Invasive brown treesnakes (Boiga irregularis) move short distances and have small activity areas in a high prey environment

Abstract

Animal movements reflect temporal and spatial availability of resources as well as when, where, and how individuals access such resources. To test these relationships for a predatory reptile, we quantified the effects of prey abundance on the spatial ecology of invasive brown treesnakes (Boiga irregularis) on Guam. Five months after toxicant-mediated suppression of a brown treesnake population, we simultaneously used visual encounter surveys to generate relative rodent abundance and radiotelemetry of snakes to document movements of surviving snakes. After snake suppression, encounter rates for small mammals increased 22-fold and brown treesnakes had smaller mean daily movement distances (24 ± 13 m/day, $$\overline{x }$$ x ¯ ± SD) and activity areas (5.47 ± 5 ha) than all previous observations. Additionally, snakes frequenting forest edges, where our small mammal encounters were the highest, had smaller mean daily movement distances and three-dimensional activity volumes compared to those within the forest interior. Collectively, these results suggest that reduced movements by snakes were in part a response to increased prey availability. The impact of prey availability on snake movement may be a management consideration when attempting to control cryptic invasive species using tools that rely on movement of the target species to be effective.

Spatial ecology to strengthen invasive snake management on islands

“…This reduced our final sample size, and possibly skewed the results obtained in some comparisons, mainly regarding sexes. Finally, several ecological parameters can also influence animal spatial behavior (for instance density, prey and shelter availability, degree of anthropization, habitat type 12 , 35 , 87 ). We are however highly confident that our results provide robust knowledge on home range, phenology and activity patterns of L. californiae, which can be used to improve control action designs for the whole island of Gran Canaria and possibly elsewhere.…”