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In
humans, the eyes are said to be the "window to the soul," conveying much about
a person’s emotions and intentions. New research demonstrates for the first
time that birds also respond to a human’s gaze.
Predators
tend to look at their prey when they attack, so direct eye-gaze can predict
imminent danger. Julia Carter, a graduate student at the University of Bristol,
and her colleagues, set up experiments that showed starlings
will keep away from their food dish if a human is looking at it. However, if
the person is just as close, but their eyes are turned away, the birds
resumed feeding earlier and consumed more food overall.
"This
is a great example of how animals can pick up on very subtle signals and use
them to their own advantage," Carter said. Her results are published
online in the April 30, 2008 edition of the journal Proceedings of the Royal Society B.
Wild
starlings are highly social and will quickly join others at a productive
foraging patch. This leads to foraging situations that are highly competitive.
An individual starling that assesses a relatively low predation risk, and
responds by returning more quickly to a foraging patch (as in the study), will
gain valuable feeding time before others join the patch.
Responses
to obvious indicators of risk — a predator
looming overhead or the fleeing of other animals — are well documented, but
Carter said that a predator’s head orientation and eye-gaze direction are more
subtle indicators of risk, and useful since many predators orient their head
and eyes towards their prey as they attack.
This
research describes the first explicit demonstration of a bird
responding to a live predator’s eye-gaze direction.
"By
responding to these subtle eye-gaze cues, starlings would gain a competitive
advantage over individuals that are not so observant," Carter said. "This
work highlights the importance of considering even very subtle signals that
might be used in an animal’s decision-making process."
Do these
birds understand that a human is looking at them, and that they might pose some
risk?
As yet, this question has not been answered.
But whether or not the responses involve some sort of theory
of mind, and whether or not they are innate or acquired, the result is that
starlings are able to discriminate the very subtle eye-gaze cues of a nearby
live predator and adjust their anti-predator responses in a beneficial manner.
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