Crows — like dolphins, elephants chimpanzees and us. — use tools. In particular, New Caledonian crows (Corvus moneduloides) on France’s South Pacific territory craft complex tools out of sticks, leaves or other materials and insert these into deadwood or vegetation to pull out insects or other prey.
The New Caledonian crows’ intelligence extends to their being able to reason that an agent, even if it cannot be seen, is responsible for an action. That is, when these crows see something amiss in their environment (the leaves of a tree shaking in an unusual way suggesting it might not just be the wind, but perhaps an animal such as a monkey) they think there must be something behind it and change their actions accordingly.
As Ars Technica explains, researchers created a scenario in which eight New Caledonian crows were placed in a room with a box containing food and a stick. The scientists also set up a blind behind which they could hide and, via a hole, could tap the crows on the head lightly with a stick. The researchers “expressly avoided doing so,” Ars Technica underscores:
First, two researchers entered the room—one went behind the blind and one stayed in plain sight. The one behind the blind would push the stick through the hole a number of times, and then both the humans would leave the room. In the second version, one researcher would enter the room and stand in plain sight while the stick was manipulated from outside the room (via pulleys) and then leave the room. In each case, the behavior of the crow was monitored after the humans left. They watched to see how many times the crow eyeballed the hole to make sure a stick wasn’t coming out while it used the food box.
The idea was this: if the crows were capable of thinking of the stick as being manipulated by a hidden human, they wouldn’t worry about the stick once the human behind the blind left. When the stick did its thing, but no human walked out, on the other hand, they’d be very suspicious that the stick would start moving again at any moment.
Indeed, when the crows saw the stick move but no human passing by, they were noticeably agitated. They investigated the hole and approached the box with the food but then retreated from it without retrieving anything. That is, they did not consider the food box to be safe if, after the stick moved, they did not see a human actually leaving.
You can watch the crows showing off their smarts here:
Ars Technica quotes the researchers that “it is, therefore, possible that the ability to reason about hidden causal agents is far more widespread in the animal kingdom than has been thought previously.”
Another study offers some evidence of how New Caledonian crows’ morphology enables them to use tools. Using an ophthalmoscope video camera, researchers under Jolyon Troscianko of the University of Birmingham in central England, have discovered that the position of these crows’ eyes and their unusually straight bills plays a part in their tool-using ability.
As reported in the journal Nature Communications, the scientists discovered that, because these crows’ eyes are more forward-positioned instead of sideways-positioned, they have “substantially greater binocular overlap” than other species of crows who have similar cognitive abilities. Their “unusually straight bill” also “enables a stable grip on tools, and raises the tool tip into their visual field’s binocular sector.”
Might these crows have evolved specific morphological features to enable them to hunt for food, to better use their intelligence?
In other words, take it as a compliment if someone says you have a bird brain.
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Photo by Danny Chapman