Collateral damage: Anticoagulant rodenticides pose threats to California condors

Garth Herring; Collin A Eagles-Smith; Rachel Wolstenholme; Alacia Welch; Chris West; Barnett A Rattner

doi:10.1016/j.envpol.2022.119925

Collateral damage: Anticoagulant rodenticides pose threats to California condors

Environ Pollut. 2022 Oct 15:311:119925. doi: 10.1016/j.envpol.2022.119925. Epub 2022 Aug 18.

Authors

Garth Herring¹, Collin A Eagles-Smith², Rachel Wolstenholme³, Alacia Welch⁴, Chris West⁵, Barnett A Rattner⁶

Affiliations

¹ U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, 97331, USA.
² U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, 97331, USA. Electronic address: ceagles-smith@usgs.gov.
³ Pinnacles National Park, Paicines, CA, 95043, USA; Current: National Park Service, Interior Regions 8, 9, 10, & 12, San Francisco, CA, 94104, USA.
⁴ Pinnacles National Park, Paicines, CA, 95043, USA.
⁵ Yurok Tribe Wildlife Department, Klamath, CA, 95548, USA.
⁶ U.S. Geological Survey, Eastern Ecological Science Center, Beltsville, MD, 20705, USA.

PMID: 35988680
DOI: 10.1016/j.envpol.2022.119925

Abstract

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.

Keywords: Anticoagulant rodenticides; Avian scavengers; Blood clotting; Brodifacoum; Bromadiolone; Survival toxicosis; Turkey vulture.

Published by Elsevier Ltd.

MeSH terms

Animals
Anticoagulants / toxicity
Birds
Endangered Species
Falconiformes*
Rodenticides* / toxicity

Substances

Anticoagulants
Rodenticides