Megafire severity, fire frequency and their interactions with habitat affect post-fire responses of small mammal and reptile species

Climate change is driving extreme fires in many ecosystems around the world. There is an urgent need to understand how co-occurring and interacting threats compound megafire impacts on habitats and wildlife. Using repeated surveys after the 2019–20 Australian megafires, we investigated how the abundance and occupancy of five small mammal and reptile species were influenced by fire severity, fire frequency, feral herbivore impacts, three key habitat components (logs, moss, and weeds), and their interactions. We found that fire severity, fire frequency, weeds and logs were the most important factors affecting species abundance and occupancy. Increasing fire severity caused precipitous declines of the threatened broad-toothed rat Mastacomys fuscus and glossy grass skink Pseudemoia rawlinsoni. The impact of fire frequency depended on environmental covariates. High fire frequency led to low abundance of the water skink Eulamprus tympanum and M. fuscus if there were no logs. However, both species increased with fire frequency if logs were abundant, implying that logs can ameliorate negative impacts of frequent fire. The threatened Eulamprus kosciuskoi needed fewer than two fires in the past 80 years as well as high moss cover to achieve high abundance. Two threatened alpine skinks, E. kosciuskoi and P. cryodroma, declined with increasing weed cover. Our study highlights that elucidating interactions between fire and habitat attributes helps to characterise wildfire refuges. Countering the expected impacts of repeated megafires globally will likely require increased protection of refuges from frequent burning, supplementing shelter such as logs where scarce, and mitigating co-occurring and compounding threats.