Smarter than the average reptile?

By AAP with AG Staff 9 August 2011
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Anolis lizards have been shown to have “higher intelligence” by swiftly adapting behaviour to changing circumstances.

SURPRISE RESULTS FROM a group of US biologists show tropical lizards share the same level of intelligence as birds and mammals. The results were “totally unexpected”, says Professor Manuel Leal, the study’s main author at Duke University in North Carolina, USA.

According to conventional scientific thinking, lizards have limited cognitive ability compared to birds and mammals. But the tropical Anolis lizard is able to solve problems and even adapt learned abilities to changed circumstances, according to the report’s findings, which have been published in the journal Biology Letters.

“Evolution can endow a lizard or a frog with substantial brainpower – whether or not this happens depends on how useful that behavioural flexibility is in the animal’s day-to-day life,” comments Professor Rick Shine an expert on reptiles at the University of Sydney. “It seems like these little tropical tree-dwelling lizards encounter enough complicated problems in finding prey, that they have evolved an ability to think through the kind of hurdles presented to them in this study.”

Worm in a hole

Scientists at Duke University studied six Anolis evermanni lizards by setting them the task of locating a worm in one of two holes. The hole containing the worm was covered with a lid. Four of the six lizards successfully completed the test by either lifting the lid with their mouths or by biting into the covering and then removing it. “This is a completely new form of preying behaviour,” writes Manuel and graduate student Brian Powell, the study’s co-author.

The lizards were also able to use the newly acquired strategy of opening the lid in other circumstances. When both holes were covered with different types of lids, the lizards correctly identified the hole with the worm, proving they had learned to identify the colour of the lid that covered the worm.

Two of the lizards were even able to amend their newly attained knowledge. When Manuel and Brian placed the worm in the hole that until then had always been empty, all of the lizards at first tried the wrong hole.

Higher arithmetic

However, two lizards recognised the changed circumstances and found the worm in the new location. “The ability to adapt behaviour is an indicating sign of an animal with higher intelligence,” says Harvard University biologist Professor Jonathan Losos, who was not involved in the study.

Until now lizards were not listed among those creatures. The study’s authors believe that the learning aptitude of the Anolis group of lizards has contributed to its widespread proliferation in the tropics.

“Studies like this show us just how little we really know about the other species that we share the world with – and how we uncritically assume that the only smart animals will be those that look like human beings,” Rick Shine told Australian Geographic. “I doubt that the little lizards that live in my Sydney backyard entertain themselves by solving higher arithmetic puzzles as they bask in the sun, but they are probably a lot smarter than we think.”