Turtle Power: Study Finds Giant Tortoises Have Strong Memories, High Intelligence

OKINAWA, Japan — Move over elephants, giant land tortoises may just be the kings of the animal kingdom when it comes to memory. Historically, these large reptiles haven’t been considered especially intelligent, but a new study conducted at the Okinawa Institute of Science and Technology is suggesting both their overall brain power and memory skills have been greatly underestimated.

“When first discovered, giant land tortoises were viewed as stupid because explorers could simply collect and store them on ships as a supply of fresh meat,” explains study author and postdoctoral scholar Dr. Tamar Gutnick in a statement.

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A friendship of a decade: Dr. Tamar Gutnick pets her favorite tortoise, George, a 100-year-old Aldabra tortoise housed in Vienna Zoo. (Photo credit: OIST)

Despite this unfair stereotype, the research team say there have been signs of these turtles’ high intelligence and superior memory for a long time. In fact, Charles Darwin himself noted that Galapagos tortoises tended to travel great distances between the locations they typically ate, slept, and bathed, which would require sufficient memory skills in order to remember their routes back and forth. Additionally, other explorers around this time period had noted that tortoises were capable of being trained to stay in one location aboard ships.

“We also observed firsthand that tortoises recognized their keepers, so we knew they were capable of learning,” Dr. Gutnick adds. “This research shows the rest of the world just how smart they are.”

This new set of research, according to Dr. Gutnik, is the culmination of nearly a decade’s worth of time spent observing and spending time with these unique and fascinating creatures.

“When I met the tortoises, I immediately fell in love with them,” she comments. “It was clear to me that they all had very distinct – and often cheeky – personalities.”

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So, in an effort to gauge their intelligence, Dr. Gutnik and her colleague, Dr. Michael Kuba, trained a group of six tortoises to perform a series of three different tasks, each one more challenging than the last. A conditioning method called positive reinforcement training, in which the turtles were rewarded with food for correctly completing a task, was used to help incentivize the reptiles.

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Purple or green? Jumbo, a Galapagos tortoise from Zürich Zoo successfully bites the correctly colored target. (Photo credit: OIST)

The first task was fairly simple, the tortoises were taught to bite a colored ball positioned on the end of a stick. Once each turtle had mastered that, the research team upped the ante for the second task; this time the tortoises had to walk forward a bit in order to reach and bite the colored ball, which was placed about three to six feet away from them. For the final and third task, each tortoise was assigned a specific color and trained to only bite balls featuring the same color when presented with two options.

Then, the researchers waited three months before testing the same tortoises on the three tasks. Incredibly, all of the tortoises immediately remembered and correctly performed the first two tasks. The third task proved to be a bit harder, as the turtles were not able to remember the colors they had been assigned a few months prior. However, five out of the six tortoises were able to re-learn which colored ball to bite much faster than it originally took them, indicating the presence of residual memory.

The researchers also re-visited three different tortoises they had trained in similar tasks nine years ago, and amazingly, all three remembered a significant portion of the behaviors they had been taught nearly a decade ago.

Finally, the research revealed another interesting finding: tortoises taught in groups tend to learn more efficiently than those taught separately. This indicates that tortoises likely depend on each other quite frequently in the wild to learn about their surroundings and find sources of food or water.

“This was a very unexpected result,” Dr. Gutnick says. “Giant land tortoises are not known for being particularly social animals but the increase in learning speed was unmistakable.”

The study is published in the scientific journal Animal Cognition.

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