In New Caledonia, an island off the eastern coast of Australia, a crow is hunting for beetle grubs. The larvae are hidden within a decaying tree trunk, which might seem like an impregnable fortress. But the New Caledonian crow is smarter than the average bird. It uses a stick to probe the tunnels where the grubs are sheltered. The grubs bite at intruders with powerful jaws but here, that defensive reflex seals their fate; when they latch onto the stick, the crow pulls them out.
This technique is not easy. Birds need a lot of practice to pull it off and even veterans can spend a lot of time fishing out a single grub. The insects are fat, juicy and nutritious but do they really warrant the energy spent on extracting them? The answer is a resounding yes, according to Christian Rutz from the University of Oxford. By analysing feather and blood samples from individual crows, he found that grubs are so nutritious that just a few can satisfy a crow for a day.
You don’t have to be particularly intelligent to use tools – many animals do so, including some insects. But it takes a uniquely intelligent animal to be able to combine different tools to solve a problem. We can do it, the great apes can do it, and now the New Caledonian crow joins our exclusive club.
Animals can use tools using little more than pre-programmed behaviour patterns that require little intelligence. But combining tools, or using one tool on another (a metatool, if you will), is a different matter entirely – that takes reasoning. This type of intelligence has been the engine of human innovation. It allowed us to use simple tools to make advanced ones, or to combine different tools into increasingly complex machines.
The majority of animals lack the ability to manipulate tools in this way and in primates, the line is drawn at the great apes – they can (mostly) do it, but monkeys struggle. So it may come as a surprise that a humble bird has now been found to use metatools to the same standard as our ape cousins – the New Caledonian crow.
Of course, anyone familiar with the exploits of the New Caledonian crow probably won’t be surprised at all. These are no bird-brains; they are, in fact, strong contenders for the title of the most intelligent bird, and expert tool-makers to boot. Their ingenuity is most apparent when they are searching for food, converting twigs and branches into hooks and spears for dislodging juicy grubs from hollows in wood.
But while many birds do this, the crows are special. They can spontaneously make new tools from materials they have never seen before, like a hook from a bent wire. They have also been seen manufacturing new tools by altering existing ones and passing their newfound technology onto others, a ability even great apes aren’t known to have. Now, Alex Taylor and colleagues from the University of Auckland have found that they can use one tool on another in the quest for food.