Monkeys do it, man of course, but also a few bird species - they use tools to achieve certain goals. In recent years, especially the New Caledonian Crows (Corvus moneduloides) baffled biologists with their amazing abilities: The clever ravens of the tropical Pacific island of New Caledonia cleverly produce sophisticated tools to fish for insects in tree holes and understand complex relationships. The question then came up: Why did it seem that only the New Caledonian Crow has produced these technological abilities among the numerous species of the corvidae family? Especially the species of remote tropical islands are very little explored, emphasize the researchers around Christian Rutz of the University of St Andrews. "There could still be some undiscovered tool users, " says the biologist.
The impetus for the current study was an anatomical peculiarity of the known tool users: New Caledonia crows have strikingly straight beaks - which has earned them the German name Geradschnabelkrähe. "We wondered if this could be a typical adaptation to holding tools, similar to the thumb's thumb, " says Rutz. By searching for this feature in other raven birds, the researchers finally came across a promising candidate: The Hawaiian crow (Corvus hawaiiensis) also has a comparatively straight beak.
It is a species that has barely escaped a tragic end: it was heavily persecuted on its home island of Hawaii, especially at the end of the 20th century, and finally eradicated in the wild - only a few animals survived in captivity. Today there are around 100 of these unique ravens. These same animals - the entire living population of the Hawaiian crow - eventually became the experimental animals of the researchers. The staff at the San Diego Zoo offspring program were delighted to be contacted by the scientists and gladly participated in the study on the targeted use of their Hawaiian crow tools. "We had already seen the use of the Stocher tool, but did not pay any attention to the observations, " says Bryce Masuda of the Hawaii Endangered Bird Conservation Program.
Now, experiments and video footage clearly document the highly developed skills of the Hawaiian crowds: "We tested 104 out of 109 of the existing animals and found that the clear majority of them use tools spontaneously, " says Masuda. Rutz adds, "The results show that tool use is part of their natural behavioral repertoire, not an effect of captivity. In many ways, the skills of the Hawaiian crow are very similar to those of the New Caledonian crow, which my team has been exploring for over ten years, "the biologist sums up. display
This video documents the fascinating skills of Hawaiian crowds. Credit: NPG Press
The discovery of a second tool-eating species from the corvidae family has interesting implications for the evolution of this ability, the researchers say: "The Hawaiian and New Caledonian crow are only comparatively distantly related. Their last common ancestor lived about eleven million years ago. That's probably why the talent for using tools has developed independently, "says Rutz. "It stands out that both species live on remote tropical islands where woodpeckers are missing - apparently the conditions under which the intelligent crows become skilled tool users, " says the biologist.
Among the findings, even the famous chimpanzee behavioral scientist Jane Goodall, who discovered the tool behavior of chimpanzees in Africa, said: "It is wonderful to hear about the discovery of tool use in other species. Now we can compare this behavior in birds and primates, "said Goodall. "The discovery emphasizes the importance of preserving animal species - so we can learn about their behavior before it disappears forever." For the Hawaiian crow, hope is emerging: "By the end of the year, we will release captive Hawaiian crowds in Hawaii to re-establish a wild population, " Masuda announces.
Original work of the researchers:
- Nature, doi: 10.1038 / nature19103