Environmental watering elevates chytrid infection probability in frogs

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Abstract
Prolonged drought associated with climate change is a global threat to amphibians. Environmental watering could limit declines but may worsen the amphibian disease chytridiomycosis which thrives in wet conditions. We aimed to discover how environmental water and chytrid interact to influence the survival of the endangered frog Pseudophryne bibronii in southern Australia. We provided water to 20 rooftile refuges at each of five sites, while five other sites remained untreated. Frogs beneath rooftiles and natural refuges were swabbed for chytrid, measured, and individually identified monthly throughout the 2022 and 2023 breeding seasons. We found that adding water to rooftile shelters increased chytrid infection and reduced survival. Chytrid zoospore load was negatively related to recapture probability, and infected frogs had reduced survival and poorer body condition. Chytridiomycosis appears to cause both sublethal and lethal effects in P. bibronii. On the other hand, some P. bibronii appeared to clear themselves of chytrid, possibly related to locally unfavorable environmental conditions for chytrid, or adaptation to resist the disease. Chytrid infection probability was highest in the high rainfall 2022 year, later in the breeding season, increased with soil moisture and with soil pH in 1 year, but was not related to soil temperature. We conclude that creating moist refuges should be avoided in normal and high rainfall years because survival decreases and chytrid infection probability increases. However, it remains critical to repeat our methodology in this and other systems during drought, where increased chytridiomycosis caused by watering may be countered by avoiding desiccation‐related mortality.
Funding Information
  • Australia and Pacific Science Foundation (APSF20024)

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