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A comparison of the red fox (Vulpes vulpes) and feral cat (Felis catus) diets in the south west region of Western Australia

Crawford, Heather (2010) A comparison of the red fox (Vulpes vulpes) and feral cat (Felis catus) diets in the south west region of Western Australia. Honours thesis, Murdoch University.

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There is a paucity of data on the diet of red foxes (Vulpes vulpes) and feral cats (Felis catus) in the south west region of Western Australia. Information is needed to determine the impact of these introduced predators on native wildlife, and to establish whether competitive and predatory interactions are likely to exist between foxes and cats. Therefore the diets of both species were quantified and compared by examining the stomach contents of 542 foxes and 56 cats collected from across the south west region in association with the Red Card for the Red Fox community feral control program. This study provides the first insight into the summer dietary preferences of the red fox and feral cat in south west Western Australia.

This study provided a ‘snapshot’ of dietary intake, revealing that there was little overlap in the diets of red foxes and feral cats (26%), with the proportions of different prey categories consumed differing significantly between the predators (ANOSIM- R=0.1352, p<0.0001). Overall, foxes consumed mostly domestic sheep as carrion or lamb (64%, using Index of Relative Importance values for this food category), as well as a large amount of fruit, grains and invertebrates. With numerous bird species as their staple prey (32%, by IRI), feral cats are actively hunting a greater proportion of native vertebrate species (43%, by IRI), than foxes (6%, by IRI). Surprisingly, cats deliberately consumed a large amount of plant material (18%, by IRI), which may suggest that this atypical food source plays a role in sustaining feral cats during summer.

From analysis of fox and cat diets it can be surmised that in the south west, interspecific competition between the predators may not be strong because of their reliance on different food categories. However, removal experiments and investigation of spatial interactions between the two species are required to confirm that resource partitioning and not antagonistic interactions are causing dietary differences (e.g. interference competition).

Findings from the current study into the diets of red foxes and feral cats have implications for both farmers and conservationists in the south west. If carrion is responsible for sustaining large fox populations (hyperpredation) during a period of reduced resources, removal of carrion may reduce fox population sizes substantially. If, however, active control of foxes then leads to mesopredator release, feral cats may have a greater impact on the south west’s remaining native species, especially if cats have increased access to carrion.

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Biological Sciences and Biotechnology
Supervisor: Fleming, Trish, Calver, Michael and Adams, Peter
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