Beasts of science: the funny memory of giant tortoises

Do you know Diego’s story? Diego is a giant turtle. A giant Galapagos tortoise, to be exact. A male, as his name suggests. He was baptized at the San Diego Zoo (USA). And what is special about it is that it only tells itself, he saved his species — the Espanola tortoise — from extinction. Thanks to a libido a little crazy !

When scientists turn to him, in the late 1970s, Diego is already just under a hundred years old. But never mind, because the giant tortoises, whether they come from the Seychelles – an archipelago in the Indian Ocean attached to Africa – or the Galapagos – an archipelago in the Pacific Ocean – are true champions of longevity. In captivity, several of them are over 150 years old.

In a zoo in Calcutta (India), a certain Adwaita would have even reached the canonical age of 255 years! Now another giant tortoise from the Seychelles is considered the oldest living animal in the world. Jonathan would be around 190 years old. And he lives a golden retirement in the gardens of the residence of the governor of Saint Helena.

But, back to Diego. In 1976, his species was in great danger. Only fourteen individuals remained. Fortunately, Diego arrived. Without rushing. In some 40 years, he made no less than… 900 babies! Contributing thus largely to bring back the tortoises of Espanola on the way of serenity. The species now has about 2,000 members again.

Despite this kind of crazy stories, it must be recognized that, at first glance, turtles do not seem the most interesting. They have a reputation for moving slowly — although surely — at an average of 250 meters per hour for tortoises. L’amalgam is often made between this slowness of movement and… a supposed slowness of mind. A received idea that sticks to the skin of turtles since their discovery. As they simply let themselves be picked up and placed on the back by whalers or pirates who saw in them reserves of fresh meat because the giant tortoise can thus survive for a good while, without even drinking or eating, but it is unable to escape.

However, researchers see giant tortoises as much more intelligent animals than they seem. Darwin, already, had noted that the giant tortoises of the Galapagos have the habit of traveling long distances to find food or drink, to sleep or to bathe. What to imagine them a good memory. If only to find their way back.

A memory reinforced by social interactions

It took a while for scientists to confirm this with the collaboration of turtles held captive in zoos. The researchers first managed to teach these turtles to bite a colored ball attached to the end of a stick. The key is a reward in the form of a treat. And learning this type of simple task was already a first intelligence sign.

But the researchers wanted to see if they could go further. They taught the turtles to move towards the bite ball when it was one or two meters away. Finally, the last step, the most complex: they trained the turtles to each bite a ball of color different. The giant tortoises rose to the challenge.

Three months later, okay, the turtles had forgotten the color of the ball they had been assigned. But they still remembered what scientists expected of them. Bite into bullets. Three months later ? This is already a good proof of the memory of turtles. However, the best part happened when scientists repeated the test… nine years later. The turtles had not forgotten.

The other surprise of the experiment was that the turtles who were taught in groups showed themselves able to learn faster than the others. An amazing proof of social interaction for animals that are not known to be particularly social. Enough to show that we still have a lot to learn from the cognitive capacities of reptiles. And that, even if these results have yet to be confirmed on a larger number of individuals, giant tortoises, despite their good-natured appearance, seem not to be so stupid!