Contact rates with nesting birds before and after invasive snake removal: estimating the effects of trap-based control

By

Yackel Adams, Amy A.
Nafus, Melia
Klug, Page E
Lardner, Björn
Mazurek, M.J.
Savidge, Julie
Reed, Robert

Type

Article

Date of Publication

2019

Original Publication

NeoBiota : advancing research on alien species and biological invasions

Volume

49

Pages

1-17

Subjects

Avian recovery , Biological invasions , brown treesnakes , Control , Guam , restoration

Contributed by

Pensoft Publishers

Language

English

Published by

Sophia, Bulgaria Pensoft Publishers

Identifiers

DOI: https://doi.org/10.3897/neobiota.49.35592

 

Abstract

Invasive predators are responsible for almost 60% of all vertebrate extinctions worldwide with the most vulnerable faunas occurring on islands. The brown treesnake (Boigairregularis) is a notorious invasive predator that caused the extirpation or extinction of most native forest birds on Guam. The success of avian reintroduction efforts on Guam will depend on whether snake-control techniques sufficiently reduce contact rates between brown treesnakes and reintroduced birds. Mouse-lure traps can successfully reduce brown treesnake populations at local scales. Over a 22-week period both with and without active snake removal, we evaluated snake-trap contact rates for mouse- and bird-lure traps. Bird-lure traps served as a proxy for reintroduced nesting birds. Overall, mouse-lure traps caught more snakes per trap night than did bird-lure traps. However, cameras revealed that bird-lure traps had a snake contact rate almost 15 times greater than the number of successfully captured snakes. Snakes that entered bird-lure traps tended to be larger and in better body condition and were mostly captured in bird-lure traps, despite numerous adjacent mouse-lure traps. Traps placed along grid edges caught more snakes than interior traps, suggesting continuous immigration into the trapping grid within which bird-lure traps were located. Contact between snakes and bird-lure traps was equivalent before and after snake removal, suggesting mouse-lure traps did not adequately reduce the density of snakes that posed a risk to birds, at least at the timescale of this project. This study provides evidence that some snakes exhibit prey selectivity for live birds over live mouse lures. Reliance on a single control tool and lure may be inadequate for support of avian reintroductions and could lead to unintended harvest-driven trait changes of this invasive predator.