What makes a good tool user? A species-wide experimental study of the Hawaiian crow

Tool use is extremely rare across the animal kingdom. The behaviour has been observed in less than 0.01% of all species, and only a handful of these use tools on a daily basis or are capable of manufacturing tools from raw materials. This presents a major scientific puzzle, given that tool use can afford significant benefits, for example, by providing easy access to nutritious out-of-reach food. In this project, we want to address this conundrum by posing a seemingly simple question: "What makes a good tool user?"

Two key ingredients are needed to address this question: a suitable study species and an appropriate research strategy. Rather than working with one of the well-known tool users, like chimpanzees or New Caledonian crows, we propose to study the Hawaiian crow (usually called 'Alala) -- a species whose tool-using abilities were discovered and systematically documented only a couple of years ago. The species sadly became extinct in the wild in 2002, but survives in two captive facilities in Hawaii where our collaborators are breeding birds for an ongoing reintroduction programme. Having access to all adult members of a species, of known genetic and social background, offers an outstanding research opportunity.

With regard to the research strategy, we first need to document how individuals vary in their ability to use, make and invent tools ('technical competency'). We know from our earlier observations that some 'Alala are highly skilled tool users, while others are quite clumsy, or do not use tools at all. To study these differences systematically, we have designed tasks that measure either how fast birds can extract food with tools, or how flexible and inventive they are -- two complementary facets of being a good tool user. For instance, some of our tasks involve using a stick to extract small pieces of food from holes of increasing difficulty, modifying raw materials to create a functional tool, or inventing an entirely new tool type.

The next step involves searching for factors that may explain variation in birds' technical competency. We will collect two additional datasets for this purpose. First, we will test our subjects on tasks that assess -- without requiring the use of tools -- various cognitive and behavioural capacities. For example, we have included tasks measuring memory ability, learning speed, innovation tendency, problem-solving persistence, and attraction to novel objects. This will help us determine whether birds that are 'smarter' overall, or have particular behavioural dispositions, are better tool users. Second, we will collect extensive 'personal' information on the birds, including their age, rearing history, relatedness to other individuals, and even their morphology. This is because 'Alala may hone their tool-using skills as they get older, learn by observing tool-proficient adults, inherit technical competency from their parents, or benefit from having particularly straight bills that allow dexterous handling of sticks and raw materials. Once both of these large datasets have been collected, we will combine all information and use advanced statistical techniques to examine what makes a good tool user.

In summary, we will use the most comprehensive set of experimental tasks ever developed for investigating animal tool use, collecting data for an entire species. A study of this scale is unprecedented and has the potential to produce a step change in our understanding of what is special about making and using tools. Importantly, our detailed investigation of behavioural variation across individual 'Alala will contribute to uncovering why tool use is so rare across the animal kingdom, and it may even shed new light on how humans have evolved their astonishing technological prowess.

The striking phylogenetic rarity of tool behaviour continues to attract considerable research attention. In search for the behaviour's possible evolutionary drivers, and its cognitive underpinnings, researchers are conducting detailed comparative analyses, both across taxa and for selected, phylogenetically-matched species pairs. While this work is bearing fruit, revealing glimpses of what is special about this fascinating behavioural adaptation, progress is inevitably slow, given that only a relatively small number of species is available for assessment. A complementary approach, which remains surprisingly underused, is to investigate behavioural variation within species. Using the Hawaiian crow as a model system, our project asks a deceptively simple question: "What makes a good tool user?" In other words, we aim to understand why some individuals excel at using, making and inventing tools ('technical competency'), while others are relatively inept, or do not use tools at all. We will address this question by pursuing three inter-related research objectives, namely: to run the world's entire adult 'Alala population (~105 birds) on an extensive, newly-developed behavioural test battery, measuring aspects of the birds' technical competency, cognitive performance and general behavioural disposition (18 metrics); to collect a wide range of other phenotypic information for our test subjects, including sex, age, body size, genetic relatedness, social background and reproductive performance (9 metrics); and to identify factors associated with 'Alala's technical competency, using advanced statistical modelling techniques. Our project will provide the most comprehensive single-study investigation to date of tool behaviour in a non-human animal. Importantly, its innovative experimental approach will generate testable predictions applicable to other species, providing new impetus for broader taxonomic comparisons that attempt to uncover why so few animal species use tools.

We have identified three main groups of non-academic beneficiaries of our proposed research:

GENERAL PUBLIC
Humans feel a real sense of awe when they see other animals using tools. This fascination stems from an awareness that tool use is a rare skill, and that we are particularly good at it -- on an intuitive level, we know that the topic is key to understanding what it is that makes us 'human'. As explained in the Lay Summary, we will shed light on these deep issues with one of the most comprehensive studies of non-human tool behaviour ever conducted, providing excellent opportunities for effective public engagement. Our outreach strategy is: to prepare regular press releases to generate international media interest; to showcase our research at a well-established science exhibition in the UK; and to give public lectures in both the UK and Hawaii. The PI's team has an excellent track record of communicating their research on tool-using crows via these routes, and will collaborate closely on this new project with San Diego Zoo Global (SDZG), who not only have an extensive network of contacts in Hawaii but also enjoy support from a well-funded, professional PR department.

CONSERVATION PRACTITIONERS
Our proposed project has potentially important implications for ongoing efforts to bring the 'Alala back from the brink of extinction. Very little is currently known about the species' general behavioural repertoire, despite desperate attempts in the 1990s to gather as much information as possible before its extinction in the wild. Our comprehensive behavioural test battery will produce a transformational advance in our understanding of these birds, generating data on their technical competency, cognitive performance and general behavioural disposition. We will leverage these datasets to make contributions to ongoing efforts to propagate the species in captivity, and to reintroduce it back into the wild. Specifically, we will: make recommendations for how to improve husbandry and enrichment regimes at the two captive breeding facilities; help managers identify individuals that exhibit desirable behavioural traits for captive breeding and/or release; and develop protocols for conditioning immature birds prior to release, to ensure their behavioural competency. We will ensure that these valuable non-academic outputs reach their intended end-users: by holding annual personal meetings with the SDZG team that runs the captive breeding facilities; by presenting findings to the multi-stakeholder 'Alala Working Group (AWG); by visiting SDZG's Recovery Ecology Unit in San Diego; and by preparing a written report with formal recommendations for SDZG and the AWG. Finally, we hope that our project will deliver substantial indirect benefits for SDZG and its associates, who work tirelessly to save the 'Alala. By uncovering the cognitive capacities of this critically-endangered species, and raising its international profile, our project may generate new funding opportunities and foster continued public and political support for this ambitious species recovery programme.

NATIVE HAWAIIAN COMMUNITIES
The 'Alala is revered by native Hawaiian communities as an 'aumakua (family god), features heavily in local folklore and was once kept by kings as a ceremonial pet. Our research can make valuable contributions to nurturing cultural interest in the species, and to generating wider societal discourse about the non-economic value of wildlife. With help from our well-connected SDZG Project Partners, we will reach out to, and engage with, native Hawaiian communities. We will achieve this goal by inviting local groups to our public lectures in Hawaii, which will in turn generate opportunities for longer-term engagement. The PI has built strong relationships with indigenous communities in New Caledonia through similar activities.