Anticoagulant rodenticide exposure and toxicosis in bald eagles (Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos) in the United States

PLoS One. 2021 Apr 7;16(4):e0246134. doi: 10.1371/journal.pone.0246134. eCollection 2021.

Abstract

Raptors, including eagles, are geographically widespread and sit atop the food chain, thereby serving an important role in maintaining ecosystem balance. After facing population declines associated with exposure to organochlorine insecticides such as dichlorodiphenyltrichloroethane (DDT), bald eagles (Haliaeetus leucocephalus) have recovered from the brink of extinction. However, both bald and golden eagles (Aquila chrysaetos) are exposed to a variety of other toxic compounds in the environment that could have population impacts. Few studies have focused on anticoagulant rodenticide (AR) exposure in eagles. Therefore, the purpose of this study was to determine the types of ARs that eagles are exposed to in the USA and better define the extent of toxicosis (i.e., fatal illness due to compound exposure). Diagnostic case records from bald and golden eagles submitted to the Southeastern Cooperative Wildlife Disease Study (University of Georgia) 2014 through 2018 were reviewed. Overall, 303 eagles were examined, and the livers from 116 bald eagles and 17 golden eagles were tested for ARs. The percentage of AR exposure (i.e., detectable levels but not associated with mortality) in eagles was high; ARs were detected in 109 (82%) eagles, including 96 (83%) bald eagles and 13 (77%) golden eagles. Anticoagulant rodenticide toxicosis was determined to be the cause of mortality in 12 (4%) of the 303 eagles examined, including 11 bald eagles and 1 golden eagle. Six different AR compounds were detected in these eagles, with brodifacoum and bromadiolone most frequently detected (81% and 25% of eagles tested, respectively). These results suggest that some ARs, most notably brodifacoum, are widespread in the environment and are commonly consumed by eagles. This highlights the need for research to understand the pathways of AR exposure in eagles, which may help inform policy and regulatory actions to mitigate AR exposure risk.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Hydroxycoumarins / adverse effects*
  • Animals
  • Anticoagulants / adverse effects*
  • Bird Diseases* / chemically induced
  • Bird Diseases* / metabolism
  • Bird Diseases* / pathology
  • Eagles / metabolism*
  • Ecosystem
  • Liver / metabolism
  • Liver / pathology
  • Rodenticides / adverse effects*
  • United States

Substances

  • 4-Hydroxycoumarins
  • Anticoagulants
  • Rodenticides
  • bromfenacoum
  • bromadiolone

Grants and funding

We are grateful for funding provided by member state wildlife management agencies of SCWDS in Alabama, Arkansas, Florida, Georgia, Kentucky, Kansas, Louisiana, Maryland, Mississippi, Missouri, Nebraska, North Carolina, Oklahoma, Pennsylvania, South Carolina, Tennessee, Virginia, and West Virginia provided by the Federal Aid to Wildlife Restoration Act (50 Stat.917). Further, we thank our partnering federal agencies, including the United States Fish and Wildlife Service National Wildlife Refuge System, United States Department of Interior (F15PX01848) and the United States Geological Survey Ecosystems Mission Area, United States Department of Interior (G18AC00319). The funders had no role in study design, data collection and data analysis, decision to publish, or preparation of the manuscript.