Frogs, fire, and fungus: The effects of prescribed fire on frog occupancy and health in a biodiversity hotspot

Abstract

The global amphibian extinction crisis results from many threats, including anthropogenic climate change, modified fire regimes, and disease. Identifying the effects of these processes is crucial for frog conservation, especially in regions where species experience ongoing prescribed fire and chytridiomycosis. The interactive effects of these threats on frog communities have received limited research focus. Using multiple detection methods in eucalypt forests of southern Australia, we evaluated changes in frog site occupancy, body condition, and chytrid infection across a time‐since‐fire gradient exceeding 20 years. Our analyses concern our most commonly detected frog, the threatened Pseudophryne bibronii . Using multivariate modeling, we evaluated occupancy and detection probability of P. bibronii and accounted for climatic, demographic, disease, and microhabitat characteristics that may affect frog responses to previous fire. Site occupancy, body condition, and chytrid infection did not change with time since fire. Frog body condition declined during warm temperatures, particularly in summer, at hillslope sites (monitoring sites outside of low‐lying breeding habitat), while increased rainfall during autumn at breeding drainages improved condition. At hillslope sites, subadult frogs were more likely to be infected than were adults, suggesting an ontogenetic shift in infection probability. During the autumn reproductive period, higher temperatures were associated with increased infection prevalence in breeding drainages and lower prevalence at hillslope sites. Chytrid infection was associated with greater body condition, potentially reflecting the improved capacity of larger frogs to withstand infection. Infection intensity varied considerably, and we observed clearance of infection in two recaptured individuals. Our findings reflect sampling during La Niña conditions; therefore, future studies should evaluate the interactive effects of fire, climate, and disease on frog health and survival during drought. This research increases our understanding of the synergistic consequences of anthropogenic fire regimes and climate for frog health and disease risk and provides recommendations for landscape management and further research that will enhance biodiversity conservation.