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Cockatoos can recognize the need for a tool set

Until now, chimpanzees have stood out as the only non-human animals to make use of a tool set. This means they can use two or more different tools, with separate functions, to achieve a single goal. Not only this, but they also recognize the need to bring all components of the tool set along in order to succeed. 

The most famous example of this is given by the chimpanzees of the N’doki forest in northern Congo, when they fish for termites. They need both a short, rigid stick for opening the termite nest, and a long, thin probe to reach deep into the nest and access the termites. Some of the chimpanzees carry around both of these tools when foraging for termites, instead of starting with the short stick and then heading off to look for a thin probe once the nest is open.

Recent experimental research has now shown that Goffin’s cockatoos (Cacatua goffiniana) can also make use of a tool set. These small, white birds from the parrot family are indigenous to parts of Indonesia and have been shown to be competent tool users, and even capable of making their own tools to help extract seeds from a fruit. 

Up until now, though, it wasn’t clear whether the cockatoos considered these tools as a “set.” It’s possible that what may look like a tool set is instead nothing more than a sequence of single tool uses, with the need for each new tool occurring to the animal as the task evolves.

In a new study, published in the journal Current Biology, researchers have used controlled experiments to clarify that the cockatoos do indeed recognize when a job requires more than one tool. “With this experiment we can say that, like chimpanzees, Goffin’s cockatoos not only appear to be to using tool sets, but they know that they are using tool sets,” said study first author Antonio Osuna-Mascaró, an evolutionary biologist at the University of Veterinary Medicine Vienna. “Their flexibility of behavior is stunning.”

The experiments were set up to mimic the termite fishing behavior of the famous chimpanzees. Each of ten cockatoos was faced with a perspex box containing a cashew nut. In order to access the nut, the bird had to insert a short, rigid stick through a grid in the box and puncture a membrane. Then the bird had to switch tools to a long, flexible straw that was cut in half longways, and poke this through the hole it has just made in the membrane. By waving the straw around, the bird could dislodge the nut. 

Of the ten cockatoos, seven were able to use the tool set successfully and reach the criterion of nine successful trials. The two star birds, Figaro and Fini, solved the problem on their very first attempt, taking only 31 and 34 seconds respectively. The cockatoos don’t have an equivalent foraging behavior in the wild, so their tool use could not have been based on any innate behaviors, and each cockatoo used a slightly different technique when trying to access the nut. 

Next, the team tested the cockatoos’ ability to change their tool use in a flexible manner depending on the situation. To do this, they presented each cockatoo with two different types of box: one with a membrane in front of the nut, and one without. The cockatoos were given the same two tools, but they only needed the pointy stick when a membrane was in the way. “The cockatoos had to act according to the problem; sometimes the tool set was needed, and sometimes only one tool was enough,” said Osuna-Mascaró.

All of the cockatoos mastered the test in a very short period of time and were able to recognize when a single tool was sufficient. However, the birds engaged in an interesting behavior during this choosing phase. “When making the choice between which tool to use first, they were picking one up, releasing it, then picking up the other one, releasing it, returning to the first one, and so on,” said Osuna-Mascaró. The researchers found that when cockatoos did this switching, they performed better on the tests.

Next, the team tested the cockatoos’ ability to transport the tools as a set on an as-needed basis. They put the cockatoos through a series of increasingly challenging trials to reach the boxes: first they had to climb a short ladder while carrying their tools; then they had to fly horizontally with them; and in the final test, they had to carry the tools while flying vertically. As before, the birds were only sometimes presented with a box with a membrane barrier, so they had to decide whether the problem required one or both tools.

Some cockatoos learned to carry the two tools together – by inserting the short punching stick into the groove of the halved straw – when they were presented with a box that required both. This meant they only had to make one trip, albeit while carrying a heavier tool set. Most of the cockatoos transported the toolset on an as-needed basis, further indicating that they could judge beforehand whether two tools were required, though some made two trips when necessary. One cockatoo, Figaro, decided not to waste time thinking and instead carried both tools in almost every trial.

“We really did not know whether the cockatoos would transport two objects together,” said study senior author Alice Auersperg, a cognitive biologist at the University of Veterinary Medicine Vienna. “It was a little bit of a gamble because I have seen birds combining objects playfully, but they very rarely transport more than one object together in their normal behavior.”

There’s a lot more to be learned about cockatoo tool use, the researchers say. “We feel that, in terms of technical cognition and tool use, parrots have been underestimated and understudied,” said Auersperg.

“We’ve learned how dexterous the cockatoos are when using a tool set, and we have a lot of things to follow-up on,” noted Osuna-Mascaró. “The switching behavior is very interesting to us, and we are definitely going to use it to explore their decision making and their metacognition – their ability to recognize their own knowledge.”

By Alison Bosman, Staff Writer

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