"No other animalnot even a chimphas ever spontaneously solved a problem like this, a fact that puts crows in a class with us as toolmakers," Savage writes in her book.
Kacelnik noted that New Caledonian crows, which are restricted to a few islands in the South Pacific Ocean, are the only example of some 45 crow species that "are very intense tool users in nature."'
(See a map of the South Pacific.)
Nevertheless, he continued, these birds are "both intense tool users and creative tool users In addition to the tools they are normally seen to use in the wild, they are capable of making new instruments when the necessity arises," such as the wire hooks.
In research published last year in the journal Nature, Kacelnik and his colleagues demonstrated that New Caledonians are born toolmakersthat there is a genetic component to the behavior.
The finding, Kacelnik said, fits the notion that higher intelligence requires a genetic imprint to foster more advanced behaviors like learning and innovation.
"There are three elements: what animals inherit, what animals learn by individual experience, and what animals acquire through social input," he said.
"It's a mistake to believe [these elements] compete. Actually, they coalesce, they enhance each other."
The intelligence of other crow species, most notably ravens, is also demonstrated by their ability to manipulate the outcomes of their social interactions, according to book author Savage.
For example, she highlights raven research by University of Vermont zoologist Bernd Heinrich showing how juvenile and adult ravens differ when feeding on a carcass.
The juveniles cause a ruckus when feeding to recruit other young ravens to the scene for added safety against competition with adult crows and other scavengers.
The adults, by contrast, show up at a carcass in pairs and keep quiet to avoid drawing attentionand competitionto the food.
Savage also discusses Swiss zoologist Thomas Bugnyar's research showing how a raven named Hugin learned to deceive a more dominant raven named Mugin into looking for cheese morsels in empty containers while Hugin snuck away to raid full containers.
"This shady behavior satisfies the definition of 'tactical', or intentional, deception and admits the raven to an exclusive club of sociable liars that in the past has included only humans and our close primate relatives," Savage writes in her book.
Another area of crow research that may indicate higher intelligence is how crows learn and use sound. Preliminary findings suggest that family groups develop their own sort of personal dialects, according to Savage.
"There's a lot more going on in a bird brain than people ten years ago would have imagined," she said.
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