Another species of crow uses tools

September 21, 2016 • 8:30 am

The definition of “tool use” in animals is a bit controversial, depending as it does on whether the object is modified before it’s used as a tool. In its list of animal tool use, Wikpedia gives a widely-used definition proposed by Shumaker, Walkup, and Beck in their 2011 book Animal Tool Behavior: The Use and Manufacture of Tools by Animals:

“The external employment of an unattached or manipulable attached environmental object to alter more efficiently the form, position, or condition of another object, another organism, or the user itself, when the user holds and directly manipulates the tool during or prior to use and is responsible for the proper and effective orientation of the tool.”

And, according to the Wiki article, tools use is seen in 33 families of birds, including these (I have a video for each example):

There are many more examples, although the authors of the paper we’re discussing today say that “only a handful of bird species are known to use foraging tools in the wild.” It is true that some bird “tool use” has been described only in captive birds, but the Wikipedia article suggests that tool use in nature is seen in more than a “handful” of birds.

Now I’m not sure how important the distinction between “use in the wild” and “use in nature” is: in both cases, animals can either be hard-wired to use tools, or learn it from other individuals who have figured it out themselves. And regardless of whether it’s seen in captivity or the wild, it tells us something about the creativity and intelligence of animals. I suppose biologists are more interested in “natural” behavior rather than behavior in captivity, perhaps because of the possibility that humans rather than other animals could teach it. But biologists are far more fascinated by what goes on in the wild rather than what happens in zoos. For things like mating behavior that’s important, but not so much for tool use.

Regardless, any example of tool use by animals gets attention, like that described in a new paper in Nature by Christian Rutz et al. (free link and download below).  Sadly, not only is the behavior seen only in captivity, but it can only be seen in captivity because the species that uses tools is extinct in the wild. Yes, it’s the Hawaiian crow, the ‘Alalā (Corvus hawaiiensis), once endemic to the Big Island but driven to extinction in the wild by the depredations of mongeese (is that the right plural?), rats, and feral cats. The birds now live only in captivity, and are being bred for eventual release. There are 109 of them in three Hawaiian facilities, and one lonely individual off exhibit at the San Diego Zoo Safari Park.

Here’s an ‘Alalā; they’re handsome birds and, being corvids, are very smart:


The authors examined 104 of the existing 109 individuals, and found that 78% of them spontaneously used tools (mostly twigs) to probe for, spear and dislodge food items lodged in an experimental log riddled with holes and crevices. Here’s what the behavior looks like, and you can see it in the movie right below the figure:

(From paper): a, Captive birds using stick tools to extract bait from experimental logs

The New Caledonian crow, Corvus moneduloides, was already known to not only use tools, but solve all kinds of puzzles (see my previous posts here, here, and here); and they may even have a “theory of mind.” C. moneduloides is known to use tools in the wild, but it’s not possible at present to determine whether this is the case for the ‘Alalā.

The observation of tool use raises five questions:

How many times did this behavior originate among those 108 captive crows?  Since they’re caged and kept together (with historical records) as part of the breeding program, the authors determined that, if the behavior was learned and copied, it could have originated between 1 and 8 times. The authors favor the “more than one” number, saying that “it’s unlikely that a single ‘innovation’ event can explain the observed species-wide distribution of tool competence.” Well, to each their own, but those data themselves don’t militate in favor of multiple origins. The next point, however, does:

Is the behavior learned from others, or can it develop in single individuals? Clearly, the behavior, even if learned from others, had to start with at least one individual, so the question is a bit of a red herring. Nevertheless, it bears on how many times it can “originate” in both captivity and the wild. (A more important question, which can’t be answered in any way I can see, is whether there is a genetic propensity to use tools per se, or whether the birds are just fast learners for everything, and hit on tools as handy ways to get food.)

At any rate, the authors examined seven naive crows reared in two groups without ever having seen tool-using adults. All seven birds eventually started probing the holes and crevices with sticks, though only five were ultimately successful. But again, this is only two independent origins, not five.

Did this behavior occur in the wild? We don’t know, of course, but the authors make a case that when the ‘Alalā did live freely, they probably used tools. This is based on two observations: that juveniles spontaneously hit on using sticks to get food (fairly convincing), and that tool-using can be found throughout the whole species in captivity (not so convincing). They do note that before the species became extinct in the wild in 2002, there were no observations of tool-using by wild individuals, though they did forage on branches and trunks for insects.  As I said, though, I find the observation of tool use fascinating regardless of whether it’s seen in nature.

Did tool use in Caledonian and Hawaiian crows arise independently? Almost certainly, for the ‘Alalā and New Caledonian crows are distantly related, and no species in between shows the behavior. It’s thus unlikely that it was inherited in the two tool-users, either genetically or culturally, from a common ancestor. Here’s the phylogeny shown in the paper, along with a map and some other tool-users.



Finally, why did this behavior appear only in those two species of crow? Well, crows are smart, so they’re already prone to develop behaviors like this, especially given their even more remarkable ability to solve complex puzzles. The authors suggest this explanation for tool use in these two species:

As for possible ecological drivers, both species—as well as the stick-tool-using Galápagos woodpecker finch—evolved on remote tropical islands (Fig. 1e ABOVE) where competition for embedded prey is likely to be reduced and predation risk low. These conditions, which have previously been predicted to facilitate tool behaviour, may vary across island environments, but are presumably less common on adjacent mainland habitats, providing a possible explanation for the striking rarity of avian tool use.

Predation doesn’t seem that important to me, and it’s not clear what the authors mean: does using sticks make you more susceptible to being eaten? What seems more important is the lack of competition, especially woodpeckers, which are absent on the Galápagos, New Caledonia, and Hawaii. Woodpeckers are more efficient at getting prey than these crows (woodpeckers don’t, for instance, have to find a tool), and could very well outcompete the crows in foraging for insects in and on trees.

This could of course be tested if other crow species are found on islands lacking woodpeckers and other birds who can extract food from trees without tools, but it would require a large sample of unrelated crows, and I don’t know if we have that. What we have is yet another example of tool use in birds, the second in crows, and an observation that young crows can pick it up spontaneously. I don’t know if that merits a Nature paper, though it’s certainly worth reporting. Underlying all the publicity is the fact that tool use is fascinating to humans because we’re an anthropomorphic species.

h/t: Nicole Reggia, Trevor Price


Rutz, C., B. C. Klump, L. Komarczyk, R. Leighton, J. Kramer, S. Wischnewski, S. Sugasawa, M. B. Morrissey, R. James, J. J. H. St Clair, R. A. Switzer, and B. M. Masuda. 2016. Discovery of species-wide tool use in the Hawaiian crow. Nature 537:403-407.

19 thoughts on “Another species of crow uses tools

  1. Regarding the plural of mongoose, the “correct” plural is mongooses, but alternatives appear in some dictionaries, including the online OED, which gives (irreg.) mongeese, (irreg.) mongoose, (irreg.) mongooze.

    I am a personal fan of mongeese, as I am of the incorrect octopodes and kleenices.

  2. Predation doesn’t seem that important to me, and it’s not clear what the authors mean: does using sticks make you more susceptible to being eaten?

    Just blue-skying here, but a lack of predation threat could allow slower and more stationary food-getting strategies to work better. When there’s a hawk or cat in the area, sitting still on a log for five minutes to get a grub is not a viable strategy for feeding yourself. When there’s no hawks or cats around, it is.

    That’s my guess, anyway.

    1. There are native birds of prey (but no predatory mammals) on both Hawaii and New Caledonia, so lack of avian prdators seems an unlikely explanation for corvid tool-use on these islands.

    2. What came to my mind was what about the crows’ prey itself. Are the common prey items a bit more scarce or a bit harder to retrieve in the two species’ habitats, at least compared to other corvids? If other corvids have an easier access to common food items, they may not need to fashion tools to extract more difficult items that they would otherwise have to eat, even though they are all fairly intelligent themselves. American crows don’t seem to have to work that hard for food, nor, really, do ravens, who are carcass feeders, so they haven’t the need to get too technical in food acquisition, but what about the Alala or the New Caledonian? I don’t know much about their feeding habits or preferred food items, so it’s really just a wild-ass guess on my part, for what it’s worth.

  3. I have sen many videos of crows using tools, as in much of the above video but I have never seen “hunting” cooperation between crows depicted above. A crow remarkably offered a tool for another to use. However, being a fully paid up crow and therefore crafty, it made of with the stolen loot.

  4. Two crow observations:
    – saw a fox catch a crow from a flock on the ground, and the rest of them followed and harassed that fox everywhere he went for the rest of the summer.
    – Our adopted-as-adult “res dog” hates crows; they’ll fly down low to encourage him to chase them…over the edge of a cliff.

      1. The res-d*g (blog standard?) is damned smart (guessing 3/4th border collie + something mean and stocky) but our dumb dog would run along with him and neither ever went over the cliffs. This was around Monument Valley/Goose Necks Park where 30-50′ vertical cliffs in the middle of nothing were common.

        Back to the OP, tho, the crows would build nests on rocks jutting from the canyon walls, often under another overhang.

  5. Thanks, very interesting.

    Crows (and their kin) are always of great interest to me.

    We used to have a lake cabin in northern Minnesota. When I was a youth, I noticed that the crows would sit when I walked around the area. However, if I took one step outside the door with a gun (or even something that slightly resembled a gun) would cause the crows to instantly disappear.

    Clever corvids …

  6. Corvids are astonishing. My grandfather used to insist that there was even one who lived near him who had learned to repeat the phrase “bugger off” or something like that. Dunno if that’s just a crazy story from a then old man, but …

  7. The New Caledonia crow is so smart, but they’ve chosen as their national bird the kagu. They’re almost extinct because they’re so stupid they cover their heads with their wings when danger threatens. Another example of faith being elevated over genuine smarts?

  8. I like corvids in general, but my favorite species is the grey jay [Perisoreus Canadensis] — I’ve always loved giving hand-ups of food to the flocks at camp shelters and scenic overlooks along X-country ski trails in the Cascades of Oregon and Washington.

    When I see them in the summer, it’s individuals, not flocks, and they don’t follow or beg [mostly — there’s a roadside stop with a grand view of Mount Rainier that seems to have year-round jay grifting.

    A couple of weeks ago I spent a few days in a very unpopulated area of British Columbia. Again saw grey jays just doing their thing with little regard to our party. Then we took the road up to a very isolated ski area — with no other people around and probably no visitation at all until ski season started. Within five minutes, we were treated to a conveyor belt of jays — probably 8-10 lined up politely [to each other] to take our lunch treats out of our hands.

    Question is — did this flock of jays learn the courteous begging only when the ski area went in? And is this behavior independently arrived at everywhere that recreationists and tourists stop for lunch? Or was there a wandering jay prophet telling its people to worship at the altar of Goretex and daypack?

  9. Anybody choosing to visit San Diego who has an interest in wild animals, I would recommend visiting the San Diego Safari Park. The animals are allowed to roam free (no zoo like enclosures) within the park while the tourists are enclosed in buses which tour the park for close up views of the animals behaving naturally. (Predators and prey are kept apart and they are all well fed).

    The San Diego Zoo itself (within the city) is also worth a visit. The animals (for the most part) are kept in open environments resembling their natural habitats, built within deep pits which visitors overlook. Because of the mild winters it is not necessary to move animals indoors to shelter them from the elements.

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