Testing toxicants and baits to control small invasive lizards

Abstract

Several species of small invasive lizards form high densities in their invaded ranges and threaten native biodiversity in a variety of ways. Little attention has, however, been devoted toward identifying tools to control populations of these lizards for conservation purposes. Some of these invasive lizards or their close relatives consume a variety of sweet food items, either natural or human-made. Thus, we conducted experimental laboratory trials to identify the potential for sweetened solutions, pastes, or fruit products to serve as attractive baits for two invasive lizard species, and we evaluated the potential effectiveness of acetaminophen and alpha-chloralose to serve as toxicants when mixed in such baits. Using paired-choice tests, we identified red baits (as corn syrups, sweetened pastes, or strawberries) as the most effective baits for Anolis carolinensis and white corn syrup as the most effective bait for Hemidactylus frenatus. Bait attractiveness was improved by the addition of vanilla flavoring. We assessed the LD100 of acetaminophen and alpha-chloralose to A. carolinensis, H. frenatus, and Lampropholis delicata by oral application of solutions of known concentration. Acetaminophen proved infeasible for use as a toxicant in sweet baits because of its low aqueous solubility and high concentrations needed to attain lethality; alpha-chloralose was more successful in this regard because of its greater toxicity and smaller quantities needed for use. However, keeping the toxin in suspension remains a problem. Trials combining alpha-chloralose with some of the more effective baits provided some degree of lethality among samples but indicated that further work is required in order to identify the best bait matrix for control projects in a field setting. We recommend next steps to advance development of an effective toxicant+bait system for controlling small invasive lizards that build off our results.