New Caledonian Crow, the Only Tool Manufacturer in Animal Kingdom
We believe that human have superiority over other animals as our ancestors were able to manufacture and use tools and thus we become what we are today. However, scientists have found that “New Caledonian crows Corvus moneduloides have impressive tool manufacturing capabilities”, possessing a similar characteristic of early human tool manufacture.
How do these wild New Caledonian crows make tools, in particular, hook tools?
In a study by Gavin R. Hunt and Russell D. Gray, they observed an adult crow (three times) and its dependent offspring (seven times) manufacturing tools from small and leafy Cunonia vieillardii twigs to extract the food in the holes. For all 10 tools, the crows followed four basic steps. They (i) selected a fork formed by, usually, two twig; (ii) broke off one twig just above the junction (side twig) and discarded it; (iii) broke off the remaining twig just below the junction (tool twig); and (iv) carried out fine sculpting of the hook on the tool twig with the bill, in between removing the leaves.
The sculpting removed small pieces of wood from the hook, which refined and sharpened it. Both crows took a significantly longer time to complete the last step. It is highly possible that the crows’ goal was to manufacture the hooked tools since they carried out this complex process routinely and most of the time they used the hooked ends as working ends while foraging.
The differences in the behaviour of the two crows suggested that the juvenile was less experienced than its parent at making and using hooked twigs. Thus, tool manufacture should be a learning process that is passed on from one generation to the next. The juvenile learned this skill from its parent since tools allowed them to reach food resources more easily, increasing their fitness.
“Future work needs to address the question of why this particular species of crow can make such sophisticated tools when neither its close avian relatives, nor our primate cousins, appear able to do so.” The authors concluded.
(Reference: Gavin R. Hunt & Russell D. Gray, 2004. The crafting of hook tools by wild New Caledonian crows (Corvus moneduloides). Proceedings B, 271(3): 88-90 )
(Related article: “Nurturing Nests Lift These Birds to a Higher Perch,” by NATALIE ANGIER, 31 January 2011. URL: http://www.nytimes.com/2011/02/01/science/01angier.html?pagewanted=all&_r=1& (accessed on 29 Mar 2013) )