They’re not as slow as we thought.

Turtles and tortoises have been around since the middle Jurassic, making them one of the oldest groups of reptiles still in existence. However, while biologists have studied these creatures for centuries, surprisingly little is known about their cognitive abilities. When it comes to giant land tortoises, almost nothing is known about their cognitive power.

We do know that they are visual animals. They travel long distances in the wild, interacting with other individuals, but giant tortoises have been described as “living rocks” — not just due to their slow movement, but also due to their presumed inflexible cognitive abilities. Darwin observed that they travel long distances for purposes that are not always apparent, and a 1914 study noted that “The tortoises do a great deal of apparently unnecessary traveling; and, though slow, are so persistent in their journeys that they cover several miles a day.”

But while the tortoises might be slow to move, they are not slow to forget.

Tamar Gutnick and Michael Kuba at the Hebrew University in Jerusalem, Israel, and Anton Weissenbacher at Schönbrunn Zoo in Vienna trained Galapagos tortoises (Chelonoides nigra) and Aldabra tortoises (Aldabrachelys gigantea) to bite a ball of a particular color: blue, green or yellow. They were presented with a colored dog toy attached to the end of a dowel. When they would bite the right color, they would get a treat. All the animals easily learned this task.

After a while, tortoises would only bite one color.

Then, the researchers came back 95 days after the initial training to see if the tortoises still remember the color — and they did. All 6 animals who received the training remembered the task successfully.

Remarkably, even when researchers returned after 9 years, the 3 available tortoises all remembered the “right” color to eat.

It’s too small of a sample size to draw any statistics, but the fact that the tortoises from both species seemed to remember the task even after such a long time is a strong indication that we may have underestimated their abilities.

“Our results highlight flexibility in learning in tortoises and support growing evidence of the significance of social interaction and social learning in reptiles. Comparative study of a variety of reptile species, likely including zoo-based research, will allow for a more thorough understanding of the ecology and evolution of learning in reptiles and processes shaping social learning in all vertebrates,” the study concludes.

The study has been published in the journal Animal Cognition.