Evidence of Persistence of Two Small, Sympatric Threatened Mammals (Dasyuridae) Following a Major Flood Event

Large-scale, extreme flood events can potentially cause catastrophic declines in floodplain-dwelling species, especially small terrestrial mammals. We undertook surveys to assess the status of two species of threatened Dasyurid mammals (Giles' Planigale Planigale gilesi and Fat-tailed Dunnart Sminthopsis crassicaudata) to see if they were persisting in a region of northwest Victoria 12 months after a large-scale flood event. We tested three possible detection techniques: live trapping using Elliott traps, camera traps with drift fences and thermal imaging transects. Surveys revealed that sympatric House Mice (Mus musculus) were in very high abundance following the flood. Both target species were detected using camera traps only, although at a very low rate. This demonstrates the limited availability of an effective survey technique for these cryptic species. These surveys resulted in the threatened Giles' Planigale being detected for the first time in 11 years in Victoria. There are two likely scenarios for the persistence of native mammals: in situ survival either by taking refuge in trees within small cavities for the duration of the flood event or on small island refuges nearby, or ex situ survival whereby animals perished in the flood event and individuals recolonised our sites from larger islands that remained dry throughout the flood. Further research is needed to understand the mechanisms by which small, ground-dwelling mammals can survive large-scale flooding events and the potential for competition with the invasive House Mouse following these disturbances.