Heading for greener pastures? Defining the foraging preferences of urban long-nosed bandicoots

The impact of urbanisation is delayed for many species, as populations that manage to survive the initial loss of habitat gradually decline throughout the urban–bushland mosaic. Yet many species’ chances of persistence within urban areas can be increased through relatively simple management techniques, and an understanding of how remnant populations use the interface between urban and natural landscapes is therefore crucial to their long-term management. Here we examine the habitat preferences of a semi-urban population of long-nosed bandicoots (Perameles nasuta) that inhabits a matrix of urban open lawn and dense native heath macrohabitats. We radio-tracked animals in these two distinct macrohabitats and compared the microhabitat features between core and peripheral areas of home ranges. Core and peripheral areas did not differ in their characteristics for either macrohabitat; however, individuals showed a high level of fidelity to distinct foraging patches. We then related microhabitat features to an index of foraging activity using generalised linear modelling and found that diggings were more abundant in areas with moist, soft soils close to cover. Soil softness and moisture were experimentally increased via artificial watering on selected sites. After only 10 days there were significantly more diggings on watered than non-watered sites. Thus, bandicoots appear to be a matrix-sensitive species, using some open grass areas of the matrix but requiring the vegetation cover of remnant bush. We suggest, however, that artificial watering and additional cover may be one way to increase foraging opportunities to make this, and other semi-urban, populations matrix-occupying, and thus facilitate bandicoot persistence in the urban mosaic.

Do kangaroos exhibit water-focused grazing patterns in arid New South Wales? A case study in Sturt National Park.

The density of kangaroos (Macropus spp.) within 5 km of current and former artificial watering points in Sturt National Park (NSW) was studied over a two-year period using the line transect method. Kangaroo densities were not significantly related to water proximity and did not significantly differ between open and closed watering points. Infrared sensors detected and counted kangaroo movements to and from artificial watering points and these were positively correlated with temperature. However, line transect counts did not reveal a shift in kangaroo distributions to water-proximate areas in warmer seasons. The results suggest that kangaroos travel to drink and then return to relatively stable home ranges that take advantage of sites offering the best grazing and resting opportunities. Vegetation surveys, using a wheel point device, revealed that the biomass of Atriplex spp. decreased significantly with increased proximity to artificial watering points, but the biomass of Poaceae spp. and numerous forbs did not. Vegetative diversity was unrelated to water proximity. Low vegetation biomass near artificial watering points in Sturt National Park may be more correctly attributed to the effects from past sheep-grazing pressure, than to any current grazing pressure. The implications of artificial watering point closure on conservation values and nature-based tourism are discussed.

The nature and modelling of piospheres: a review

Gradients in utilisation pressure tend to develop around watering points because water dependent herbivores are forced to congregate within a maximum distance of about 10-15 km from water in the dry season. Artificial watering points cause previously migratory or nomadic indigenous large herbivores to become sedentary, so that natural grazing patterns are disrupted. Under this altered grazing pattern, piosphere patterns tend to develop in herbaceous species composition, range condition, grass production, plant biomass, understory cover, standing crop and basal cover. In areas with large populations of elephants the density and canopy cover of trees is directly proportional to distance from watering points. In the absence of elephants an increase in woody plant density and canopy cover tends to occur in a zone just beyond a sacrifice area. Soil erosion, compaction and capping tend to occur at watering points on soils containing clay and silt. Artificial watering points are advantageous to the non-mobile water dependent large herbivore species and disadvantageous to the water independent large herbivore species. The processes underlying piosphere development and maintenance are numerous and diverse. While being parsimonious treatments of a complex system, conceptual models do provide a reasonable basis upon which to design an improved understanding. The logistic curve has been proposed as a convenient tool for estimating piosphere dimensions, but ignoring the 'best-fit' regression model for a piosphere data set may be an inaccurate practice. A large number of gradient models have been developed, each an attempt to shed some light on the behavioural response underlying what appears to be a complex grazing pattern. Several system models that take piosphere effects into account have been constructed. Some of these produce good simulations of herbaceous materi- al dynamics and especially good simulations of bush dynamics.