Australian Journal of Zoology Australian Journal of Zoology Society
Evolutionary, molecular and comparative zoology

Evolution of sexual segregation in mammalian herbivores: kangaroos as marsupial models

G. Coulson A C , A. M. MacFarlane A , S. E. Parsons A B and J. Cutter A
+ Author Affiliations
- Author Affiliations

A Department of Zoology, The University of Melbourne, Vic. 3010, Australia.

B Current address: Lower Murray–Darling Catchment Management Authority, Buronga, NSW 2739, Australia.

C Corresponding author. Email:

Australian Journal of Zoology 54(3) 217-224
Submitted: 24 September 2005  Accepted: 24 April 2006   Published: 22 June 2006


Sexual segregation is best known in sexually dimorphic ungulates. Many hypotheses have been proposed to explain the evolution of sexual segregation in ungulates, but all are reducible to the influence of two factors: body size and sex-specific reproductive strategy. Definitive tests of these hypotheses are lacking in ungulates because these factors are confounded, all males being somewhat larger than females. Kangaroos represent a parallel radiation of terrestrial herbivores, but their populations are composed of a spectrum of adult body sizes, ranging from small males the same size as females to large males more than twice the size. We exploited this heteromorphism to assess the independent influences of size and sex in these ungulate analogues. We conducted a preliminary study of western grey kangaroos (Macropus fuliginosus) in north-western Victoria, Australia. Adult males predominately occupied grassland habitat, whereas females occurred mostly in lakebed, woodland and shrubland. Single-sex groups occurred more often than expected during the non-mating season. The diet of large males had the highest proportion of grass, and females had the least. These initial results indicate that both size and sex influence segregation in this species, confirming the worth of kangaroos as marsupial models for research into the evolution of sexual segregation.


Parks Victoria staff at Hattah-Kulkyne National Park were generous with their time, particularly Phil Murdoch, as well as David Bone, David Christian and Danielle McLennan. Bill Barker shot the kangaroos with professionalism and patience, and Turi Berg helped with habitat surveys. Scott Laidlaw and Steve Mueck assisted with vegetation identification and analysis. Fred de Munk and David Paul advised us on slide preparation and imaging. Helena Bender, Kirstin Long, Grainne Maguire, Genevieve Morris, Marissa Parrott and Alexa Ryhorchuk offered sound advice and scrutinised drafts. We also thank Ruth, Phil, Nick and Marc for their support. All work in the park was carried out under Department of Natural Resources and Environment research permit 10001674 in accordance with the Code of Practice for the Humane Shooting of Kangaroos, endorsed by the Council of Nature Conservation Ministers (ANPWS 1995). This project was funded by a grant (S1991097) from the Australian Research Council to Graeme Coulson, and an Australian Postgraduate Award to Abigail MacFarlane.


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