abstract

Background 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. 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. Methods We 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. Results We 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. Conclusions Our 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.

Spatial ecology to strengthen invasive snake management on islands

“…The overall spatial parameters studied for L. californiae on Gran Canaria showed a wide variation. This disparity may be explained mainly by the effect of individual heterogeneity on spatial behavior, already demonstrated for other invasive snake species 82 . This spatial heterogeneity can be due to individual body condition affecting movement ecology 83 , individual personality influencing exploratory and defensive behaviors 84 or boldness and sociability 85 , as well as dispersive movements (such as may have happened with our individual 010).…”

A hierarchical modelling framework for estimating individual‐ and population‐level reproductive success from movement data

“…The individual level (first stage) of our model is computationally intensive on its own, so the ability to implement it separately (and in parallel) for each individual is crucial to being able to scale the model to estimate population‐level reproductive success. Although only recently introduced to applied ecological statistics (Hooten et al, 2016; McCaslin et al, 2021), recursive Bayes is starting to gain traction in applied studies (Cameron et al, 2021; Eisaguirre et al, 2022; Feuka et al, 2022). Our approach provides another example of its utility in estimating complex, multi‐level ecological models for making both individual‐ and population‐level inference.…”

“…The individual level (first stage) of our model is computationally intensive on its own, so the ability to implement it separately (and in parallel) for each individual is crucial to being able to scale the model to estimate population-level reproductive success. Although only recently introduced to applied ecological statistics (Hooten et al, 2016;McCaslin et al, 2021), recursive Bayes is starting to gain traction in applied studies (Cameron et al, 2021;Eisaguirre et al, 2022;Feuka et al, 2022). Our approach provides another example of its utility in estimating complex, multi-level ecological models for making both F I G U R E 6 Posterior realizations of breeding status z i,t from the Ornstein-Uhlenbeck nest survival model fit to golden eagle data from southcentral Alaska for (top to bottom) a likely midseason failure with an observation of z i,t = 1 in May, a likely late season failure with an observation of z i,t = 1 in June and a likely successful nesting attempt with an observation of z i,t = 1 in May.…”

Multistage hierarchical capture–recapture models

“…that was generalized by Hooten et al (2021), where it was referred to as “prior‐proposal recursive Bayesian” (PPRB) computation. Recursive approaches to fitting certain classes of Bayesian ecological models have been demonstrated (e.g., Feuka et al, 2022; Gerber et al, 2018; Hooten et al, 2016; Leach et al, 2022; McCaslin et al, 2021), but have been less commonly used in Bayesian population modeling using CR data.…”