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Tropical crow species is highly skilled tool user

Copyright: Ken Bohn/San Diego Zoo Global
News from: University of St Andrews

An international team of scientists and conservation experts has discovered that the critically-endangered Hawaiian crow, or ‘Alalā, is a highly proficient tool user, according to a paper published in Nature.


For decades, another species – the famed New Caledonian crow – has baffled researchers with its remarkable tool-using skills. These birds, which only live on the remote South Pacific island of New Caledonia, use tools to winkle insects and other prey from deadwood and vegetation, exhibiting an astonishing degree of dexterity. The big question was why they, but apparently no other members of the crow family (corvids), had evolved such technological prowess.

There are over 40 species of crows and ravens in the world, and many of them – especially those living in remote tropical locations – remain poorly studied. “This raises the intriguing possibility that there are some undiscovered tool users out there,” explains the study’s lead scientist, Dr Christian Rutz, from the University of St Andrews, UK. His work is funded by a BBSRC David Phillips Fellowship, which provides support for researchers who have shown high potential to establish their first independent research group.

“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,” says Rutz. By searching for this tell-tale sign amongst some of the lesser-known corvid species, he quickly homed in on a particularly promising candidate for further investigation – the ‘Alalā.

Following a population crash in the late 20th century, the ‘Alalā is now extinct in the wild. In a last-ditch effort to preserve the species, the remaining wild birds were brought into a captive breeding programme. “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, co-leader of the study and Conservation Program Manager of San Diego Zoo Global’s Hawai‘i Endangered Bird Conservation Program.

Masuda was excited when the St Andrews scientists got in touch with his team: “We had occasionally seen birds using stick tools at our two breeding facilities, but hadn’t thought much of it.” The St Andrews and San Diego teams quickly agreed to conduct a collaborative project, to examine the tool-using skills of ‘Alalā under controlled conditions.

“We tested 104 of the 109 ‘Alalā alive at the time, and found that the vast majority of them spontaneously used tools,” says Masuda. Current evidence strongly suggests that tool use is part of the species’ natural behavioural repertoire, rather than being a quirk that arose in captivity, according to Rutz: “Using tools comes naturally to ‘Alalā. 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.”

Experts have applauded the ‘tour de force’ of controlled experiments. “Most studies in our field investigate just a handful of subjects, so it is truly mindboggling to see an entire species tested,” comments Professor Thomas Bugnyar, a corvid expert at the University of Vienna, Austria, who was not involved in the study.

The discovery of a second tool-using crow species finally provides leverage for addressing long- standing questions about the evolution and fundamental bioscience of animal tool behaviour. “As crow species go, the ‘Alalā and the New Caledonian crow are only very distantly related. 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.

According to Douglas Myers, President and Chief Executive Officer of San Diego Zoo Global, the study marks an important milestone for the long-running ‘Alalā recovery programme: “This is a wonderful example of how scientific research can contribute to conservation efforts. 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. 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.”

Reference: Discovery of species-wide tool use in the Hawaiian crow. Nature 537, 403–407.



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The critically endangered Hawaiian crow is a highly proficient tool user

About the University of St Andrews

Founded over 600 years ago, the University of St Andrews is the third-oldest university in the English-speaking world. It is consistently ranked amongst the UK’s top universities, together with Oxford and Cambridge. Dr Rutz’s research group, which studies the ecology and evolution of tool use in non-human animals, is based at the Centre for Biological Diversity, in the School of Biology.

The study was funded by a grant from the UK’s Biotechnology and Biological Sciences Research Council (BBSRC), held by Dr Rutz at the University of St Andrews; he was one of only a handful of early-career scientists to be awarded a prestigious BBSRC David Phillips Research Fellowship in 2009. Funding for the captive ‘Alalā propagation programme was provided by the U.S. Fish and Wildlife Service, Hawai‘i Division of Forestry and Wildlife, Moore Family Foundation, Marisla Foundation, several anonymous donors, and San Diego Zoo Global.

Photos and videos of birds, and other media materials, are available from the press offices of the two lead institutions, please see external contact information below.

The two lead authors are available for interviews (phone, Skype, radio, and TV; ISDN line and live TV link available), and members of the research team can provide assistance in a wide range of languages (including English, German, French, Japanese, Swahili, Dutch, Danish, Swedish and Finnish):

Tags: animal behaviour birds image gallery University of St Andrews press release video