Clever craftsmen: tool using cockatoos save effort by making tools of different lengths

Goffin-Cockatoos are able to manufacture longer or smaller sticks out of cardboard in relation to the distance of food in a puzzlebox. (Photo: ©Bene Croy)

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The Goffin Cockatoo is one of very few animal species able to manufacture tools but even so it is a major intellectual challenge to produce a tool that is suited to a specific situation. A new study by researchers from Vetmeduni Vienna and the University of Vienna now confirms that the clever Cockatoos can flexibly adjust the length of their tools as required by cutting longer or shorter sticks out of cardboard. They even reject tools immediately that they deem unsuitable. The birds’ abilities reach their limits if they have to adjust their tools to the width of the test openings. The limitation seems to be due to how wide they can open their beak, which they use like a hole puncher to produce tools.

Only very few animal species such as the great apes and a few birds can use or even make their own tools to fish for out-of-reach food. Nevertheless, making different tools depending on the situation at hand represents a considerable cognitive challenge even for habitually tool making animals.

Researchers from the University of Veterinary Medicine in Vienna and the University of Vienna studied tool manufacture in an Indonesian cockatoo, in which the capacity for using tools was recently discovered. A previous study showed that the animals were able to spontaneously innovate the manufacture of long fishing or probing tools, biting them out of sheets of different material, including cardboard. As cardboard is not pre-structured it required the animals to actively shape their tools. They made them by placing a large number of parallel bite-marks alongside the edge of the material like a hole puncher and used their curved upper beak to cut the elongated piece out of the cardboard block after reaching a certain length.

In the present study which was published in the scientific journal Plos ONE, the scientists were able to show that the cockatoos pay attention to specific functional features of their tools while making them: “They made significantly longer cardboard stripes when a food reward was further away and shorter stripes when the food was closer to a probing hole in a puzzle box” explains Carina Köck, a student who conducted the study at the Goffin Lab. “ If they do make tools that are not long enough to breach the distance between the food reward and the probing hole they usually discard them before even trying to insert them into the box and immediately make a longer one” she adds. “They even discard notably longer tools when the food is far away than when it is close.”

“The way the animals show flexibility in their tool making behaviour between different distances, suggest that they at least learn to pay attention to different conditions” says Alice Auersperg the head of the Goffin Lab. “As longer cardboard stripes required more parallel bitemarks we have an continuous increase in investment in the manufacture of longer tools and it is likely that the animals were able to save effort” she elaborates. “Nevertheless, as time passed they did eventually fall into a strategy of making long tools most of the time. It is likely that they either became more efficient in their tool manufacture thereby reducing the aforementioned investment or as a strategy of avoiding the risk of having to discard a tool of insufficient size.”

Nevertheless, the flexibility of the animals had its limits when it came to adjusting the diameter of their cardboard stripes. Even when the diameter of the probing hole varied, the animals kept making stripes of similar width. The shape of their beaks is likely to restrictive in this respect as the animals used a specific technique for making them: “The lower edge of the upper beak takes a steep curve from the beak tip to the corner of their mouth. The edge of the cardboard block is pressed into the deepest possible point of that curve during tool making. This is most likely done for for support.” says Köck.  “Meanwhile the beak tip was used to cut through the material. This means that the distance between the beak tip and the curve restricted the width of their tools.”

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