Bushfire alters the gut microbiome in endangered Kangaroo Island echidnas (Tachyglossus aculeatus multiaculeatus)

Kangaroo Island experienced extensive bushfires in December 2019 and January 2020, affecting almost half of the island. This impacted several threatened species including the Kangaroo Island echidnas (Tachyglossus aculeatus multiaculeatus). Echidnas can often survive fires, however, changes in soil chemistry and food availability raises questions about the impact on echidna gut health and foraging behaviours. Due to local participation in the citizen science project, EchidnaCSI, echidna scats were collected before and after the fires to directly assess how fire affects their gut microbiomes. Metabarcoding of scat microbiota (n = 13) revealed substantial changes in bacterial composition of echidna faeces post-bushfire when compared to samples collected prior to bushfires. Before the fires, echidna gut microbiomes were more variable and contained mostly soil-associated bacteria, whereas post-fire samples shifted to uniform bacterial communities consisting of lactic acid and gut commensal bacteria. Interestingly, changes were observed in scats collected in both burnt and unburnt regions of the island, suggesting echidnas are foraging between these areas. This is the first study to document changes in gut microbiome of any mammal following bushfires. More work is needed to investigate if the gut bacterial communities continue to change as areas recover from fires.