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The first case of Bearded Vulture mortality potentially associated with pentobarbital intoxication 

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Pentobarbital is a pharmaceutical drug commonly used for domestic animals’ euthanasia. In Spain, a Bearded Vulture (Gypaetus barbatus) who died of electrocution tested positive for pentobarbital drugs in the toxicological analyses. The intoxication might not have killed the bird directly but could have affected its equilibrium and reflexes concluded the authors of a recently published study led by Spanish researchers.  

Immature Bearded Vulture © Nello Petito

Pentobarbital intoxication, what is its impact on Bearded Vultures? 

Bearded Vultures are obligate scavengers that do not hunt for prey and feed mainly on bones. Carrion of domestic animals available in the countryside is, thus, an essential food source for these vultures. By feeding on domestic animals, Bearded Vultures are exposed to veterinary drugs and NSAIDs (Nonsteroidal Anti-inflammatory Drugs) that can compromise their survival.  

Barbiturate drugs, such as pentobarbital, are commonly used for euthanising domestic animals. Previously published studies have proved that these toxic compounds can cause lethal poisoning in different species of scavenging birds and mammals once they feed from euthanised animals. It’s the case of another scientific paper, published in 2021, that collected 3280 samples of suspected wildlife and domestic animal poisoning cases in Spain, from 2004 to 2020.  Barbiturate intoxication was seen in 3.4% and over 90% corresponded to pentobarbital intoxication. The authors found out that “avian scavengers were most frequently affected by barbiturate intoxication (n = 36), especially Eurasian Griffon Vultures (Gyps fulvus) (n = 28)”.

The first case of Bearded Vulture mortality potentially associated with pentobarbital intoxication 

A Bearded Vulture was found dead in Northern Spain with external lesions consistent with electrocution. After analysing the bird’s gastric content and liver for toxic substances, researchers detected pentobarbital at a concentration of 37.3 and 0.05 µg/g, respectively.  

“Although the cause of death was electrocution, pentobarbital intoxication likely impaired the equilibrium and reflexes of the individual, possibly causing the bird to contact energised wires that it would not have otherwise. 

 Herrero-Villar M et al. 2023 

These findings emphasise the importance of conducting thorough forensic analyses of wildlife mortality cases and shed light on barbiturate poisoning as an additional risk to the conservation efforts of the Bearded Vulture in Europe. The researchers strongly emphasise the necessity of implementing mitigation measures and control strategies to prevent veterinary drugs from entering the food chain of scavenger birds. By doing so, we can effectively address the additional risk posed to endangered wildlife species. 

Sources: 

  • Herrero-Villar M, Sánchez-Barbudo I, Cardona-Cabrera T, Höfle U, Sánchez-Cano A, Baguena G, Mateo R. Pentobarbital intoxication as a potential underlying cause for electrocution in a bearded vulture. Vet Res Commun. 2023 May 5. https://pubmed.ncbi.nlm.nih.gov/37145336/  

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