for National Geographic News
For the crow-like birds known as jackdaws, it's all in the eyes.
The species may be the only animal aside from humans known to understand the role of eyes in seeing and perceiving things, according to a new study.
While humans often use visual clues to communicate, it wasn't known whether other animals share this social ability.
Jackdaw eyes, like those of humans, are unusually conspicuous, with dark pupils surrounded by silvery white irises.
The physical similarities hint that jackdaws use their eyes to communicate in the same ways humans do, said study leader Auguste von Bayern, a zoologist currently with the University of Oxford.
"We can communicate a lot via the eyes, and jackdaws do that as well, in my opinion," von Bayern said.
Now her study of hand-reared jackdaws shows that the birds—members of the same family as crows and ravens—can use a human's gaze to tell what that person is looking at.
"They are sensitive to human eyes because they are sensitive to their own species' eyes," von Bayern said.
By contrast, previous studies have shown that other animals regarded as intelligent, such as chimpanzees and dogs, find even their own species' eyes hard to read.
Conflict and Cooperation
Von Bayern conducted the jackdaw experiments while completing her Ph.D. at the University of Cambridge.
In one test, she and colleague Nathan Emery timed how long a jackdaw took to retrieve food if a person was also eyeing the prize.
They found that the birds took longer to retrieve the food if the human was unfamiliar—someone the bird apparently didn't trust.
The birds were equally sensitive to the gaze of a single eye, such as when the person looked at the food in profile or kept one eye closed.
This suggests the jackdaws made the decision to risk conflict solely based on eye motion and not on other cues, such as the direction a potential rival's head was facing.
In a second experiment, the birds were able to interpret a familiar human's altered eye gaze to "cooperate" to find food that was hidden from view.
The study authors add that more tests will be needed to tell if the birds were able to read eye movements based on their natural tendencies or if it is a learned behavior from being raised by humans.
Findings appear this month in the online issue of the journal Current Biology.
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