Spatial patterns of kangaroo density across the South Australian pastoral zone over 26 years: aggregation during drought and suggestions of long distance movement

Abstract

Summary 1.Wildlife surveys usually focus on estimating population size, and management actions such as commercial harvesting, culling and poison baiting are referenced commonly to population size alone, without taking into account the way in which those animals are distributed. This paper outlines how point-based aerial survey data can be converted to continuous density surfaces using spatial analysis techniques. Using this approach, we describe and explore the spatial patterns of density of two species of kangaroos in an area exceeding 200 000 km 2 in South Australia over a 26-year period. 2. Densities of red and western grey kangaroos were estimated in 2 km 2 segments along aerial survey transect lines, yielding point density estimates. Universal kriging provided an unbiased interpolation of these data using the spatial autocorrelation structure described by the semi-variogram. The Getis statistic identified clusters of high and low kangaroo density. 3. Considerable year-to-year variation in the spatial patterns of kangaroo density was observed. In many cases, annual rates of increase over large areas were too high to be explained by vital rates alone, implying immigration from surrounding areas. These large shifts in distribution were occasionally to areas that had received better rainfall than the surrounding areas. For both species, there was no obvious local spatial autocorrelation pattern or clustering of kangaroo density beyond that described by average density and the present set of management regions, suggesting the latter are appropriate divisions for harvest management. 4. Data for both species fitted the power law relationship extremely well. During dry times, red kangaroos, but not western grey kangaroos, were more aggregated, supporting past ground observations at a fine spatial scale. 5. Synthesis and applications . Kriged density surfaces enable estimation of kangaroo density on individual properties, which are the management units at which harvest quotas or culling approvals are allocated. These estimates will be marked improvements over systematic sampling estimates when sampling intensity is low. Predictions of shifts in kangaroo distribution using rainfall or satellite imagery will allow more accurate allocation of harvest quotas. Similarly, predictions of more even kangaroo dispersion following high rainfall will allow managers to anticipate downturns in harvest rate.

Searching for sustainability: are assessments of wildlife harvests behind the times?

“…This result could also be due to animal dispersal/immigration that is not being properly captured by demographic harvest models (Pople et al . ).…”

“…), kangaroo monitoring in Australia (Pople et al . ) and global fisheries and aquaculture monitoring by the Food and Agriculture Organization of the United Nations (FAO ).…”

Are the faecal pellets of kangaroos(Macropusspp.) a source of nutrients and carbon in an inland floodplain wetland during flooding? A preliminary experimental inundation study in the Macquarie Marshes, New South Wales

“…We further hypothesize that the distribution and productivity of food sources and water availability for kangaroos across the floodplain are important in determining the nutrient and carbon supplies from kangaroo faecal pellets. This is because environmental conditions affect densities of kangaroo populations, as well as their home range movements and feeding habitats (Caughley et al 1985;Johnson et al 1987;Dawson et al 2004;Pople et al 2007). Faecal pellets of kangaroos a source of nutrients and carbon Terrestrial and aquatic systems alternate in floodplain wetlands.…”

“…The faecal pellets of kangaroos contain nutrients such as nitrogen and phosphorus, and carbon in the form of carbohydrates (Hume 1974;Wann and Bell 1997) that derive from their food such as grasses, flowering plants, forbs, leaves, tree bark and shrubs (Taylor 1983;Short 1986;Meers and Adams 2003;Murphy and Bowman 2007). Kangaroos can travel large distances (Priddel et al 1988;Jaremovic and Croft 1987;Pople et al 2007) and use different habitats (Johnson et al 1987;Priddel 1988;Murphy and Bowman 2007). They may play a significant role in nutrient and carbon cycling in inland floodplain wetlands of Australia.…”

Spatial resource allocation modeling for marine protected areas design: The case of Kaomei coastal wetland

“…Of the most commonly used methods, natural resource studies often use the Kriging method (Oliver and Webster, 1990). Numerous ecological studies have used rasterbased maps of the biomass or the Shannon diversity index generated by the Kriging model to indicate the spatial distributions of species or functional groups (Kienel and Kumke, 2002;Dunton and Schonberg, 2003;Bretagnolle et al, 2004;Hernandez-Stefanoni and Ponce-Hernandez, 2006;Monestiez et al, 2006;Pople et al, 2007;Wang, 2007).…”