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

Pople, Anthony R., Phinn, Stuart R., Menke, Norbert, Grigg, Gordon C., Possingham, Hugh P. and McAlpine, Clive M. (2007) Spatial patterns of kangaroo density across the South Australian pastoral zone over 26 years: Aggregation during drought and suggestions of long distance movement. Journal of Applied Ecology, 44 5: 1068-1079. doi:10.1111/j.1365-2664.2007.01344.x


Author Pople, Anthony R.
Phinn, Stuart R.
Menke, Norbert
Grigg, Gordon C.
Possingham, Hugh P.
McAlpine, Clive M.
Title Spatial patterns of kangaroo density across the South Australian pastoral zone over 26 years: Aggregation during drought and suggestions of long distance movement
Journal name Journal of Applied Ecology   Check publisher's open access policy
ISSN 0021-8901; 1365-2654; 1365-2664
Publication date 2007-10
Sub-type Article (original research)
DOI 10.1111/j.1365-2664.2007.01344.x
Volume 44
Issue 5
Start page 1068
End page 1079
Total pages 12
Editor R. Freckleton
G. Kerby
Place of publication Oxford, England
Publisher Blackwell Publishing
Collection year 2008
Language eng
Subject 270708 Conservation and Biodiversity
270500 Zoology
C1
779902 Land and water management
050104 Landscape Ecology
Abstract 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 km2 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.
Keyword Ecology
Australia
geostatistics
interpolation
kangaroos
distribution
Western Grey Kangaroos
Sympatric Red Kangaroos
Macropus-rufus
Population-dynamics
Aerial Survey
Wales
Fuliginosus
Models
Environments
Dependence
Q-Index Code C1
Q-Index Status Confirmed Code
Additional Notes Citation: ANTHONY R. POPLE, STUART R. PHINN, NORBERT MENKE, GORDON C. GRIGG, HUGH P. POSSINGHAM, CLIVE McALPINE (2007) Spatial patterns of kangaroo density across the South Australian pastoral zone over 26 years: aggregation during drought and suggestions of long distance movement, Journal of Applied Ecology 44 (5), 1068–1079. doi:10.1111/j.1365-2664.2007.01344.x -- Published Online: 30 Jun 2007

 
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Created: Mon, 17 Sep 2007, 16:06:05 EST by Ms Sarah Boulter on behalf of School of Biological Sciences