03/08/2011 07:32 pm ET | Updated May 25, 2011

Elephants Trump Magic Goldfish

A few weeks ago, millions of Chinese television viewers watched in disbelief how a magician's goldfish swam in tight formation. Goldfish are not known for compact schools, but here they moved like fighter planes in perfect synchrony seemingly guided by the magician's hands. The trick was done in a shallow tank on a table, which is why the Internet was soon abuzz with speculation that the fish had been fed iron while someone was moving magnets under the table. Animal rights activists were outraged. The magician never denied this theory, but claimed his fish were happy and healthy.

It is hard to get animals which normally pay little attention to each other to do things together. One can teach dolphins to jump simultaneously out of the water precisely because they show similar behavior spontaneously, but try to make two domestic cats jump together and you will fail. Cats are solitary hunters, and have no talent for synchronization.

Elephants, in contrast, are known to travel together and help each other, such as when one of them is injured or a baby has slid into a mud hole. This is why we set up an experiment to see how well these animals understand cooperation. We used a task developed ages ago for chimpanzees. Two apes are facing a sliding tray that they can pull towards themselves, but that is too heavy for one ape on his own. This means that the apes have to work together to obtain the food placed on the tray. Chimpanzees turn out to be excellent at this task.

To test if elephants can do the same is easier said than done, even with "tame" elephants controlled by mahouts. First of all, elephants are dangerous and kill many mahouts and tourists every year. Joshua Plotnik was brave enough to set up the experiment in Thailand. Of course, the mahouts were not allowed to sit on their animals during the test, but were kept at a distance. The second problem is that it is impossible to design an apparatus too heavy for two elephants to pull. We were not ready to build something as big as an 18 wheeler truck!

The solution was to guide a single rope entirely around the tray: pulling at only one end of the rope would just unthread it. The elephant would end up empty-trunked, with just a piece of rope. Only if both ends of the rope were pulled simultaneously by two elephants would the tray move with it, and could they reach the buckets with corn attached to the tray. They were thus forced to act together.

Drawing of the experimental set-up with a view from above and from the side.

This ingenious design allowed us to test how well elephants understood each other's role. After having released one elephant towards the apparatus first, he would need to wait for the other. If he was impatient and pulled on his own, the test would be over without rewards. From a tree above the elephants, Josh videotaped all of the action. It turned out that elephants patiently wait for up to 45 sec for a helping partner, and that they refuse to pull if the partner's rope is out of reach. They know not only that another elephant is needed, but also that he has to be able to pull. Elephants seem in fact as good at this task as chimpanzees.

And all this without any need to feed them iron.