Red foxes feasting on Australian wildlife

By Trish Fleming. The fox is one of the world’s most widespread carnivores. A key to its success has been its broad, opportunistic diet. They eat anything, from insects to mammals, live prey to carrion. They are known predators of turtle eggs, digging up nests of eggs and newly hatched young. They love poultry and will also take other livestock – basically anything they can carry off. Foxes even rummage through human refuse, with stomach contents sometimes revealing items still in their plastic wrapping.

Foxes are one of the greatest threats to Australia’s native fauna. Since its introduction to Australia about 150 years ago, the red fox (Vulpes vulpes) has contributed to the extinction of an estimated 14 native mammal species and one bird species (Woinarski et al., 2019), and to the ongoing suppression or decline of many others (Stobo-Wilson et al., 2021).

Over the last 70 years, many authors have studied the diet of Australian foxes, summing up the toll on native wildlife. We reviewed 85 fox diet studies (totalling 31693 samples) to identify patterns in food taken by foxes over this time (Fleming et al., 2021).

We found that mammals were present in 70% of all samples, making up a major component of fox diet. Native species such as possums and bandicoots were a significant proportion of the foxes’ diet especially in urban bushland reserves. In farmland, livestock and house mice were often consumed.

For study sites within mouse plague-prone parts of eastern Australia there was no difference in the incidence of house mouse in fox diet between years with mouse plagues (23% of samples) and years without plagues (also 23% of samples). However, the incidence of house mouse in fox diet for these areas was ~2.3 times greater than the overall mean in other locations (10%), suggesting that foxes benefit from localised increases in mouse availability, even if their exploitation of localised abundances is insufficient to counter the rapid reproductive rate of mouse populations under ‘ideal’ plague conditions (usually drought years followed by a good year).

Invertebrates (38% of samples) and plant material (26% of samples) were also both staple foods, and often the dominant food category recorded. Foxes often had stomachs full of grapes, figs, olives, or even cherries (for the most discerning South Australian foxes).

Birds (13% of samples) and reptiles (10% of samples) were also commonly reported. Both groups can be identified from stomach contents or scats from only a few feathers or scales. By contrast, we found that frogs were scarcely represented in fox diet studies (averaging only 1.6% of samples) and were generally only recorded for studies that examined stomach contents.

Biogeographical differences reveal factors that likely determine prey availability. Diet composition varied with ecosystem, level of vegetation clearing and condition, as well as climate zone. Fox diet also varied seasonally, reflecting activity patterns of prey species and food availability.

As a precautionary principle, population control of foxes, feral cats, and rabbits should be carried out simultaneously, because removal of any one of these species in isolation can have perverse repercussions for native wildlife. Integrated pest species management is therefore needed to meet biodiversity conservation outcomes. 

We found a major shift in fox diet over the past 70 years, as they have switched to consuming more native species in the wake of successful rabbit biocontrol.

Mammal groups that showed a change in incidence in the diet of the red fox (Vulpes vulpes) with year of study (*p<0.05, ** p<0.01, *** p<0.001). Left hand column shows scatterplots of frequency of occurrence (FOO) over year of collection (x axis); the vertical red lines represent two introductions of Rabbit Haemorrhagic Disease Virus (1: RHDV and 2: RHDV-1 K5) into Australia. Middle column shows boxplots grouping data for three time periods (rabbit control 0= pre-RHDV, 1=post-RHDV-1, 2=post-RHDV-2), reflected in a decrease in lagomorph FOO (principally European rabbit Oryctolagus cuniculus) in the diet of foxes (b). Right hand column shows inverse relationships in incidence of lagomorphs with native mammals, macropods and native rodents.

References

Fleming, P. A., H. M. Crawford, A. M. Stobo-Wilson, S. J. Dawson, C. R. Dickman, S. J. Dundas, M. Gentle, T. M. Newsome, J. O. Connor, R. Palmer, J. Riley, E. G. Ritchie, J. Speed, G. Saunders, J.-M. D. Stuart, E. Thompson, J. M. Turpin, and J. C. Z. Woinarski. 2021. Diet of the introduced red fox Vulpes vulpes in Australia: analysis of temporal and spatial patterns. Mammal Rev. In press

Stobo-Wilson, A. M., B. P. Murphy, S. M. Legge, D. G. Chapple, H. M. Crawford, S. J. Dawson, C. R. Dickman, T. S. Doherty, P. A. Fleming, M. Gentle, T. M. Newsome, R. Palmer, M. Rees, E. Ritchie, J. Speed, J.-M. Stuart, E. Thompson, J. Turpin, and J. C. Z. Woinarski. 2021. Reptiles as food: predation of Australian reptiles by introduced red foxes compounds and complements predation by cats. Wildl. Res. In press

Woinarski, J. C. Z., M. F. Braby, A. A. Burbidge, D. Coates, S. T. Garnett, R. J. Fensham, S. M. Legge, N. L. McKenzie, J. L. Silcock, and B. P. Murphy. 2019. Reading the black book: the number, timing, distribution and causes of listed extinctions in Australia. Biol. Cons. 239:108261.

https://phys.org/news/2021-05-red-foxes-feasting-australian-mammals.html

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