Geology topics

Alacia Welch

Publications and source records attributed to Alacia Welch.

3 recordsLinked to original sources

USGS2026

Behavioral shifts mask the success of legislation and outreach for endangered species recovery

A fundamental challenge in conservation is assessing the efficacy of recovery actions to optimize endangered species management. Considerable recent attention has focused on effective measures to counter the endangerment of avian scavengers, which have declined worldwide, primarily due to poisoning. One iconic example is efforts to recover the critically endangered California condor ( Gymnogyps californianus ), whose leading cause of death is poisoning from ingesting lead-based ammunition in carcasses. Despite enormous resources expended in California, USA, including implementation of public outreach campaigns and two legislative bans on lead ammunition, lead-related mortality of condors has increased. Here we show that two types of behavioral shifts explain the observed increases in condor lead exposure: wilder foraging and ranging by condors and increased shooting of wild pigs ( Sus scrofa ) by humans. After accounting for these trends, we show that both lead ammunition bans and public outreach efforts have significantly reduced condor blood lead levels in California, lowering mortality. Our analyses uncover a dynamic in which changing ecological conditions mask the true efficacy of legislation and outreach. Given rapid global change, such dynamics are likely operating in many settings, underscoring the importance of comprehensive evaluations of recovery actions, which can be obscured by shifting behaviors and threats.

Baja California, California↗

USGS2022

Collateral damage: Anticoagulant rodenticides pose threats to California condors

Anticoagulant rodenticides (ARs) are widespread environmental contaminants that pose risks to scavenging birds because they routinely occur within their prey and can cause secondary poisoning. However, little is known about AR exposure in one of the rarest avian scavengers in the world, the California condor ( Gymnogyps californianus ). We assessed AR exposure in California condors and surrogate turkey vultures ( Cathartes aura ) to gauge potential hazard to a proposed future condor flock by determining how application rate and environmental factors influence exposure. Additionally, we examined whether ARs might be correlated with prolonged blood clotting time and potential mortality in condors. Only second-generation ARs (SGARs) were detected, and exposure was detected in all condor flocks. Liver AR residues were detected in 42% of the condors (27 of 65) and 93% of the turkey vultures (66 of 71). Although concentrations were generally low (<10 ng/g ww), 48% of the California condors and 64% of the turkey vultures exposed to ARs exceeded the 5% probability of exhibiting signs of toxicosis (>20 ng/g ww), and 10% and 13% exceeded the 20% probability of exhibiting signs toxicosis (>80 ng/g ww). There was evidence of prolonged blood clotting time in 16% of the free-flying condors. For condors, there was a relationship between the interaction of AR exposure index (legal use across regions where condors existed) and precipitation, and the probability of detecting ARs in liver. Exposure to ARs may complicate recovery efforts of condor populations within their current range and in the soon to be established northern California experimental population. Continued monitoring of AR exposure using plasma blood clotting assays and residue analysis would allow for an improved understanding of their hazard to condors, particularly if paired with recent movement data that could elucidate exposure sources on the landscape occupied by this endangered species.

California↗

USGS2018

Critically assessing the utility of portable lead analyzers for wildlife conservation

Lead (Pb) exposure in wildlife is a widespread management and conservation concern. Quantitative determination of Pb concentrations in wildlife tissues is the foundation for estimating exposure and risk. Development of low‐cost, portable instruments has improved access and cost‐effectiveness of determining Pb concentrations in blood samples, while also facilitating the ability for wildlife researchers to conduct near real‐time Pb testing. However, these instruments, which use anodic stripping voltammetry (ASV) methodology, may produce an analytical bias in wildlife‐blood Pb concentrations. Additionally, their simplicity invites use without appropriate quality‐assurance–quality‐control measures. Together, these factors can reduce data quality and hamper the ability to evaluate it, raising concerns about use of these instruments to inform important conservation issues. We document the extent to which this bias is addressed in the wildlife toxicology literature, develop quantitative approaches for correcting the bias, and provide recommendations to ensure robust data quality when using these instruments. Of the 25 studies we reviewed that referenced ASV use for determining Pb exposure in wildlife, only 32% acknowledged the existence of bias from the instrument. Importantly, another 20% of the studies actually reported ASV and spectroscopic‐based results together without acknowledging their lack of equivalence. Using a multispecies data set of avian blood Pb concentrations, we found that ASV‐based estimates of paired blood Pb concentrations were 30–38% lower than those from standard spectrometric‐based methods. We provide regression equations based on this analysis of 453 blood samples to allow users of ASV instruments to adjust Pb concentrations to spectrometric‐equivalent values, and propose a series of guidelines to follow when using these instruments to improve data validity.

Wildlife Society Bulletin↗