Interspecific and geographic variation in the diets of sympatric carnivores: dingoes/wild dogs and red foxes in south-eastern Australia

Abstract

Dingoes/wild dogs (Canis dingo/familiaris) and red foxes (Vulpes vulpes) are widespread carnivores in southern Australia and are controlled to reduce predation on domestic livestock and native fauna. We used the occurrence of food items in 5875 dingo/wild dog scats and 11,569 fox scats to evaluate interspecific and geographic differences in the diets of these species within nine regions of Victoria, south-eastern Australia. The nine regions encompass a wide variety of ecosystems. Diet overlap between dingoes/wild dogs and foxes varied among regions, from low to near complete overlap. The diet of foxes was broader than dingoes/wild dogs in all but three regions, with the former usually containing more insects, reptiles and plant material. By contrast, dingoes/wild dogs more regularly consumed larger mammals, supporting the hypothesis that niche partitioning occurs on the basis of mammalian prey size. The key mammalian food items for dingoes/wild dogs across all regions were black wallaby (Wallabia bicolor), brushtail possum species (Trichosurus spp.), common wombat (Vombatus ursinus), sambar deer (Rusa unicolor), cattle (Bos taurus) and European rabbit (Oryctolagus cuniculus). The key mammalian food items for foxes across all regions were European rabbit, sheep (Ovis aries) and house mouse (Mus musculus). Foxes consumed 6.1 times the number of individuals of threatened Critical Weight Range native mammal species than did dingoes/wild dogs. The occurrence of intraguild predation was asymmetrical; dingoes/wild dogs consumed greater biomass of the smaller fox. The substantial geographic variation in diet indicates that dingoes/wild dogs and foxes alter their diet in accordance with changing food availability. We provide checklists of taxa recorded in the diets of dingoes/wild dogs and foxes as a resource for managers and researchers wishing to understand the potential impacts of policy and management decisions on dingoes/wild dogs, foxes and the food resources they interact with.

Fig 1. The State of Victoria, south-eastern Australia.

The nine Victorian regions defined by the Australian Government Bureau of Meteorology are: 1, Mallee; 2, Wimmera; 3, Northern Country; 4, North East; 5, East Gippsland; 6, West and South Gippsland; 7, Central; 8, North Central; and 9, South West.

Fig 2. Photographs demonstrating ecosystem variation within the State of Victoria: (a) semi-arid Mallee ecosystem (Photo: Mallee Fire and Biodiversity Project Team); (b) farmland (Photo: Jim Radford); (c) Box Ironbark forest (Photo: Andrew Bennett); (d) wet forest (Photo: Wiki commons).

Fig 3. Percentage frequency occurrence of seven diet categories recorded in (a) wild dog scat, and (b) fox scat samples collected during 1983–2014 in nine Victorian regions and all regions pooled: Mallee; Wimmera; Northern Country; North East; East Gippsland; West and South Gippsland; Central; North Central; and South West.

Sample sizes are provided in Table 1.

Fig 4. Regional variation in intake of key mammalian food items (≥0.04 kg prey biomass per scat) by wild dogs based on analysis of scats collected during 1983–2014 in (a) all Victorian regions, and in the (b) Mallee, (c) Wimmera, (d) Northern Country, (e) North East, (f) East Gippsland, (g) West and South Gippsland, (h) Central, (i) North Central, and (j) South West regions.

Sample sizes are provided in Table 1.

Fig 5. Regional variation in intake of key mammalian food items (≥0.04 kg prey biomass per scat) by foxes based on analysis of scats collected during 1983–2014 in (a) all Victorian regions and in the (b) Mallee, (c) Wimmera, (d) Northern Country, (e) North East, (f) East Gippsland, (g) West and South Gippsland, (h) Central, (i) North Central and (j) South West regions.

Sample sizes are provided in Table 1.

Fig 6. Mass (kg per scat) of eutherian predator species in the diets of wild dogs (n = 5148) and foxes (n = 11,143) in Victorian regions, based on analysis of scats collected during 1983–2014.

Fig 7. Number of individuals (per scat) of threatened native Critical Weight Range (35–5500 g) mammal species in the diets of wild dogs (n = 5148) and foxes (n = 11,143) in Victoria, based on analysis of scats collected during 1983–2014.