The occurrence of the Broad-toothed Rat Mastacomys fuscus in relation to feral Horse impacts

Feral Horse (Equus caballus) impacts in northern Kosciuszko National Park, New South Wales, Australia are directly occurring in habitat of the nationally threatened Broad-toothed Rat (Mastacomys fuscus). This species is endemic primarily to the mountain regions of south-eastern mainland Australia and Tasmania, with a disjunct population at Barrington Tops. The Broad-toothed Rat's preferred habitat is being increasingly impacted by browsing and trampling associated with the expansion of feral horse populations. This study surveyed 180 sites supporting preferred habitat for this species to determine Broad-toothed Rat presence and relative abundance in relation to the level of feral horse impacts within the reserve. There was a significant negative relationship between feral horse impacts and both Broad-toothed Rat presence and abundance. No scats were identified at localities where feral horse impacts were severe, and at moderate horse impact sites, there was a proportion (34%) without scats found. Locations with low horse impacts had little impact on Broad-toothed Rat occurrence. As feral horse populations increase, Broad-toothed Rat populations may be further impacted. Such impacts will be due to the loss of vegetation cover from feral horse trampling and grazing, making animals more vulnerable to predation by predators or impacting on their ability to disperse to more suitable habitat. Habitat remnants and vegetation corridors along drainage lines require protection from feral horses to prevent localized extinctions of Broad-toothed Rat.