It’s easy to assume that tortoises are just lumbering living rocks, too slow to learn party tricks and certainly not smart enough to recall long-term memories. But a new study suggests we might be greatly underestimating these shelled amigos.
A new study, published in the journal Animal Cognition, has shown how giant tortoises can be taught new tasks and even perform them almost a decade later after being trained – which is good news, considering they can live for over a century.
Almost a decade ago, scientists from Okinawa Institute of Science and Technology set out to test the brainpower of the Galápagos giant tortoises and Seychelles, or Aldabra, giant tortoises housed at Tiergarten Schönbrunn, a zoo in the Austrian capital, Vienna.
"We knew from the zoo workers that the turtles clearly recognize the keepers that work with them. There was a report of target training Aldabras for veterinary handling. When we went into older literature of sea voyages we found accounts that in the same text called them unintelligent and then described how easily they were trained using negative reinforcement," lead author Michael Kuba explained to IFLScience. (In case you're wondering, "turtle" is used to describe both turtles and tortoises in American English).
Using a form of conditioning called positive reinforcement training, The tortoises were trained to associate a reward (ie food) with a specifically colored ball on a stick. When presented with two different colored balls, they were able to select the ball associated with food, bite it, and receive the reward.
They then assessed whether the tortoises had remembered their training after 95 days. All of the animals approached and responded to the sticks, just as they were trained to months ago, although they were unable to immediately recall the specific color of the ball. Even more remarkably, the same group of tortoises was tested 9 years later and found to still possess the memories of their training.
There are thought to be 15 known species of giant tortoise, though every so often they seem to pop up again after being long-thought extinct. The Galápagos giant tortoise complex includes some of the largest living species of tortoise. Known to weigh up to 500 pounds (227 kilograms), they are also one of the longest-living invertebrates, easily reaching the age of 100 years old in the wild. Seychelles giant tortoises can also live to grand old ages. The oldest known living specimen, an individual named Jonathan, is thought to be around 187 years old, which also makes him the oldest animal in the world.
Scientists often subject mammals, birds, and even fish to intelligence tests, although reptiles – not considered the sharpest species in the animal kingdom – have been largely ignored from this debate. However, this new study sheds some light on the misunderstood cognitive abilities of our cold-blooded counterparts.
"We hope this work challenges the assumptions about reptile intelligence," added Kuba. "Work on cognition in reptiles is often limited by availability. The more species we test the clearer the picture becomes that many reptiles have similar cognitive capacity to mammals."