Rethinking Microbial Interventions: The Limits of Probiotics and Alternative Strategies in Amphibian Conservation

ABSTRACT Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis , is one of the main drivers of global amphibian declines. Among the different mitigation strategies proposed, probiotic bioaugmentation—introducing antifungal bacteria to the amphibian skin microbiome—has received considerable attention. Early laboratory and semi‐natural experiments showed promising results, raising expectations that probiotics could be used as a conservation tool in the wild. However, outcomes from subsequent studies have been highly variable, and field‐based applications have often shown limited, short‐lived or context‐dependent effects. In this essay, we critically re‐evaluate the general applicability of probiotic bioaugmentation for controlling chytridiomycosis in natural amphibian populations. We synthesize current evidence and organize the discussion around seven key limitations, grouped into biological, technical and practical dimensions. These include the high specificity and complexity of amphibian skin microbiomes, the evolutionary potential and strain‐level variability of B. dendrobatidis , ecological risks associated with introducing non‐native bacteria, difficulties in selecting effective probiotic strains, inconsistent performance under natural environmental conditions, major logistical constraints, and challenges related to scalability and long‐term sustainability. For each limitation, we briefly discuss alternative or complementary approaches, such as working with native microbial communities, habitat‐based management, postbiotics, integration with host immune responses, predictive modeling, and the promotion of natural microbial antagonists. We argue that, under current conditions, probiotics should still be regarded as an experimental and highly context‐dependent strategy rather than a robust, broadly applicable conservation tool. Overall, effective mitigation of chytridiomycosis is likely to require integrative approaches that combine microbiome research with ecological realism, careful risk assessment, and practical feasibility, rather than relying on probiotics as a standalone solution.