Feral Buffalo Effects on Critical Subsurface Refugia for Chelodina rugosa in Northern Australia

Abstract

Freshwater turtles worldwide face escalating threats resulting from habitat alteration, and the absence of detailed assessments for many taxa underscores the need for greater attention. In northern Australia, feral ungulates are a major driver of wetland degradation, with emerging evidence that buffalo activity threatens freshwater turtle populations. Modelling has identified the normally protective states of aestivation and embryo development in Chelodina rugosa as potential points of vulnerability amid escalating buffalo numbers. This study examined how buffalo alter subsurface conditions relevant to aestivation and nesting by quantifying rooted ground-layer vegetation, thermal regimes, gravimetric soil moisture and trampling in areas exposed to and excluded from buffalo over three habitat types in the Arafura Swamp Indigenous Protected Area. Buffalo presence markedly reduced subsurface habitat quality, increasing temperature and thermal variability, reducing soil moisture and rooted ground-cover vegetation and causing direct trampling of nests. These changes are likely to increase energetic costs during aestivation and reduce embryo survivorship. Such impacts on subsurface microhabitats are expected to intensify under predicted climatic changes and rainfall variability, further constraining the species' capacity to maintain successful aestivation over extended periods and maintain reproductive rates. Our findings highlight the need for targeted buffalo management to protect critical subsurface refugia for C. rugosa in northern Australian wetlands. Additionally, many other fauna rely on subsurface refugia during the dry season, including amphibians, other reptiles and invertebrates such as crustaceans and insects; these buffalo-induced impacts are likely to have much broader ecosystem-level consequences.