Ravens don’t follow wolves to dinner – they remember where the food is

(Press-News.org) New findings challenge the long-held idea that scavengers seeking food routinely follow predators to find it. Studying common raven, gray wolf, and cougar in Yellowstone National Park, researchers found that ravens rarely trail predators over long distances; instead, they rely on spatial memory to return to places where kills have occurred before. Scavenger species that rely on the kills of predators face the challenge of finding food that is patchily distributed, unpredictable, and often ephemeral because many animals compete for it. A widely accepted hypothesis suggests that scavengers solve this problem by adjusting their movements to follow large carnivores to their kills. Although scavengers are frequently observed near carnivores in the field, it’s unclear whether following behavior reflects the dominant foraging strategy. However, this hypothesis has been difficult to evaluate due to the challenge of simultaneously tracking predators and scavengers across large distances.

 

Matthias-Claudio Loretto and colleagues investigated how common raven locate carrion by studying their interactions with grey wolf and cougar in Yellowstone National Park. Ravens are often seen traveling with wolves and rapidly gathering at fresh kills. Loretto and colleagues hypothesized ravens may rely on memory and prediction to revisit areas where predators frequently make kills, rather than following them in real time. Loretto et al. used GPS devices to track the movements of ravens, wolves, and cougars over 2.5 years, as well as records of hundreds of wolf and cougar kills. Contrary to longstanding assumptions, the authors found that long-distance predator following was rare. Instead, ravens repeatedly returned, sometimes from distances of up to 155 kilometers, to areas where wolf kills were common. Raven-cougar interactions were rare. The findings indicate that ravens rely on spatial memory, treating areas with historically high kill density as predictable foraging sites. According to the authors, this suggests that navigation and memory, rather than real-time tracking of predators, play the dominant role in how ravens locate food sources.

 

Podcast: A segment of Science's weekly podcast with Matthias-Claudio Loretto, related to this research, will be available on the Science.org podcast landing page after the embargo lifts. Reporters are free to make use of the segments for broadcast purposes and/or quote from them – with appropriate attribution (i.e., cite "Science podcast"). Please note that the file itself should not be posted to any other Web site.

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