An Indonesian species of parrot known as the Goffin’s cockatoo (Cacatua goffiniana) can tear a cardboard sheet into long strips as tools to reach food, but fails to adjust strip width to fit through narrow openings, according to a new study published online this week in the journal PLoS ONE.
Captive Goffin’s cockatoos are capable of inventing and manipulating tools, even though they aren’t known to use tools habitually.
“The Goffin’s cockatoo is neither a specialized tool user nor a habitual tool user on a population wide level such as New Caledonian crows,” explained study lead author Dr. Alice Auersperg of the Medical University of Vienna and colleagues.
“They are also neither nest builders nor food cachers, which are believed to be important preconditions for the development of avian tool use.”
“Nevertheless, they combine and modify environmental objects during exploration and play, which can cause individual tool innovations in captive and potentially also in feral individuals.”
In the study, Dr. Auersperg and co-authors aimed to address two main questions: can Goffin’s cockatoos adjust the properties of their tools to save effort, and, if so, how accurately do they attend to the properties of their tools relative to their respective function during tool manufacture?
The researchers supplied six adult cockatoos with large cardboard sheets to tear into strips as tools for the testing apparatus: a food platform with a food reward set at varying distances (1.6-2.4 inches, or 4-16 cm) behind a small opening which also varied in width (0.4-0.8 inches, or 1-2 cm).
They found that the birds were capable of adjusting the length of their cardboard strip tools to account for variations in food distance, making shorter tools when the reward was closer than when it was set farther away.
In every case, if a first-attempt tool was too short, the second-attempt tool would be significantly longer.
On average, all six birds made significantly longer tools than were required to reach the reward in all test conditions, with the birds tending to make increasingly long tools as the study progressed — perhaps as a risk-avoidance strategy.
However, only one bird was able to make a sufficiently-narrow tool to successfully reach the food reward when the opening was at its narrowest.
“The shearing technique the birds use to tear the cardboard limits the narrowness of the resulting strips,” the study authors said.
“In future studies, we will provide less restrictive materials to assess whether Goffin’s cockatoos are cognitively capable of adjusting tool width in this situation.”
“The way they inserted and discarded manufactured pieces of specific lengths differently depending on condition suggests that the cockatoos could indeed adjust their tool making behavior in the predicted direction but with some limits in accuracy,” Dr. Auersperg said.
A.M.I. Auersperg et al. 2018. Tool making cockatoos adjust the lengths but not the widths of their tools to function. PLoS ONE 13 (11): e0205429; doi: 10.1371/journal.pone.0205429