LOS ANGELES — Humans and other primates aren’t the only members of the animal kingdom who can watch total strangers interact and figure out who’s in charge. Ravens can do it too, according to a new study in the journal Nature Communications.
Researchers at the University of Vienna said they had several reasons to suspect that ravens had the chops to understand the social hierarchy of unknown birds just by looking at them. For starters, ravens “are renowned for their relatively big brains,” they wrote.
Among other things, these noggins allow them to switch between foraging in groups and looking out for themselves. Their big brains also seem to help them keep track of social relationships that have nothing to do with reproduction (usually an animal’s top priority). Some ravens have even been known to console their buddies after losing a fight.
So the researchers selected 16 captive members of the Corvus corax species and rotated them through an aviary to give them a chance to see and hear other birds, though they remained physically separated. Then the researchers played audio of other birds from hidden loudspeakers.
Some of these “vocal interactions” reflected the actual social hierarchy of the group. Other audio clips had the dominance and submissive calls scrambled, to mimic a reversal in rank.
When the male ravens heard the clips that didn’t match their expectations, they seemed to withdraw (perhaps to give themselves a chance to figure out what was going on). The birds “reduced their vocalizations” and “tended to reduce their behaviors indicative of showing attention,” the researchers found. The female ravens, in contrast, didn’t seem too concerned about the scrambled recordings.
The story was different when the researchers played audio clips of ravens in the test subjects’ own social groups. In these cases, clips that didn’t match the birds’ expectations caused them to stress them out, especially the female birds, the researchers found. This may be because female ravens try to boost their own rank by bonding with males, according to the study. But the clips that reinforced their (accurate) ideas about the social hierarchy of their feathered friends were taken in stride.
“This is, to our knowledge, the first experimental demonstration that non-human animals may recognize the rank relations of out-group members,” the researchers wrote.