Scientists Show That Tortoises Have Excellent Long-term Memories

A team of researchers has just showed that reptiles may have better long-term memories than previously believed. Red-footed tortoises were trained to recognize specific visual cues associated with food and still remembered the cues when retested 18 months later. The details are in a paper that was just published in the journal Biology Letters.

Long-term memory can mean the difference between survival and death when food is scarce. Animals that can remember the locations of consistent food sources don’t have to exert as much energy looking for food. Although researchers have showed that reptiles can remember specific locations and cues, scientists were unsure how long they could retain this type of information. Some reptile species, such as the red-footed tortoise (Chelonoidis carbonaria), can live for decades. This long lifespan prompted scientists to test if red-footed tortoises could remember food locations after a significant amount of time had passed.

Researchers from the University of Lincoln in the United Kingdom trained captive red-footed tortoises to associate specific food types and quantities with different colored sheets. The tortoises quickly learned which colors signified the location of their favorite mango-flavored food (as opposed to a less-preferred apple jelly). They also learned to associate colored sheets with different food quantities and chose to walk towards the color of a sheet that would contain large amounts of food. When the research team tested the tortoises 18 months later, the reptiles remembered all of the cues—preferring colored sheets that would contain large amounts of their preferred food item.

The study demonstrates that red-footed tortoises have excellent long-term memories for finding food sources and can remember visual cues associated with food for over a year. The team points out that the tortoises would naturally be found in forest habitats, which tend to have resources spread between patches of land. A long-term memory would help the reptiles avoid wasting energy as they search the forest for food. Although red-footed tortoises were the only reptile species tested, it’s possible that other long-lived reptiles have similar memory abilities.

REFERENCE

Soldati et al. Long-term memory of relative reward values. Biology Letters (2017).

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