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Buffel Grass Cenchrus ciliaris is a major environmental threat to biodiversity in central Australia and is rapidly expanding its distribution on National Parks and other areas of conservation concern. Managers need appropriate mapping of the potential and current Buffel Grass distribution at a broad landscape scale in order to prioritize their use of limited resources for survey and control efforts. Watarrka National Park was used as a case study to trial the effectiveness of aerial survey for mapping Buffel Grass distribution. Over 7 000 aerial observations were recorded from transects across the whole Park. Ground truthing indicated an acceptable level of accuracy for the aerial derived data at 84%, and a Kappa coefficient of 49. The aerial survey data were used to build a surface probability model for the entire Park based on environmental variables using Generalized Linear Modelling and then applied using a Geographic Information System. Distance to drainage and distance to tracks, followed by ruggedness, hummock grass cover and soil texture were the most important explanatory variables in determining the probability of occurrence of Buffel Grass. The surface model was overlaid with available vegetation mapping to quantify the level of threat to native plant diversity, in particular rare plant species diversity. This information is useful in developing a strategy for managing Buffel Grass at a landscape scale that is based on invasive potential and known biodiversity values, where previous management has focused on small scale site specific control actions.

Radio-telemetry was used to examine the home range, movement and habitat utilisation of the critically endangered Carpentarian rock-rat (Zyzomys palatalis) in an isolated habitat patch in the Gulf of Carpentaria hinterland over a 13-month period. Two home-range estimators were used in the study, (i) minimum convex polygon (MCP) and (ii) fixed Kernel (KL), the latter also being used to estimate core areas of activity. Based on a total sample size of 21 individuals, the mean MCP home range was 11 165 m2, similar to the mean KL home range of 10 687 m2. Core areas were, on average, 11.9% of the KL home-range estimate. There was no significant difference in the size of home range or core area of males and females. Juveniles had a significantly smaller home range than adults. Home ranges and, to a lesser degree, core areas were non-exclusive, with multiple areas of overlap (averaging 41% and 38% respectively) within and between all age and gender categories, but especially between males and between juveniles. Movement frequencies showed that animals made many short forays in a central area close to the arithmetic home-range mean and far fewer long forays of distances greater than 100 m from the central area. The spatial and temporal activity of Z. palatalis was concentrated in, but not confined to, the 'valley' and 'slope' habitats, with fewer movements of rats onto the surrounding 'plateau'. Resource selection analyses showed that Z. palatalis tended to prefer valley and slope habitats over the plateau and that the proportion of point locations was significantly higher for adults in the slope habitat and for juveniles in the valley habitat. Most home ranges were centred on the ecotone between these two habitat types. Although isolated and spatially limited, these habitat patches provide high-quality resources for dense populations of Z. palatalis. This study exemplifies a species' attempt to make efficient use of a limited resource in an otherwise hostile environment. Even small declines in habitat area or quality due to their vulnerability to fire would impact upon many animals.

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