Geology Reports⌕ Search
Home/Archive/USGS

USGS · 70210992

Validating deployment of aerially delivered toxic bait cartridges for control of invasive brown treesnakes

Scott Michael Goetz·Amy A. Yackel Adams·Shane S Siers
View original source ↗Export metadata ↓

Abstract

Aerial application of management tools can provide a cost‐effective means to conserve or control wildlife populations at the landscape scale. Large spatial scales, however, present difficulties when assessing in situ reliability and integrity of the devices themselves. We demonstrate application of a distance‐sampling density estimation approach to assess the performance of a newly developed toxicant bait system for the control of invasive brown treesnakes ( Boiga irregularis ). Bait cartridges were designed to open in flight to expose the toxicant‐laced bait and tangle in the forest canopy via a plastic ribbon component. Following application of 12,686 bait cartridges from an automated aerial delivery system over a 55‐ha site on Guam, USA, we employed distance sampling techniques to evaluate cartridge performance. We performed 22 line‐transect surveys for a total distance of 10.3 km, during which we recorded all observations of unopened bait cartridges, instances in which the ribbon did not remain attached to the cartridge capsule (i.e., ribbon failure), and carcasses of brown treesnakes and nontarget species. Too few undeployed bait cartridges ( n = 6), brown treesnake carcasses ( n = 1), or nontarget carcasses ( n = 0) were observed during surveys to support additional analysis. We detected 299 instances of ribbon failure. Using standard distance‐sampling analyses, we estimate that ribbon failure occurred in 3,376 ± 351 (estimate ± SE; 95% CL = 2,746–4,150) cartridges or 21.6–32.7% of the total applied. Our results demonstrate the utility of distance‐sampling density estimation techniques to validate performance and reliability of aerially applied management tools.

Explore related subjects

Wildlife Society BulletinArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 13.199838554004245° to 13.675344552820276° latitude; 144.57733154296875° to 144.98931884765625° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Scott Michael Goetz, Amy A. Yackel Adams, Shane S Siers. 2020-07-03. Validating deployment of aerially delivered toxic bait cartridges for control of invasive brown treesnakes. https://doi.org/10.1002/wsb.1106

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Considerations for using autonomous recording units to monitor northern bobwhite occupancy at large spatial scales

Northern bobwhites ( Colinus virginianus ) have experienced widespread declines across their range, increasing the need for population monitoring across broad spatial and temporal scales. Yet large-scale monitoring of post-breeding bobwhites remains limited by the time-intensive nature of fall (i.e., autumn) covey counts. Passive acoustic monitoring with autonomous recording units (ARUs) and automatic detection software may help overcome these constraints but requires further study. From 2017 to 2021, we paired in-person observer point counts with ARU surveys during the fall in southern Iowa, USA to 1) evaluate how ARU detections compare to observer detections, 2) assess the accuracy of automatic classification software for covey calls, 3) gauge the influence of weather and ordinal date on detection, and 4) offer best practices for processing ARU acoustic data. We found high correspondence (89.2%) in detection and non-detection outcomes between paired ARU and observer surveys. Across manually processed recordings, 95.7% of covey call detections occurred within a 35-min window (50–15 min before sunrise). Increasing wind speed and cloud cover were associated with reduced detection probabilities. Wind speeds ≥5 m/s resulted in detection probabilities <0.5. The cumulative probability of detecting bobwhites at a site exceeded 0.995 (95% Credible Interval [CrI] = 0.987, 0.999) after 4 survey days when technicians processed the files. Manual processing had the highest mean detection probability (0.75, 95% CrI = 0.66, 0.82) compared with automatic detection software with 2 different confidence thresholds (0.46 [95% CrI = 0.39, 0.53] and 0.45 [95% CrI = 0.36, 0.55]). Automatic detection software allowed for substantially faster processing with relatively few false positives (false positive rate of 0.014 to 0.038). Autonomous recording units coupled with automatic detection software provided a promising alternative to in-person observer point counts of bobwhite covey calls for determining site occupancy and have the potential to greatly increase capacity for landscape-level bobwhite monitoring.

Iowa↗
USGS2026

Developing a low-cost drone-based method for deploying and retrieving autonomous recording units in inaccessible areas

Autonomous Recording Units (ARUs) are increasingly used in research to support passive acoustic monitoring, but deployment in remote or inaccessible locations remains logistically challenging. Traditional manual placement is labor-intensive, time-consuming, potentially hazardous, and often limited to habitat edges, creating sampling biases and restricting spatial coverage. To address placement limitations in wetland systems, we developed and field-tested a low-cost, lightweight floating platform paired with a drone-based deployment and retrieval system. The drone-deployable ARU platform, constructed from inexpensive, off-the-shelf materials (~US $21 per unit), weighed ~560 g and was mounted with an ARU (AudioMoth) at ~1.2 m above water. The platform was designed for stability, portability, and compliance with Federal Aviation Administration Part 107 regulations. Field trials were conducted across 50 operations in various types of historical rice-field impoundments along the South Carolina coast, which provide critical habitat for secretive marsh birds such as rails (e.g ., Rallus, Laterallus , and Porzana ) and bitterns (e.g ., Botaurus and Ixobrychus ). All 50 deployments and retrievals were successful, demonstrating the robustness of the method under diverse hydrologic and vegetative conditions. Deployment times were significantly shorter than retrieval times (median 6 vs. 9 min), with retrieval requiring greater precision for hook engagement. Operation times scaled predictably with distance: deployment increased by 0.93 min/100 m (R 2 = 0.94) and retrieval by 1.17 min/100 m (R 2 = 0.95). No platform damage or displacement was observed, as emergent vegetation was likely providing natural anchoring. Our approach offers an affordable and effective solution for expanding ARU coverage in large, inaccessible wetlands, reducing sampling bias and enhancing biodiversity monitoring. With continued advances in drone payload capacity, battery endurance, and beyond-visual-line-of-sight flight regulations, our workflow could be adapted for deploying multi-sensor platforms (e.g., ARUs, eDNA samplers, water and air quality sensors, plant sample collectors, insect traps, and trail cameras) to support integrated biodiversity monitoring in challenging landscapes worldwide.

South Carollina↗