Ravens Can Figure Out When Someone Is Spying on Them

Jana Mueller
Jana Mueller

Corvids, the family of birds that includes crows and ravens, are canny beasts. They've been known to exercise self-control, count, hold grudges, and more. Now, new research suggests they possess at least a rudimentary Theory of Mind—the ability to attribute mental states to others.

A study in Nature finds that ravens can tell when someone else can see them, guarding their food when a peephole to their cache is open. While previous research suggested that birds might have an awareness of other animals' mental states, the results have been inconclusive. The Nature study is evidence that corvids can do more than just track other birds' gaze; they may understand the concept of "seeing."

Vienna-based researchers set up two rooms separated by windows that could be closed with covers. These covers had peepholes in them that could also be opened or closed. First, the 10 ravens were each allowed to cache food, while other birds were in the next room and the windows were open or closed. Then, they were trained to look through the peepholes to find food in the other room, so that they knew that the holes could be used to see through the window covers. Afterwards, each of the ravens was again presented with food with one of the two peepholes open. The adjacent observation room didn't have any birds in it, but the researchers played the sounds of another raven recorded during one of the previous trials.

When the birds heard the sounds of another raven in the next room, and the peephole was open, the birds behaved as if they knew they were being watched—they hid their cache of food quickly and didn't add more food to it as often, as if they knew that it might be compromised. However, they behaved normally when the peephole was closed.

This suggests that ravens don't just track their competitors' gaze to know when they’re being watched, but can infer from past experience when they can be seen.

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Amazon
Amazon

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Watch: In 1948, Idaho Officials Sent 76 Beavers Parachuting Into Idaho’s Wilderness

A young beaver with all four feet firmly on the ground.
A young beaver with all four feet firmly on the ground.
yrjö jyske, Flickr // CC BY 2.0

When people started building up the area around Idaho’s Payette Lake after World War II, its original residents began interfering with irrigation and agricultural endeavors. They weren’t exactly staging an organized protest—they were just beavers doing what beavers do.

Nevertheless, officials at the Idaho Department of Fish and Game decided their best bet was to find a new home for the long-toothed locals. The surrounding wilderness provided plenty of options, but transportation was another issue entirely. Traversing the undeveloped, mountainous terrain would require both trucks and pack animals, and experts knew from past relocation efforts that beavers weren’t fond of either.

“Beavers cannot stand the direct heat of the sun unless they are in water,” department employee Elmo W. Heter explained in a 1950 report [PDF]. “Sometimes they refuse to eat. Older individuals often become dangerously belligerent ... Horses and mules become spooky and quarrelsome when loaded with a struggling, malodorous pair of live beavers.”

To keep Payette Lake’s beavers healthy and happy during the journey, their human handlers would need to find another method of travel. As Boise State Public Radio reports, that’s when Heter suggested making use of their leftover WWII parachutes.

Two beavers would sit inside a wooden box attached to a parachute, which could be dropped from an airplane between 500 and 800 feet above their new home in the Chamberlain Basin. The cables that fastened the box to the parachute would keep it shut during the flight, but they’d slacken enough for the beavers to open the box upon landing. After testing the operation with weights, Heter and his colleagues enlisted an older beaver named Geronimo for a few live trials.

“Poor fellow!” Heter wrote. “You may be sure that ‘Geronimo’ had a priority reservation on the first ship into the hinterland, and that three young females went with him.”

Once Geronimo had certified the safety of the mission, the team began migrating the whole beaver population. During the fall of 1948, a total of 76 beavers touched down in their new territory. It wasn’t without tragedy, though; one beaver fell to his death after a cable broke on his box. Overall, however, the venture was deemed much safer (and less expensive) than any trip on foot would have been. And when department officials checked in on the beavers a year later, they had already started improving their ecosystem.

“Beavers had built dams, constructed houses, stored up food, and were well on their way to producing colonies,” Heter wrote. As Idaho Fish and Game’s Steve Liebenthal told Boise State Public Radio, the area is now part of “the largest protected roadless forest” in the continental U.S.

You can watch the Idaho Fish and Game Commission’s full 14-minute documentary about the process below.

[h/t Boise State Public Radio]