Research has revealed that lizards are surprisingly adept at solving novel problems, and in some tests, perform better than other animal species that are thought to be more cognitively advanced.1 The study was done at Duke University by biologists Manuel S. Leal and Brian J. Powell. After seeing an experiment in which sparrows flipped caps to access food, Leal set out to determine how lizards would fare at the same task, testing long-ignored reptile problem-solving abilities.2
Leal and Powell chose Puerto Rican Anoles (Anolis evermanni) as their research subjects. Like most lizards, this species catches its prey by attacking from above. But when it’s not possible to use this usual attack method, the anoles proved that they could find other ways to get to their prey. The anoles were presented with wooden blocks that had two compartments, each topped with a differently colored lid. One compartment contained an insect (with a blue lid), the other was empty (with a blue and yellow lid). The majority of the lizards removed the lids so that they could eat the insect, either by biting the lid and dragging it off, or levering the lids off with their noses.
“They’d put their snout under the little plastic chip and then quickly bump it,” Leal said. “They don’t do this in the wild.”
Compared to the sparrows, the anoles actually did better. This is particularly impressive because unlike the birds, the anoles only ate once per day, and thus had only one chance to solve the problem successfully. They would have to rely on their memories in order to properly solve the problem the next day. The sparrows had 6 chances per day, and still did not outdo the anoles.
It was thought that the anoles were associating the blue lids with their prey, and thus correctly chose which compartment held the insects most of the time. To test this, the insects were placed under the other multicolored lids. Indeed, the anoles were first drawn to the blue lids. However, once they discovered that there was no insect in the compartment, a few of them quickly directed their attention toward the other lids.
The results of these experiments show that the anoles are not only very flexible in problem-solving, but are also fast learners. Another study3 involving black-throated monitor lizards had similar findings: when faced with plastic tubes containing prey, the lizards figured out how to undo the tubes’ hinged doors to get at the food within 10 minutes. The lizards got faster at opening the tubes in every subsequent test. Given how well lizards of two very different species have performed in problem-solving tasks, it is worth reevaluating our estimations of their intelligence and mental capabilities. To learn more about the research on anoles, see the abstract and video below.
The role of behavioural flexibility in responding to new or changing environmental challenges is a central theme in cognitive ecology. Studies of behavioural flexibility have focused mostly on mammals and birds because theory predicts that behavioural flexibility is favoured in species or clades that exploit a diversity of habitats or food sources and/or have complex social structure, attributes not associated with ectothermic vertebrates. Here, we present the results of a series of experiments designed to test cognitive abilities across multiple cognitive modules in a tropical arboreal lizard: Anolis evermanni. This lizard shows behavioural flexibility across multiple cognitive tasks, including solving a novel motor task using multiple strategies and reversal learning, as well as rapid associative learning. This flexibility was unexpected because lizards are commonly believed to have limited cognitive abilities and highly stereotyped behaviour. Our findings indicate that the cognitive abilities of A. evermanni are comparable with those of some endothermic species that are recognized to be highly flexible, and strongly suggest a re-thinking of our understanding of the cognitive abilities of ectothermic tetrapods and of the factors favouring the evolution of behavioural flexibility.
This article was written by Amanda Pachniewska, founder & editor of Animal Cognition.
1 – Manuel S. Leal, Brian J. Powell
Behavioral Flexibility and Problem-Solving in a Tropical Lizard
2 – Brainy Lizards Pass Test For Birds
3 – Jennifer D. Manrod, et al.
Rapid Solving of a Problem Apparatus by Juvenile Black-Throated Monitor Lizards (Varanus albigularis albigularis)