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Research to crow about

Interview: Dr Christian Rutz (University of St Andrews)…

Research to crow about

Research to crow about

Dr Christian Rutz is a Reader in the School of Biology at the University of St Andrews. His research group studies one of the most remarkable animal tool users – the New Caledonian crow. Living on a remote tropical island, these birds use sticks and pieces of leaves to forage for nutritious grubs and other hidden prey, exhibiting a degree of technological sophistication which rivals even that observed in our closest relatives, the chimpanzees. In the course of his field study, which recently celebrated its tenth anniversary, Rutz and his team have developed a range of innovative technologies, including bird-mounted miniature video cameras and proximity loggers, which enable the researchers to remotely document the foraging behaviour and social interactions of these shy forest birds...

They are not an endangered species and they live on  the opposite side of the world from St Andrews, but New Caledonian crows are the focus of one of the most innovative ornithological field studies ever conducted – and one of the animal kingdom’s most ingenious users of tools. Dr Christian Rutz and his research group at the University of St Andrews are leading the way in trying to explain the crows’ remarkable behaviour, using some ingenious tools of their own, including tiny video cameras, or ‘crowcams,’ so small (weighing less than a £2 coin) that they can be attached to the tails of the birds, providing a crow's-eye view of their use of foraging tools, without restricting the birds’ natural behaviour.

According to Rutz, New Caledonian crows provide one of the most interesting examples of tool use among birds and mammals, not least because they are the only animals apart from humans that naturally manufacture ‘hook-shaped’ tools. Other birds also use tools – for example, woodpecker finches, Egyptian vultures and palm cockatoos – but New Caledonian crows have “a much more diverse tool repertoire,” using at least three different tool types, multiple variations of the basic designs. The crows use their tools to extract invertebrate prey from rotting timber and vegetation, and Rutz believes they may use particular tool types or design variants for specific foraging tasks, similar to humans using different tools for different jobs.

The big mystery is why so few animal species use tools to start with. “We know that tools are useful,” Rutz explains, “yet very few animals use them. So, why?” Apart from improving our understanding of New Caledonian crows, as a particularly interesting case study, Rutz hopes that in the longer term his research will provide new perspectives on the evolution of animal tool behaviour more generally, and ultimately shed fresh light on the remarkable sophistication of human technology.

One major challenge is to understand the specific function of tool use, and to document what components of the crows’ diet are obtained by using tools. Recent research by Rutz’s team suggests that prey obtained with tools is important for raising their young. “Perhaps crows that are good tool users raise more, or healthier, chicks,” Rutz speculates. “Studying the energetics of animal tool use can provide insights into the ecological conditions under which this rare behaviour can evolve.”

Rutz is very careful not to make the assumption that tool use – or technological skill – is the same thing as intelligence. Chimpanzees or crows may not build space shuttles or televisions, but Rutz is more concerned with simply understanding the evolutionary processes which lead to the development of rudimentary tool behaviour. Tool use is also relative to individual needs and conditions; for example, in many foraging situations, a simple stick or an unmodified stone tool will suffice. There are also many interesting examples of invertebrate tool use: hermit crabs protect themselves with shells and some spiders carry around their webs and actively cast them over unsuspecting prey. “These examples challenge the notionthat big brains, and advanced levels of intelligence, are required for tool behaviour,” Rutz cautions.

Accordingly, when it comes to the crows’ cognitive abilities, Rutz describes himself as an agnostic. “These birds clearly do impressive things with their tools, but controlled experiments are required to establish what exactly they ‘understand’ about the underlying physical principles.”

Mainstream ecology

So how did Rutz get interested in this particular species? Like many other scientists, serendipity played a big role in choosing what direction to take in his future career. “For my PhD, I studied the foraging ecology and population dynamics of northern goshawks,” says Rutz. “This was ‘mainstream’ ecological research. At the time, two friends of mine were studying captive New Caledonian crows for their PhDs, and we started collaborating. Having seen these crows use tools in captivity, I immediately started wondering about the ecological conditions on their home island. And I simply had to go there, to see for myself.”

After completing his DPhil Thesis at Oxford in 2005, Rutz launched his field project on New Caledonian crows as a Junior Research Fellow. In 2009, he was awarded a prestigious BBSRC David Phillips Fellowship, worth almost £1.5 million, which enabled him to set up his independent research group at Oxford and to expand the scope of his crow project. Three years later, Rutz and his team moved to the University of St Andrews, a world leader in the fields of animal social learning, culture and tool use, and this offered lots of opportunities for exchange and collaboration. Within months of their arrival, several new collaborations were forged. The team now conducts fieldwork in seven study sites across the island, covering a range of different crow habitats.

In some study populations, about 80–90% of the resident crows have been marked with colour rings and wing-tags, enabling field workers to document the behaviours and life histories of individual birds. Rutz does not like ‘naming’ his subjects, however, since this may unconsciously bias observations. For example, if the birds were called 'Marie Curie' or ‘Albert Einstein,’ because they had excelled at certain tasks, observers may expect to see unusual behaviours, but this is not the case if neutral codes (e.g., 'ER4') are used.

New Caledonian crows are naturally shy, and even in areas where they have been habituated to the presence of humans, data collection is not easy – they enjoy observing their observers. They also live in difficult terrain (tropical forests on very steep slopes), so following and watching them can be a challenge. “During an early brainstorming session,” explains Rutz, “we thought it would be great if we could see exactly what the crow sees, and the idea of using miniature crow-mounted video cameras was born.” Suitable systems were not available at the time, so Rutz’s team took on the challenge of designing their own cameras.

In describing how the cameras were developed, Rutz stresses the importance of lateral thinking and interdisciplinary skills. “I enjoy reading very broadly, exploring seemingly unconnected literatures,” he says, “as well as unconventional methodologies.” Sometimes, when he spots an exciting connection, these insights lead to new discoveries about his study system. Miniature video cameras have since been used by other teams on a wide range of other bird species and are quickly becoming part of field ornithology’s basic tool kit. More recently, Rutz used cutting-edge wireless sensor network technology to chart the social dynamics in one of his crow populations. “These ‘proximity loggers’ enabled us to record remotely who meets whom,” he explains. “It was a bit like looking at human friendship networks on Facebook or Twitter.” Rutz’s pioneering contributions in this area have been recognised with several awards and prizes.

The mission

So what does Rutz hope to achieve with his study? How long will his project continue?  And what will constitute ‘success’ for his research?

“My ambition is to chart the ecological conditions under which tool use is profitable for these birds,” Rutz explains. “Once we understand their foraging ecology, we can make cautious inferences about the evolutionary origins of their unusual tool behaviour.”

The unique conditions in New Caledonia have enabled something special to develop, ever since crows first arrived on the island several million years ago. According to Rutz, the use of tools evolved over time, as crows discovered novel foraging opportunities and potential tool materials. One big advantage for New Caledonian crows is that they have no major predators, so they can concentrate harder on what they are doing. Or as Rutz says: “They have plenty of time on their hands.” It sometimes takes crows several minutes to manufacture a satisfactory tool, and even more time to extract prey from tree holes or from behind bark – activities which demand the birds’ full attention. There are also no primates or woodpeckers on this remote island that might compete for similar embedded foods. Rutz explains: “These crows have essentially filled a ‘woodpecker niche’, but instead of using their bills to extract insects from timber, they use tools.”

The last common ancestor of crows and humans would have lived about 310 million years ago (170 million generations), while other primate tool users, such as chimpanzees, only ”split from the human lineage” about six million years ago (250,000 generations). Tool behaviour in humans and crows must have evolved independently, and Rutz notes that this independence of origin provides an opportunity to search for commonalities. In a sense, crows may provide a window into our own evolutionary past, and help explain how rudimentary tool use may arise. “We may learn a lot through these comparisons,” says Rutz, “but we should also be cautious. After all, New Caledonian crows manufacture stick tools, not supercomputers.”

At the same time, Rutz rejects out-dated thinking that ranks animals according to their technical skills, with humans sitting at the top of the tree.

Rutz expects to spend the rest of his career studying New Caledonian crows. Their tool behaviour was first described in print in the early 20th Century, but a lot of research remains to be done. Hard fieldwork has provided important insights into the species’ natural history, and is now paving the way for tackling some particularly exciting objectives. “We recently discovered that crows in one of our study populations make very complex hook-shaped tools, and we are keen to investigate what these are used for,” says Rutz. Hook making was a key innovation in early humans, and New Caledonian crows offer unique opportunities to examine  the evolutionary and ecological context of this very special capacity.

“I think I am quite good at spotting opportunities,” says Rutz, but the miniature cameras are only a small hint of what he still hopes to achieve. One future project, for example, may examine laterality in New Caledonian crows’ tool handling – the birds hold their stick tools in their bills and are either ‘right-cheeked’ or ‘left-cheeked’. This work will be carried out in collaboration with biomedical scientist Dr Silvia Paracchini, another member of the Young Academy of Scotland who is also based at St Andrews.

Explaining crow behaviour may seem like an unusual approach to understanding humans, but Rutz hopes to “establish the New Caledonian crow as a useful model system to shed light on the mysteries of human evolution and, along the way, pioneer new research methodologies.” Maybe crows and humans have much more in common than we used to believe...


Call to action

Over the last ten years, Dr Christian Rutz has established a solid foundation – both scientifically and logistically – for a world-leading, long-term research project. To consolidate and expand his research activities, he has now decided to set up a permanent research station on the west coast of New Caledonia, close to several of his most intensively studied crow populations. The station will provide sleeping and living quarters for up to ten fieldworkers, a lab for processing biological samples and data, and aviaries for housing birds, for the brief duration of behavioural experiments. Since conventional funding sources do not support this kind of capital overseas investment, Rutz is seeking philanthropic support for his ambitious initiative. Once one or two principal donors have been found, the station will be named in their honour. An indigenous tribe has already promised to donate land in a prime location, and the local authorities have confirmed their long-term support for the project. A research station would enable Rutz’s team to intensify their research efforts, especially by collecting data year-round, rather than during comparatively brief, annual expeditions. Rutz has worked closely with diverse New Caledonian communities over the years and sees an opportunity to develop these relationships further; for example, by setting up a local field assistant scheme. While the focus will remain on studying New Caledonian crows, Rutz hopes that, ultimately, he will be able to host other international research groups, to facilitate broader exploration of the island’s remarkable fauna and flora.





"Research to crow about". Science Scotland (Issue Eighteen)
Printed from on 03/04/20 11:15:36 AM

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