Brown Tree Snakes: Methods and Approaches for Control

Clark, Larry; Clark, C. F.; Siers, Shane R.

doi:10.1201/9781315157078-7

Cited by 17 publications

(24 citation statements)

References 50 publications

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“…The drastic difference in detectability by trapping and/or visual surveys underscores the importance of preventing accidental introduction of brown treesnakes to other islands (e.g., Saipan, Rota, Tinian, Hawaii) where large prey are abundant. Decreased activity and response to the lures and baits associated with brown treesnake control tools (Clark, Savarie, Shivik, Breck, & Dorr, ; Clark et al., ; Siers et al., in press) following feeding on large prey items will make eradication of a new incipient population an even more daunting prospect. Strategies for increasing detectability of brown treesnakes in prey‐rich areas may include suppression of large prey (e.g., Christy et al., and Gragg et al., ) to increase the level of foraging behavior, reduce the frequency of submergent behavior, and enhance the relative attractiveness of lures and baits.…”

Section: Discussionmentioning

confidence: 99%

“…Strategies for increasing detectability of brown treesnakes in prey‐rich areas may include suppression of large prey (e.g., Christy et al., and Gragg et al., ) to increase the level of foraging behavior, reduce the frequency of submergent behavior, and enhance the relative attractiveness of lures and baits. Cycles of foraging quiescence should also be accounted for in timing of applications of control tools such as aerial delivery of toxic baits (Clark et al., ; Dorr, Clark, & Savarie, ; Siers et al., in press), to ensure that the availability of baits exceeds the five‐ to seven‐day period during which recently fed snakes may not be foraging.…”

Section: Discussionmentioning

confidence: 99%

“…Results of this invasion included the extirpation or extinction of nearly the entire native forest avifauna (Savidge, ; Wiles, Bart, Beck, & Aguon, ), with cascading ecological and economic consequences (e.g., Perry & Morton, ; Rogers, Hille Ris Lambers, Miller, & Tewksbury, ; Rogers et al., ), and impacts on domestic poultry production, tourism, and human health (Fritts & McCoid, ; Fritts, McCoid, & Haddock, ; Rodda & Savidge, ). Because Guam is a major hub for commercial and household goods throughout the Pacific, economic impacts are increased by the cost of developing, testing, and implementing tools and strategies to reduce brown treesnake abundance and preventing accidental transportation of brown treesnakes to other Pacific islands such as Saipan, Rota, Tinian, and Hawai'i (Clark, Clark, & Siers, ; Engeman & Vice, ; Pimentel, Lach, Zuniga, & Morrison, ).…”

Section: Introductionmentioning

confidence: 99%

“…These factors have also been indicated to influence brown treesnake movement characteristics (Santana‐Bendix, ; Tobin, Sugihara, Pochop, & Linnell, ; Siers, Reed, & Savidge, ; Christy et al., ). If brown treesnakes decrease movement and foraging during digestion, this will have implications for the effectiveness of various control tools that typically rely either on visual detection by human searchers or response of foraging snakes to lures or baits (e.g., Christy et al., ; Clark et al., ; Engeman & Vice, ; Lardner et al., ; Tyrell et al., ).…”

Section: Introductionmentioning

confidence: 99%

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Behavioral differences following ingestion of large meals and consequences for management of a harmful invasive snake: A field experiment

Siers

Adams

Reed

2018

Ecology and Evolution

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Many snakes are uniquely adapted to ingest large prey at infrequent intervals. Digestion of large prey is metabolically and aerobically costly, and large prey boluses can impair snake locomotion, increasing vulnerability to predation. Cessation of foraging and use of refugia with microclimates facilitating digestion are expected to be strategies employed by free‐ranging snakes to cope with the demands of digestion while minimizing risk of predation. However, empirical observations of such submergent behavior from field experiments are limited. The brown treesnake (Serpentes: Colubridae: Boiga irregularis) is a nocturnal, arboreal, colubrid snake that was accidentally introduced to the island of Guam, with ecologically and economically costly consequences. Because tools for brown treesnake damage prevention generally rely on snakes being visible or responding to lures or baits while foraging, cessation of foraging activities after feeding would complicate management. We sought to characterize differences in brown treesnake activity, movement, habitat use, and detectability following feeding of large meals (rodents 33% of the snake's unfed body mass) via radio telemetry, trapping, and visual surveys. Compared to unfed snakes, snakes in the feeding treatment group showed drastic decreases in hourly and nightly activity rates, differences in refuge height and microhabitat type, and a marked decrease in detectability by trapping and visual surveys. Depression of activity lasted approximately 5–7 days, a period that corresponds to previous studies of brown treesnake digestion and cycles of detectability. Our results indicate that management strategies for invasive brown treesnakes need to account for cycles of unavailability and underscore the importance of preventing spread of brown treesnakes to new environments where large prey are abundant and periods of cryptic behavior are likely to be frequent. Characterization of postfeeding behavior changes provides a richer understanding of snake ecology and foraging models for species that consume large prey.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Behavioral differences following ingestion of large meals and consequences for management of a harmful invasive snake: A field experiment

Siers

Adams

Reed

2018

Ecology and Evolution

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“…A variety of control efforts have been implemented to reduce or eliminate BTS on Guam and to prevent its dispersal to other areas (Clark, Clark, & Siers, ; Engbring & Fritts, ; Rodda & Savidge, ). Baited traps are a primary method of control, and improving trap success will likewise promote BTS management.…”

Section: Discussionmentioning

confidence: 99%

Genomic pedigree reconstruction identifies predictors of mating and reproductive success in an invasive vertebrate

Levine

Douglas

Adams

et al. 2019

Ecology and Evolution

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The persistence of an invasive species is influenced by its reproductive ecology, and a successful control program must operate on this premise. However, the reproductive ecology of invasive species may be enigmatic due to factors that also limit their management, such as cryptic coloration and behavior. We explored the mating and reproductive ecology of the invasive Brown Treesnake (BTS: Boiga irregularis) by reconstructing a multigenerational genomic pedigree based on 654 single nucleotide polymorphisms for a geographically closed population established in 2004 on Guam (N = 426). The pedigree allowed annual estimates of individual mating and reproductive success to be inferred for snakes in the study population over a 14‐year period. We then employed generalized linear mixed models to gauge how well phenotypic and genomic data could predict sex‐specific annual mating and reproductive success. Average snout–vent length (SVL), average body condition index (BCI), and trappability were significantly related to annual mating success for males, with average SVL also related to annual mating success for females. Male and female annual reproductive success was positively affected by SVL, BCI, and trappability. Surprisingly, the degree to which individuals were inbred had no effect on annual mating or reproductive success. When juxtaposed with current control methods, these results indicate that baited traps, a common interdiction tool, may target fecund BTS in some regards but not others. Our study emphasizes the importance of reproductive ecology as a focus for improving BTS control and promotes genomic pedigree reconstruction for such an endeavor in this invasive species and others.

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Predation thresholds for reintroduction of native avifauna following suppression of invasive Brown Treesnakes on Guam

McElderry

Paxton

Nguyen

et al. 2022

Ecological Applications

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The brown treesnake (BTS) (Boiga irregularis) invasion on Guåhan (in English, Guam) led to the extirpation of nearly all native forest birds. In recent years, methods have been developed to reduce BTS abundance on a landscape scale. To help assess the prospects for the successful reintroduction of native birds to Guåhan following BTS suppression, we modeled bird population persistence based on their life history characteristics and relative sensitivity to BTS predation. We constructed individual-based models and simulated BTS predation in hypothetical founding populations for each of seven candidate bird species. We represented BTS predation risk in two steps: risk of being encountered and risk of mortality if encountered. We link encounter risk from the bird's perspective to snake contact rates at camera traps with live animal lures, the most direct practical means of estimating BTS predation risk. Our simulations support the well-documented fact that Guåhan's birds cannot persist with an uncontrolled population of BTS but do indicate that bird persistence in Guåhan's forests is possible with suppression short of total eradication. We estimate threshold BTS contact rates would need to be below 0.0002-0.0006 snake contacts per bird per night for these birds to persist on the landscape, which translates to an annual encounter probability of 0.07-0.20. We simulated the effects of snake-proof nest boxes for Sihek (Todiramphus cinnamominus) and Såli (Aplonis opaca), but the benefits were small relative to the overall variation in contact rate thresholds among species. This variation among focal bird species in sustainable predation levels can be used to prioritize species for reintroduction in a BTS-suppressed landscape, but variation among these species is narrow relative to the required reduction from current BTS levels, which may be four orders of magnitude higher (>0.18). Our modeling indicates that the required predation thresholds may need to be lower than have yet been demonstrated with current BTS

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Brown Tree Snakes: Methods and Approaches for Control

Cited by 17 publications

References 50 publications

Behavioral differences following ingestion of large meals and consequences for management of a harmful invasive snake: A field experiment

Behavioral differences following ingestion of large meals and consequences for management of a harmful invasive snake: A field experiment

Genomic pedigree reconstruction identifies predictors of mating and reproductive success in an invasive vertebrate

Predation thresholds for reintroduction of native avifauna following suppression of invasive Brown Treesnakes on Guam

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