Red Foxes Visited All 26 Wolf-Killed Red Deer Carcasses and Responded More to Food Availability Than Wolf Activity
Red foxes (Vulpes vulpes) visited every one of 26 red deer (Cervus elaphus) carcasses killed by grey wolves (Canis lupus) and monitored in Stelvio National Park in the Italian Alps. Their presence was associated more strongly with the amount of edible carcass remaining than with whether wolves were present at or had recently visited the kill site.
The result captures a trade-off faced by smaller carnivores. Wolf kills provide a large, energy-rich food source that foxes do not have to hunt themselves, but returning wolves can also pose a risk. The researchers therefore tested whether foxes avoided carcasses at times when wolf activity made an encounter more likely.
Camera traps followed 26 wolf kills
The study covered the southern sector of Stelvio National Park from November 2022 to December 2024. Researchers located red deer carcasses confirmed as wolf kills and placed one camera trap 3–5 metres from each usable carcass. Cameras operated continuously for up to 25 days.
The amount of flesh remaining when each carcass was found was scored from almost completely consumed to essentially untouched. The researchers also recorded habitat and human activity and described wolf presence in several ways: whether wolves appeared in the same hour as a fox, whether they had appeared in the previous hour, how long it had been since the last wolf visit and how much time wolves spent at the carcass.
Foxes were recorded at all 26 carcasses. Wolves returned to 20 of them. Across the monitoring, the cameras produced 8,713 independent fox events compared with 414 wolf events, showing how intensively foxes exploited the food source after a kill.
Carcass profitability mattered more than wolf timing
The strongest predictor of fox occurrence was the initial state of the carcass — essentially how much food remained available. Foxes were also mostly nocturnal. Human activity and habitat features were also associated with fox presence to a lesser extent, while the measured wolf variables added little explanatory power.
The study found no detectable temporal avoidance or attraction at the hourly scale. Foxes were not consistently less likely to appear in the same hour as wolves, immediately after them or as a function of the time since a wolf visit. This does not prove that foxes perceive no risk from wolves. Rather, any fine-scale response was weak compared with the influence of food availability and normal daily activity rhythms.
Wolf kills became a resource for a smaller carnivore
Large ungulate carcasses contain far more food than a red fox could normally obtain from a single hunting event. By scavenging, foxes can gain energy without paying the cost of capturing the prey themselves. At the same time, the carcass is a place where they could encounter the much larger predator that created it.
In Stelvio, the food reward dominated the observed pattern. The universal fox use of the monitored red deer carcasses and the much higher number of fox than wolf events show that kills left by wolves became a repeatedly exploited resource. The study therefore illustrates one way an apex predator can affect smaller carnivores not only through competition or danger, but also by provisioning carrion that changes the local food landscape.
Ecology
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