Ravens appear to share negative emotions with one another, but not positive ones.

by Carolyn Wilke

Here’s a downer: Pessimism seems contagious among ravens. But positivity? Not so much.

When ravens saw fellow birds’ responses to a disliked food, but not the food itself, their interest in their own food options waned, researchers report May 20 in the Proceedings of the National Academy of Sciences. The study suggests that the birds pick up on and even share negative emotions, the researchers say.

Ravens are “very good problem solvers … but this paper’s really highlighting their social intelligence as well,” says Andrew Gallup, a psychologist at SUNY Polytechnic Institute in Utica, N.Y., who was not involved in the study. The work paints a richer picture of how the birds’ brains work, he says.

Known for their smarts, ravens act in ways that suggest a capacity for empathy, such as by appearing to console a distressed comrade. Thomas Bugnyar, a cognitive ethologist at the University of Vienna, and his colleagues wanted to look into one building block of empathy — whether animals share emotions. To be able to feel for others, an animal needs to be able to feel like others, he says.

But sizing up an animal’s mood is tricky. Scientists generally rely on behavioral or physiological cues to clue into a creature’s emotional state. More challenging is assessing how one animal’s mood might influence another’s: Similar actions appearing to stem from kindred emotions may just be mimicry.

To tune into the moods of ravens, the researchers set up experiments to watch whether the birds reacted positively or negatively to a neutral stimulus. This so-called cognitive bias test, used on a wide variety of animals from bees to pigs, “is basically … asking how you would judge a glass — if it’s half full or half empty,” Bugnyar says.

Eight ravens, tested in pairs, were first given a choice between a box containing a cheese treat and an empty box. Once the birds learned the location of each option, they were given a third box in a new spot that hadn’t been used in the training. Whether a bird acted as if the box was a trick or a treat indicated a cognitive bias, interpreted as pessimism or optimism.

Next, one bird in a pair was offered both unappealing raw carrots and tastier dried dog food before one was taken away. Birds left with the treat moved their heads and bodies as they studied it, while those getting the carrots appeared crankier, spending less time attending to the offering and sometimes kicking or scratching elsewhere. The other bird in the pair watched these reactions from a separate compartment, without being able to see the researcher or which food the bird received.

Both birds then performed the cognitive bias test again. This time, observer birds that had seen their partner appearing perky showed on average the same level of interest in their own ambiguous box as they had previously. But those that had seen their partner reacting negatively typically took more than twice as long to approach the ambiguous box. This dip in the observer birds’ interest was somehow influenced by seeing their partner’s apparent disappointment, the researchers say.

Each bird was tested four times, half of the time with the undesired food and the other half with the treat.

It’s interesting that while the negative responses seemed contagious, the positive ones did not, Gallup says. This may be because negative reactions are easier to provoke or observe, or because animals tune in more to negative information in their environment, the authors say.

The ravens study marks one of the first times the cognitive bias test has been used to examine emotions and social behavior, says coauthor Jessie Adriaense, a comparative psychologist at the University of Vienna. “Emotions are extremely important drivers of our behavior, but how they actually drive animals … is still an open question,” she says. To truly understand what motivates behavior in animals, scientists need to delve deeper into their emotions, she says.

Bad moods could be contagious among ravens

Wild crows seem to obey ‘do not enter’ signs

Crows can’t read, but the signs have still apparently curbed their habit of stealing insulation material from a university building in Japan.

by Russell McLendon

Crows are incredibly clever birds. Some species use tools, for example. Some also recognize human faces, even “gossiping” about who’s a threat and who’s cool. Crows can hold long-term grudges against people they deem dangerous, or shower their allies with gifts. Oh, and they can solve puzzles on par with a 7-year-old human.

With wits like this, it’s little wonder crows have adapted to live in human cities around the world. Yet despite all their uncanny displays of intelligence, a recent example from Japan is eyebrow-raising even for these famously brainy birds.

Wild crows had learned to raid a research building in Iwate Prefecture, stealing insulation to use as nest material. But as the Asahi Shimbun reports, they abruptly quit after a professor began hanging paper signs that read “crows do not enter.”

The idea was suggested by a crow expert from Utsunomiya University, and has reportedly worked for the past two years. This doesn’t mean the crows can read Japanese, but it may still shed light on their complex relationship with people.

The building in question is the International Coastal Research Center (ICRC), part of the University of Tokyo’s Atmosphere and Ocean Research Institute in Otsuchi. The ICRC was founded in 1973 to promote marine research around the biodiverse Sanriku Coast, but its building was heavily damaged by the 2011 Great East Japan earthquake and tsunami, which flooded all three stories. Nearby houses were all destroyed, the Asahi Shimbun reports, and many residents have moved elsewhere.

Repairs later allowed temporary use of the third floor, but the first and second floors were just cleared for warehouse space. While the University of Tokyo has plans to rebuild the center and restart its research, that “is expected to cost a substantial amount of money and several years of time,” according to the ICRC website.

The crows began their raids on the damaged building in spring 2015, according to Katsufumi Sato, a behavioral ecologist and ethology professor at the University of Tokyo. Once inside, they would find insulated pipes, tear off chunks of insulation and then fly away, leaving behind feathers and droppings as clues of their crime.

“Crows take it for their nests,” Sato tells Shimbun staff writer Yusuke Hoshino.

Hoping for a simple solution, ICRC staff sought advice from Sato, who in turn asked his friend Tsutomu Takeda, an environmental scientist and crow expert at Utsunomiya University’s Center for Weed and Wildlife Management. When Takeda suggested making signs that tell crows to stay out, Sato says he thought it was a joke. But he gave it a try, and crows quit raiding the ICRC “in no time at all,” Hoshino writes.

Sato remained skeptical, assuming this was a temporary coincidence, but the crows stayed away throughout 2015, even though the building still had openings and still had insulation inside. He put up the paper signs again in 2016, and after another year without crow attacks, he kept up the tradition this spring. Crows can still be seen flying around nearby, Hoshino points out, but their raids seem to have ended.

So what’s going on? Crows can’t read, but could they still somehow be getting information from the signs? As the BBC documented a decade ago, some urban crows in Japan have learned to capitalize on traffic lights, dropping hard-to-crack nuts into traffic so cars will run over them, then waiting for the light to turn red so they can safely swoop down and grab their prize. That’s impressive, albeit not quite the same.

Takeda offers a different explanation. The crows aren’t responding to the signs at all, he says; they’re responding to people’s responses. People might normally ignore common urban wildlife like crows, but these warnings — while ostensibly directed at crows themselves — draw human attention to the birds. As ICRC staff, students and visitors see the strange signs, they often look up at the crows and even point at them.

“People gaze up at the sky [looking for crows], you know,” Takeda says.

For clever birds that pay close attention to people, that’s apparently eerie enough to make the ICRC seem unsafe. It’s worth noting this is anecdotal, not a scientific study, and there may be another reason why the crows stopped their raids. But given how closely it correlated with the new signs, and how perceptive crows can be, Takeda’s plan is being credited with cheaply and harmlessly keeping the birds at bay.

If nothing else, this is a reminder to appreciate these intelligent birds living all around us, even in cities we built for ourselves. But since crows are sometimes a little too good at exploiting urban environments, it’s also a helpful reminder of how much a dirty look can accomplish. Sato, now a believer in Takeda’s unorthodox strategy, hopes more people will come to the ICRC and gawk at the local crows.