Species-specific gut microbiome responses to rodenticide exposure: restructuring in greenfinches but stability in pigeons

Background Rodent eradication on oceanic islands is essential for the conservation of endemic species. Although anticoagulant rodenticides (ARs) are widely used for rodent control, their potential impacts on non-target wildlife require careful evaluation. We focused on the gut microbiome as a non-invasive indicator of AR exposure. Here, we administered ARs to Oriental greenfinches ( Chloris sinica minor ) and rock dove ( Columba livia ) as surrogate species for the critically endangered Bonin greenfinch ( Chloris kittlitzi ) and red-headed wood pigeon ( Columba janthina nitens ) to evaluate gut microbiome responses to ARs exposure. Results In Oriental greenfinches, AR administration altered gut microbial community composition, increased α diversity, and enriched several bile acid-associated bacteria, including Bacteroides, Prevotella , and Collinsella . In contrast, neither first- nor second-generation AR administration induced significant changes in gut microbial diversity or community composition in rock doves. Conclusion Our findings demonstrate species-specific gut microbiome responses to AR exposure. The consistent enrichment of bile acid-associated bacteria in Oriental greenfinches suggests that alteration in bile acid metabolism may represent a characteristic response to AR exposure. Gut microbiome analysis may therefore provide a useful non-invasive tool for evaluating the impacts of rodenticides on endangered island birds.