Converting rangelands to reserves: Small mammal and reptile responses 24 years after domestic livestock grazing removal

Does reducing grazing pressure or predation conserve kowaris? A case study at Diamantina National Park

Livestock contributes to the decline of many species in Australia. However, they may have less impact in arid environments, where annual plant species dominate. Kowaris (Dasyuroides byrnei), a small carnivorous marsupial, living on Diamantina National Park were monitored to assess the success of ecosystem recovery following a reduction in cattle. Kowaris were found at 10 locations within the study area: five where they had been recorded prior to the area becoming a national park and five ‘new’ locations. No kowaris were found at one of the historical sites. The density was estimated to range from 1 to 2.5 kowaris per square kilometre from 2007 to 2009. The results suggest that the population likely increased following a reduction in grazing pressure. However, a boom in rodents and predators occurred during the study with a corresponding decline in kowari detections. Kowaris have not been detected at any of the study sites since 2012. These results suggest that management of top-down factors as well as bottom-up factors are required to conserve kowaris. The work further highlights the need for replicated, long-term studies if the interactions between complex ecological processes, at a landscape scale, are to be understood so that threatened species, like the kowari, can be managed effectively.

Potential drivers of common brushtail possum (

Australia’s terrestrial mammalian fauna have experienced severe declines since European settlement. On the Murray–Darling floodplain in south-eastern Australia, common brushtail possums (Trichosurus vulpecula, ‘possums’), have contracted to riparian zones. Although an important possum refuge, little is known about possum population dynamics here. We examined possum population dynamics and potential drivers across two decades on the Murray River floodplain at Calperum Station. We related possum density to satellite derived fractional cover, (a measure of the proportion of green, non-green and bare ground cover), and contextualised these findings using tree condition and grazing pressure datasets. Possum surveys were conducted between 1998 and 2019 in riparian and non-riparian habitats and density was modelled in relation to fractional cover values of green, non-green, and bare ground. Possum density fluctuated between 1998 and 2008 but in 2018 and 2019, possums were undetectable. Possum density was negatively associated with bare ground and positively associated with non-green. Overgrazing by kangaroos likely reduced vegetation cover and diversity and contributed to possum decline, via a reduction in possum food resources and increased exposure to predation. Inconsistent monitoring meant that the population decline was not detected until after it had occurred, and management interventions were not triggered, highlighting the dilemma of allocating scarce monitoring resources.