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Brainy lizards rival birds in intelligence

Reptiles have long been thought to be dim-witted, but a new study in Biology Letters finds that the Puerto Rican anole, a type of lizard, can match birds in smarts. Using cognitive tests that have been previously used on birds, researchers with Duke University found that the lizards were capable of solving a problem they’ve never encountered before, remembering the solution in future trials, and even changing techniques when presented with new challenges. In fact, the tiny anoles solved the test with fewer tries than birds. Given reptiles’ reputation of being slow-on-the uptake the head author, Manuel Leal, said the findings are ‘completely unexpected’.

Puerto Rican anoles, Anolis evermanni, were tested on a food-finding apparatus normally used on birds. The lizards showed they could solve a novel problem, remember solutions and “unlearn” incorrect approaches. Credit: Manuel Leal, Duke University

For the test the Puerto Rican anoles (Anolis evermanni) were provided with two wells, one held a tasty worm but was covered by a cap, while the other was empty. To reach the reward–the worm–the anoles had to bump or bite the cap out of the way. On average the lizards solved the problem with three fewer tries than birds.

“They’d put their snout under the little plastic chip and then quickly bump it,” Leal said in a press release. “They don’t do this in the wild.”

The lizards were only given one chance per day, while birds were given several every day. If the lizard didn’t succeed they had to wait 24 hours for the next opportunity to feed.

Next researchers put two caps–one bright and one dull–over the wells, and the lizards quickly learned to associate the bright cap with the worm, ignoring the dull one. After this, the researchers tried to trick the lizards: they switched the worm, hiding it under the dull cap. This proved more difficult. But after a few trials, two of the four lizards began to flip the dull cap instead of the bright one.

“We named these two Plato and Socrates,” Leal says.

A related species of anole, but not used in the research.

While the study found unexpected cognitive abilities in the lizards, an expert on bird intelligence, Louis Lefebvre with McGill University, says that the study doesn’t necessarily mean lizards are smarter than birds since birds still have larger body-to-brain ratios than reptiles. Instead it may mean that anoles are among the most intelligent of the reptiles.

“We know birds and mammals have bigger brains and that within bird species and within mammal species, the bigger the brain is, the higher the chance of that larger-brained species making it when moving to a new environment,” Lefebvre said in a press release. “It may be the same with lizards.”

Anoles have been shown to be especially successful at surviving in new habitats. There are over 400 species of anoles, making them the largest genus in the reptile class.

For his part, Leal plans to test other lizards and compare body-to-brain size this year.

For decades researchers have discovered that the world’s animals are often far more clever than society has given them credit for. Along with the great apes, crows and octopus have been shown to use tools. Bees can count. Hens experience empathy for their chicks. Paper wasps can other recognize wasp-faces. The more we learn about animal intelligence, the less distinct we are.

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