Scientists thought ravens followed wolves. They were wrong

A new study tracking ravens and wolves in Yellowstone National Park over two-and-a-half years reveals a much more advanced strategy. Instead of trailing wolves, ravens remember locations where kills are likely to happen and return to those areas, even from great distances. "They can fly six hours non-stop, straight to a kill site," says Dr. Matthias Loretto, the study's first author.

Published in Science, the research shows that ravens rely on spatial memory and navigation to locate food spread across the landscape. "Ravens can cover large distances by flying, and they seem to have a good memory, so they don't need to constantly follow wolves in order to profit from the predators," says Loretto.

The project was led by the Research Institute of Wildlife Ecology at the University of Veterinary Medicine Vienna and the Max Planck Institute of Animal Behavior (Germany), along with several international partners, including the Senckenberg Biodiversity and Climate Research Centre (Germany); School of Environmental and Forest Sciences at the University of Washington (USA); and Yellowstone National Park (USA).

Tracking Ravens and Wolves in Yellowstone

The research took place in Yellowstone National Park, where wolves were reintroduced in the mid-90s after a 70-year absence. Today, about a quarter of the wolf population carries tracking collars each year. Dr. Dan Stahler, a Yellowstone biologist who has studied these wolves since their return, notes that ravens often appear closely tied to them: "You see them flying directly above traveling packs or hopping close behind wolves as they take down prey."

This behavior made sense, since wolves create reliable feeding opportunities for scavengers. "We all assumed that the birds had a very simple rule; just stick close to the wolves," says Stahler. But that idea had never been directly tested. "We didn't know what ravens were capable of because nobody had ever put them at the center; nobody had taken the scavenger's point of view," he says.

To better understand raven behavior, researchers fitted 69 birds with small GPS trackers, an unusually large number for this type of study. "Ravens are so observant of the landscape that they don't step into traps easily," says Loretto. To successfully capture them, the team carefully blended traps into the surroundings. For instance, traps near campsites were disguised with trash and fast food. "Or else the ravens would suspect that something was off and wouldn't come near it," says Loretto, now at the University of Veterinary Medicine Vienna.

In addition to the raven data, the team analyzed movement patterns from 20 collared wolves. They focused on winter, when ravens most often interact with wolves, recording raven locations every 30 minutes and wolf locations every hour. They also documented where and when wolves killed prey, mainly elk, bison, and deer.

Ravens Remember Productive Hunting Areas

Over the course of two-and-a-half years, researchers found only one clear example of a raven following a wolf for more than one kilometer or more than an hour. "At first, we were puzzled," says Loretto. "Once we realized that ravens are not following wolves over long distances, we couldn't explain why the birds still arrive so quickly at wolf kills."

A closer look at the data revealed the answer. Instead of shadowing wolves, ravens repeatedly returned to specific areas where kills were more common. Some birds traveled up to 155 kilometers in a single day, flying in direct paths toward places where a carcass was likely to appear, even though the exact timing of a kill cannot be predicted.

Wolf kills tend to cluster in certain parts of the landscape, such as flat valley bottoms where hunting is more successful. Ravens visited these high-yield areas far more often than places where kills were rare. This pattern suggests they learn and remember what researchers call a long-term "resource landscape."

"We already knew that ravens can remember stable food sources, like landfills," says Loretto. "What surprised us is that they also seem to learn in which areas wolf kills are more common. A single kill is unpredictable, but over time some parts of the landscape are more productive than others -- and ravens appear to use that pattern to their advantage."

What This Reveals About Animal Intelligence

The researchers say ravens may still follow wolves over short distances when they are nearby. "To find wolf kills locally, ravens likely use short-range cues, like monitoring wolf behavior or listening to wolf howling," says Loretto. But on a larger scale, memory plays the leading role. Ravens decide where to search first based on past experience, sometimes traveling tens or even hundreds of kilometers.

Senior author Prof John M. Marzluff of the University of Washington explains: "What our study clearly shows is that ravens are flexible in where they decide to feed. They don't stay tied to a particular wolf pack. With their sharp senses and memory of past feeding locations, they can choose among many foraging opportunities far and wide. This changes how we think about how scavengers find food -- and suggests we may have underestimated some species for a long time."