Ravens anticipate wolf kill sites across broad scales.

Scavengers generally rely on patchily distributed, unpredictable carrion. A long-standing hypothesis suggests scavenging ravens reliably locate such food by directly following large carnivores to their kills. However, by satellite tracking 69 ravens, 20 wolves, and 11 cougars in Yellowstone National Park, we found that following of predators over large distances rarely occurred. Instead, ravens routinely revisited sites where wolf kills were common—returning from distances of up to 155 kilometers to find carrion. Much like navigating to permanent anthropogenic subsidies, ravens appear to remember potential sources of carrion shaped by previous encounters with wolves or their kills. These findings suggest that spatial memory and navigation play a considerably greater role than previously assumed among scavengers, and possibly other wide-ranging species, in search of ephemeral resources. Editor's summary: Many species make their living by scavenging from kills made by other species. Observational knowledge posits that they do this by following predators around. Lorretto et al. tested this assumption by tagging ravens, wolves, and cougars in Yellowstone National Park. They found that the ravens weren't following the predators; instead, they regularly returned to sites where they had encountered wolf kills before, like bats returning to known fruiting trees at the right time. These results suggest that scavengers may also use spatial memory of ephemeral resources in their search for food. —Sacha Vignieri [ABSTRACT FROM AUTHOR]