Planet Earth

Powerful Ravens Sabotage Others' Relationships

InkfishBy Elizabeth PrestonNov 7, 2014 2:01 PM

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If we're lucky, this is behavior we haven't seen since high school. The coolest individuals can't stand to see others gaining social status, so they cut down any peers who are starting to elevate themselves. Ravens have to live with this behavior all the time. When the top-dog birds see others building new relationships, they attack these birds or put themselves in the middle. They may as well be spreading rumors or defacing each other's lockers. Wild ravens living in Austria were the ones to reveal this behavior to scientists. The ravens, a group of about 300 birds in the Austrian Alps, have discovered that a local zoo is a convenient source of food. So the wild birds hang around the captive animals year-round (they especially like the wild boar enclosure) and steal their provisions. Because of this, they're used to seeing humans nearby. For years, scientists have been capturing these birds, marking them with colored leg bands, and studying their social behavior. Now University of Vienna cognitive biologist Jorg Massen and his coauthors asked whether the most dominant birds might be sabotaging those lower down in the group. The raven social ladder goes like this: at the top are breeding, male-female pairs—the power couples. Just below them are couples that don't have their own breeding territory yet. Below them are birds that are still trying to solidify a relationship with a mate; these are called "loosely bonded" pairs. Single ravens are at the bottom of the ladder. For six months, researchers spied on this raven population. They monitored the flirtatious, bond-forming interactions between ravens: sitting shoulder to shoulder, touching each other's beaks, grooming one another's feathers, playing. They saw that 19 percent of these interactions were interrupted by another bird. The intruder would either attack the couple or just plop itself in between them. This kind of interruption halted the canoodling a little more than half the time. But in another quarter of cases, the couple fought back at the intruder and chased it off. "[We] were wondering why they would do such a thing," Massen says. "What's in it for them?" In other words, why did these third-wheel ravens care enough about what the others were doing to risk their own safety breaking it up? To find out, the researchers looked at the social status of both the couples being interrupted and the birds interrupting them. They found that loosely bonded individuals—those ravens still trying to build a relationship with a mate—were interrupted most often. And the birds jumping in between them usually belonged to a strongly bonded couple. It seemed that the most dominant birds were trying to keep new couples from forming

. Massen thinks this is powerful ravens' strategy for staying on top. By preventing new pairs from forming, they reduce their competition. They can keep more territory for themselves and more food for their own babies. Single birds apparently aren't worth their attention, and other strongly bonded couples might be too difficult to break up. But by focusing on the pairs that are just starting out, the powerful ravens target their effort where it serves them best. The researchers haven't yet seen how these machinations benefit the dominant ravens (if they do). Massen says he's now gathering data to find out whether the interruptions truly prevent other birds from forming pairs. The bullies seem to think it's worth it, anyway. For ravens at the bottom of the social ladder, it means finding a partner is going to be even more life-changing than finally getting those braces off. Update (12:18 PM): This post has been edited to add comments from Jorg Massen.Image: by Ingrid Taylar

(via Flickr)

Massen, J., Szipl, G., Spreafico, M., & Bugnyar, T. (2014). Ravens Intervene in Others’ Bonding Attempts Current Biology DOI: 10.1016/j.cub.2014.09.073

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