The Decline of Australian Heath Frogs and Summary of Current Threats

The southern and northern heath frogs (Litoria watsoni and Litoria littlejohni) are sister treefrog species experiencing an enigmatic decline across large parts of their range. Their naturally low abundance, uncommon habit of breeding sporadically throughout the year, and restriction to high elevations (> 100 m), make these species some of the most poorly recorded frogs in Australia. This natural rarity makes detecting a decline difficult, and the heath frogs’ need for conservation action has only recently been realized as recorded sightings have substantially declined in the past decade. Like many Australian frogs, heath frog declines have likely been driven by the amphibian fungal pathogen, Batrachochytrium dendrobatidis, which causes the disease, chytridiomycosis. Little testing has been done for these species’ susceptibility to chytrid, but the pathogen’s impact is inferred through the pattern of decline that has occurred across a broad distribution within protected habitats. In addition to disease, the devastating 2019/20 bushfires burnt significant portions of habitat, and longwall mining is causing further habitat degradation. These declines are particularly concerning given disjunct species distributions and low genetic diversity. Fortunately, both frog species are now receiving considerable conservation attention, in the hopes that they can be protected in the wild.