1. Ravens can plan ahead.
Ravens know how to save up for a rainy day. Or, at least the very next day.
A duo of researchers in Sweden set up a series of tasks for ravens involving tools and bartering to see how well ravens could plan for the future, outside of their normal food caching behavior. The first task involved training the ravens to drop a box down a tube to open a box to receive a treat. Then, the birds were shown a tray that included a rock and "distracter objects" — metal pipes, balls, wheels and a toy car — to see if they would pick the rock and use it to claim a treat later. Given a 15-minute delay between selecting the object and being given access to the treat box, ravens were successful 86 percent of the time. When there was a delay of 17 hours, their success rate actually went up to 88 percent.
Another task involved trading a token for a treat. Here, ravens were trained to barter a specific token to receive a treat from a human. Sometimes the treat-trading human would not have a treat as a way to incentive planning. Once that was achieved, a different human would offer them a tray that had the token and more distracter objects. The birds had to select and save the correct object for later use. And they did so. In fact, the ravens would delay their gratification, ignoring an immediately available treat, once they learned that they could trade the token for a larger treat. The scientists did learn that would only wait for a few seconds for a larger reward. If the reward was too far in the future, it had less value.
Previously, this sort of planning behavior was thought to be limited to humans and great apes (the ravens were actually better planners than than orangutans, bonobos and chimpanzees when compared to the apes' results in similar bartering experiments). As to how the birds evolved to develop this sort of complex cognition, the jury's still out. Can Kabadayi, one of the researchers who conducted the study, told NPR that neurons, environmental pressures and previous interactions with other ravens could play a role in the skills. And speaking of other ravens ...
2. Ravens can keep track of the social status of other ravens both in their own group and in groups of unfamiliar ravens.
This is a useful strategy particularly if a raven has any plans to leave its group and join another — the bird will know just where it fits in the pecking order and also who to be submissive to.
Researchers discovered this by experimenting with playing conversations between ravens to a subject raven, conversations that reversed the social ranking that the subject raven was familiar with.
IFLScience writes, "They found that ravens paid especial attention and seemed stressed — displaying behaviors like head turns and body shakes — when they hear playbacks that simulate a rank reversal in their group. They just didn’t expect a low-ranking bird to show off to a higher-ranking one — this violates their rank relations. They were fine when the dominance structure in the playback reflects their hierarchy accurately. The ravens also responded to simulated rank reversals in neighboring groups, suggesting that they’ve figured out who’s boss among unknown birds just by watching and listening to them (since there was no physical contact between groups). It’s the first evidence of animals tracking rank relations of individuals that don’t belong to their own group — a useful skill for a bird switching foraging units."
So, ravens learn social ranks well enough to even figure out what's what in foreign groups of ravens with whom they've never actually interacted. In other words, ravens are savvy politicians.
3. Ravens can remember individual human faces.
Researchers have experimented with wearing masks while trapping and tagging crows. They wore a particular mask when trapping and releasing crows, and then had another neutral mask that wasn't used when trapping. They discovered that crows learned and recognized the "face" of the trapper. And not only that — they teach their offspring and other group members just who is who so that their friends and family could avoid being trapped by the masked person.
The New York Times writes, "In the months that followed [the trapping and tagging], the researchers and volunteers donned the masks on campus, this time walking prescribed routes and not bothering crows. The crows had not forgotten. They scolded people in the dangerous mask significantly more than they did before they were trapped, even when the mask was disguised with a hat or worn upside down. The neutral mask provoked little reaction. The effect has not only persisted, but also multiplied over the past two years. Wearing the dangerous mask on one recent walk through campus, Dr. [John] Marzluff said, he was scolded by 47 of the 53 crows he encountered, many more than had experienced or witnessed the initial trapping. The researchers hypothesize that crows learn to recognize threatening humans from both parents and others in their flock."
4. Ravens can solve puzzles.
Ravens have incredible problem-solving skills. In some experiments, they are presented with a new puzzle, which they study for a bit and then speedily solve.
Science Blogs writes about one set of experiments by researchers Bernd Heinrich and Thomas Bugnyar, "They found that some adult birds would examine the situation for several minutes and then perform this multistep procedure in as little as 30 seconds without any trial and error — as if they knew exactly what they were doing. Because there was no opportunity for the birds to be confronted with a similar problem in the wild, the simplest explanation is that they were able to imagine the possibilities and to perform the appropriate behaviors. The authors also found that successfully performing this behavior required maturity: immature birds were unable to do it while year-old birds performed a variety of trials before they were able to succeed."
So not only can they figure out puzzles surprisingly quickly, but they learn from past experience to build on their conclusions about how to get what they want. In this PBS video, a raven figures out how to pull up a fishing line to steal the catch.
This is just the tip of the iceberg when it comes to how ravens have displayed their intelligence and strategizing abilities. If you'd like to learn more, check out the book "In the Company of Crows and Ravens." By the time you finish the last page, you'll never look at ravens in the same way again.
Related on MNN: How smart are you about crows and ravens?