Hawaiian crows wield tools

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A captive Hawaiian crow (‘Alalā) using a stick tool to extract food from a wooden log. ‘Alalā have relatively straight bills and highly mobile eyes – features that may aid their handling of bill-held tools.
Credit: Ken Bohn / San Diego Zoo Global

An extremely rare crow has become the second member of its family to demonstrate tool use, according to new research.

Christian Rutz from the University of St Andrews, UK and colleagues found the Hawaiian crow (Corvus hawaiiensis), or ‘Alalā, is smart enough to match the New Caledonian crow in its dexterous use of tools for foraging.

They published their work in Nature.

Species of crows and ravens number 40 across the world, but this family of birds remains poorly studied.

The New Caledonian crow’s singular skill was baffling to scientists, and a comparison species was needed to draw evolutionary conclusions about this interesting ability.

“We had previously noticed that New Caledonian crows have unusually straight bills, and wondered whether this may be an adaptation for holding tools, similar to humans’ opposable thumb,” Rutz explains.

A search for this trait in other crow species led him to his target: the ‘Alalā.

The ‘Alalā has been extinct in the wild since the early 2000s, but kept alive in captivity in limited numbers.

Incredibly, the team was able to conduct a species-wide study, surveying 104 of the 109 captive ‘Alalā for signs of tool use.

According to the findings, 78% of the birds tested showed spontaneous tool use, with higher numbers among fully grown crows.

Interestingly, the study also showed juvenile ‘Alalā demonstrated tool-use without any training or demonstration from their adult counterparts.

“Using tools comes naturally to ‘Alalā,” says Rutz. “These birds had no specific training prior to our study, yet most of them were incredibly skilled at handling stick tools, and even swiftly extracted bait from demanding tasks.

“In many regards, the ‘Alalā is very similar to the New Caledonian crow, which my team has been studying for over 10 years.”

The New Caledonian crow and the ‘Alalā are not closely related, but they have spent their crucial evolutionary years in similar environments. Both species are found on remote islands where they don’t have many predators or much competition for prey. 

This, the researchers hypothesise, may go some way to explaining their similar skill-sets.

“With their last common ancestor living around 11 million years ago, it seems safe to assume that their tool-using skills arose independently,” explains Rutz. 

“It is striking that both species evolved on remote tropical islands in the Pacific Ocean that lack woodpeckers and ferocious bird predators – perfect conditions, apparently, for smart crows to become accomplished tool users.” 

The study adds to a growing database of knowledge around tool use, which could eventually lead to a greater understanding of the evolution of this ability in primates.

Jane Goodall, who wrote the first detailed report into tool-use in primates, says the study represents an exciting development.

“I love learning about the discovery of tool use behaviours in other species of animals,” she says.

“This latest finding is especially wonderful. With two tool-using corvids, the well-known Galapagos finches, and one vulture in the list of tool-using birds, we can now make comparisons with avian and primate tool using.

“Each of these discoveries shows how much there is still to learn about animal behaviour, and it makes me re-think about the evolution of tool use in our own earliest ancestors.”

There is good news for the ‘Alalā, too – researchers at the San Diego Zoo Global’s Hawai‘i Endangered Bird Conservation Program are gearing up to release a population of the rare species back into the wild.

“Later this year, in collaboration with our partners, we will be releasing captive-reared ‘Alalā on Hawai‘i Island, to re-establish a wild population,” says Bryce Masuda, conservation program manager of the project and collaborator on the study.

Douglas Myers, chief of San Diego Zoo Global, says the research has been enlightening in terms of conservation, and he has high hopes for the species’ recovery.

“The discovery that ‘Alalā naturally use tools is of great significance, especially at this critical stage of our recovery efforts, as it provides completely unexpected insights into the species’ ecological needs,” Myers explains.

“After more than 20 years of hard work, we are finally ready to release birds. I am confident we will manage to bring this iconic Hawaiian bird species back from the brink of extinction.”

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