- Reptile intelligence has long been considered inferior to that of birds and mammals. But recent studies in reptile cognition show reptiles have a profound understanding of their environment.
- Reptiles’ understanding of their surroundings and their evolution of learning can play a part in biodiversity conservation and ecosystem service provisioning, especially on agricultural lands.
- This post is a commentary. The views expressed are those of the author, not necessarily Mongabay.
“Deep inside the skull of every one of us there is something like a brain of a crocodile” – Carl Sagan, Cosmos.
In science, reptiles have been considered to be of lower intelligence compared to birds and mammals. Dimwitted, even. But over the last decade, significant research has been out in reptile cognition, and the results have been truly exhilarating.
Mammals and birds are generally considered the intelligent class of animals. However, the basic brain structure in both these classes is similar to that of the reptilian brain, which diversified 280 million years ago. Reptiles and mammals are the only vertebrates to have a cerebral cortex with a clear, though simple, three-layered structure, similar to that of the mammalian allocortex. The reptilian ventral pallium gives rise to the dorsal ventricular ridge, which contributes to the complex cognitive abilities of birds. Although the reptilian cortex contains fewer subdivisions than mammals, the fundamental parts remain the same. It is subdivided into a medial cortex, better known as the hippocampus; a lateral cortex, equivalent to the mammalian piriform cortex; and a dorsal cortex which receives multimodal inputs (like the visual inputs in turtles).
Perhaps there is no reason to not acknowledge the cognitive abilities in reptiles, as, since they evolved, there has been enough time for further evolution of the cognitive mechanisms. Besides, the basic brain structure of reptiles should also share behavioral and morphological similarities with mammals and birds.
Charles Darwin, in his second book “The Descent of Man and Selection in Relation to Sex,” mentions that other animals differ cognitively from humans only in degree but not in kind. In the reptilian brain, being of primitive, ancestral form, the structural and functional complexity may not be as sophisticated as those of birds or mammals. Hence the cognitive processes are fairly simple compared to the higher taxa.
Reptiles consist of three major orders — Chelonia, Crocodilia and Squamata — and all of them have a profound understanding of their environment. Over decades, scientists have been working towards understanding how they do what they do, and the results have often been surprising. Reptiles have excelled in learning about space and their surroundings, as well as about color and taste. Researchers have also observed social learning, eavesdropping on the warning sounds from other species, reversal learning, solving novel tasks and evidence of good memory.
Why should we care about reptile intelligence?
Although the information on reptile cognition is plentiful, we have, so far, not really considered reptile cognition as having any practical implications in solving real-life challenges. One such implication can be seen in conservation. For example, goannas and blue-tongued skinks in Australia face fatal risks upon consuming cane toads for their intolerance towards the Bufonidae toxin secreted by the toads. Training goannas and blue-tongued skinks with cane toad sausages laced with nausea-inducing chemicals caused aversion learning. When released in the wild, trained reptiles learned to avoid the cane toads. This learning and memory improved their survival rate.
Another possible implication is in preserving their ecological functioning. Most probably stemming from our ignorance, we have yet to considered the ecosystem functions they deliver. For example, reptiles form a herald part of the agricultural community of biodiversity and are, to some extent, resistant to pesticides. Additionally, many of these farm-inhabiting reptiles are also insectivores which makes them relevant choices as bioregulators.
With our ever-increasing population, it is practically impossible to either prevent increased land claims by agriculture or to curb the amount of agricultural produce – agricultural land use can only increase in the coming years. What will be left of the biodiversity is what is bothering. However, the consequences are more than losing just a few counts of species. One of the major challenges with increasing crop production is the increase in loss in crop yield due to pest attacks. Several mitigating measures have been solicited over the past few decades ranging from chemical to cultural practices. With the detrimental impacts of pesticide on the ecosystem, crop health, human health, and biodiversity, the only option left is to use natural resources like natural enemies in regulating crop pests. The question here is, ‘can cognition biology help in advancing pest management science?’
A quick overview of reptiles’ cognitive abilities shows that they can discriminate between color, odor, shape and quantity. They can remember, decide and even follow social cues. For example, tortoises distinguish between yellow color over blue or white, a learning evolved for selecting carotenoid-rich food. Color discrimination in fruits and flowers has been widely studied in herbivorous reptiles like iguanas, tortoises, and turtles. Learning ability in reptiles can thus offer an opportunity to improve their ecosystem service provisioning.
Likewise, learning and remembering about refuge, which is “spatial cognition,” can also benefit bioregulation. Reptiles can remember rewarding foraging patches. Further, being able to pick on social cues, lizards have been seen to observe bird movement to opportunistically locate fig trees which are a rich source of insects. Tortoises can follow social cues to learn their way around a barrier to obtain food. Reptiles exhibiting such behavioral flexibility allow us to examine such abilities through the lens of bioregulation. However, more refined experiments are needed, which are not only relevant for pest regulation but also relevant to the animal itself in the wild.
Our understanding of the cognitive abilities of reptiles is still incomplete and requires more research. Our idea of these animals being “sedentary, impassive creatures operating as instinctive machines” needs to be rapidly replaced for a fuller realization of the functional roles they play in sustaining our ecosystem. It is time we realize the importance of having these animals around us for their services to the ecosystem many of which remain unnoticed by us.
Banner image: A chameleon on a branch. Image by Hasmik Ghazaryan Olson via Unsplash (Public domain).
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Darwin, C. (1871). The descent of man. New York: D. Appleton. doi:10.1037/12293-000
Kis, A., Huber, L., & Wilkinson, A. (2015). Social learning by imitation in a reptile (Pogona vitticeps). Animal cognition, 18(1), 325-331. doi:10.1007/s10071-014-0803-7
Leal, M., & Powell, B. J. (2012). Behavioural flexibility and problem-solving in a tropical lizard. Biology letters, 8(1), 28-30. doi:10.1098/rsbl.2011.0480
Burghardt, G. M. (2013). Environmental enrichment and cognitive complexity in reptiles and amphibians: Concepts, review, and implications for captive populations. Applied Animal Behaviour Science, 147(3-4), 286-298. doi:10.1016/j.applanim.2013.04.013
Price‐Rees, S. J., Webb, J. K., & Shine, R. (2013). Reducing the impact of a toxic invader by inducing taste aversion in an imperilled native reptile predator. Animal Conservation, 16(4), 386-394. doi:10.1111/acv.12004
Pellitteri-Rosa, D. A. N. I. E. L. E., Sacchi, R. O. B. E. R. T. O., Galeotti, P. A. O. L. O., Marchesi, M., & Fasola, M. A. U. R. O. (2010). Do Hermann’s tortoises (Testudo hermanni) discriminate colours? An experiment with natural and artificial stimuli. Italian Journal of Zoology, 77(4), 481-491. doi:10.1080/11250000903464067
Blázquez, M. C., & Rodríguez‐Estrella, R. (2007). Microhabitat selection in diet and trophic ecology of a spiny‐tailed iguana Ctenosaura hemilopha. Biotropica, 39(4), 496-501. doi:10.1111/j.1744-7429.2007.00294.x
Ventura, D. F., Zana, Y., Souza, J. D., & Devoe, R. D. (2001). Ultraviolet colour opponency in the turtle retina. Journal of Experimental Biology, 204(14), 2527-2534. doi:10.1242/jeb.204.14.2527
Whiting, M. J., & Greeff, J. M. (1999). Use of heterospecific cues by the lizard Platysaurus broadleyi for food location. Behavioral Ecology and Sociobiology, 45(6), 420-423. doi:10.1007/s002650050579
Wilkinson, A., Kuenstner, K., Mueller, J., & Huber, L. (2010). Social learning in a non-social reptile (Geochelone carbonaria). Biology letters, 6(5), 614-616. doi:10.1098/rsbl.2010.0092
Gaalema, D. E. (2011). Visual discrimination and reversal learning in rough-necked monitor lizards (Varanus rudicollis). Journal of Comparative Psychology, 125(2), 246–249. doi:10.1037/a0023148