Past research suggests that social organisation in Australian rodent species is determined by the predictability of resources in the environment (Happold 1976a). Notomys alexis (the spinifex hopping mouse or tarrkawarra) is widely distributed throughout the Australian arid-zone (Breed 1998a; Watts & Aslin 1981). Large groups of animals have been found sharing burrows in the wild and laboratory observations suggest that the species is highly social (Happold 1976a; Stanley 1971). A closely related species, Notomys mitchelli (Mitchell’s hopping mouse or pankot) is relatively common throughout the southern semi-arid zone (Watts 1998a; Watts & Aslin 1981). Much less is known about N. mitchelli; field studies have been subject to low recapture rates and few laboratory studies have involved this species (Baverstock 1979; Cockburn 1981a; Crichton 1974). Following Happold (1976a), it was hypothesised that the socio-ecology of N. mitchelli will be qualitatively different to that of N. alexis. Studying wild populations of Notomys mitchelli in the Middleback Ranges, South Australia and N. alexis outside the desert township of Roxby Downs, S.A., this research aimed to describe the socio-ecology of these species, with reference to the predictability of their environments. Uniquely, bioclimatic modelling of the species’ known distributions was also conducted to confirm that the study’s underlying assumption that the two rodents inhabit essentially different environments was correct. These studies were complemented by the observation of captive groups of N. alexis. This work confirmed that the habitats of Notomys mitchelli and N. alexis are distinct; the more arid habitat of N. alexis is subject to greater environmental fluctuations than that of the semi-arid dwelling N. mitchelli. Contrary to expectations, however, observation of free-living animals characterised N. mitchelli social groups as highly unstable; while particular individuals remained in the population for long periods, many animals appeared to be transients. Further, burrow groups appeared to be much smaller than predicted by Happold (1976a), and based on loose aggregations of male animals rather than small groups of females. While decidedly social in the laboratory, free-living N. alexis lived in groups no bigger than N. mitchelli and these groups were equally ephemeral in constitution. Moreover, free-living N. alexis appeared to utilise activity areas that were no larger than those used by N. mitchelli, despite occupying a more unpredictable and apparently less well-resourced habitat. As a whole, this research represents a comprehensive examination of the principal behavioural theory commonly applied to Australian native rodent species, untested since its publication three decades ago. From the data collected during this work, it cannot be said that the environmental predictability hypothesis for native rodent social organisations as proposed by Happold (1976a) is adequate to differentiate the social behaviour of these semi-arid and arid-dwelling species. Instead, it is suggested that, while both N. mitchelli and N. alexis are undoubtedly socially tolerant, predation and/or parasite load, driving burrowing behaviour, has a greater influence on the social behaviour of free-living rodent populations than habitat predictability. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1373743 / Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2009

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

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