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.
In the Goualougo Triangle of the Republic of Congo, a chimpanzee is hungry for termites. Its prey lives within fortress-like nests, but the chimp knows how to infiltrate these. It plucks the stem from a nearby arrowroot plant and clips any leaves away with its teeth, leaving behind a trimmed, flexible stick that it uses to “fish” for termites.
Many chimps throughout Africa have learned to build these fishing-sticks. They insert them into termite nests as bait, and pull out any soldier termites that bite onto it. But the Goualougo chimps do something special. They deliberately fray the ends of their fishing sticks by running them through their teeth or pulling away separate fibres – just watch the chimp on the right in the video below.
The result is a stick with a brush-like tip, which is far more effective at gathering termites than the standard model. This population of chimps has modified the typical design of the fishing stick to turn it into a better tool. They truly are intelligent designers.
From the carpenter choosing the right strength of drill, or the artist selecting the right weight of pencil, humans have a natural talent for picking the right tool for the job. Now, it seems that monkeys are similarly selective about their tools. In the first study of its kind, Elisabetta Visalberghi from the National Research Council, Italy, found that capuchin monkeys are able to pick stones with the right properties for nutcracking.
Capuchins often use stones to crack otherwise impenetrable nuts upon hard, flat surfaces, turning innocuous forest objects into their own hammers and anvils. By examining their cracking sites, Visalberghi deduced that the animals were picky about their hammers, for the sites were littered with hard and heavy rocks that weighed as much as 40% of an adult. However, it was entirely possible that the monkeys used any old rocks and those that remained were simply the ones that hadn’t eroded yet.
Visalberghi decided to put eight wild capuchins to the test by allowing them to choose between sets of potential hammers. These monkeys regularly use stones to break into palm nuts and they need heavy, hard materials for the job. Visalberghi removed all the stones from the experimental arena and provided the capuchins with a choice of two – one of which would excel as a nutcracker and another which would not. The monkeys selected the right stone at least 90% of the time, correctly picking solid siltstone over crumbly sandstone, and big quartzile stones over small ones.
In both cases, the stones were natural ones of the type that the monkeys regularly encounter in their habitat. No surprise then that the animals immediately and confidently singled out the right tool. But Visalberghi found that they did just as well when choosing between artificial stones – they just spent more time examining the different options on offer.
In Shark Bay, off the Western coast of Australia, a unique population of bottlenose dolphins have a unusual trick up their flippers. Some of the females have learned to use sponges in their search for food, holding them on the ends of their snouts as they rummage through the ocean floor.
To Janet Mann at Georgetown University, the sponging dolphins provided an excellent opportunity to study how wild animals use tools. Sponging is a very special case of tool use – it is unique to Shark Bay’s dolphins and even there, only about one in nine individuals do it. The vast majority of them are female. A genetic analysis revealed that the technique passes down almost exclusively from mother to daughter, and was invented relatively recently by a single female dolphin, playfully named “Sponging Eve”.
Dolphins tend to sponge only in deep water, which is why little has been done to study this behaviour since its discovery a decade ago. Now, Mann has published the first detailed analysis of dolphin sponging. She watched every dolphin who knows the technique and analysed how much time they spent on it and what it meant for their success at raising calves. This incredibly thorough analysis revealed that sponging dolphins are the most intense tool-users of any animal, except for humans.
Mann confirmed that the dolphins were using the sponges to root out potential meals. On days when the sea was exceptionally clear, she could see the animals swimming slowly along the sandy bottom while wearing their spongy muzzles and disturbing the sand. When they spotted something, they dropped the sponge and probed about with their beaks, often surfacing with small fish that they quickly swallowed. Meal in throat, they retrieved their unusual hunting aid and started again.
The technique worked for humans too. Mann’s team tried it themselves for four hours with sponges over their hands, and consistently ferreted out the same species of fish – the spothead grubfish. Before the sponges were used, the fish were completely invisible to the divers but once revealed, they were easily spotted, tracked and found again when they reburied themselves. A single photo of a sponging dolphin with a fish in her mouth, while blurry, suggests that they too could be after grubfish.