Ben Creisler
Some recent papers about reptile intelligence...
Posted earlier on the DML in preprint form, now in final form with a free pdf:
E. Font, R. GarcÃa-Roa, D. Pincheira-Donoso & P. Carazo (2019)
Rethinking the Effects of Body Size on the Study of Brain Size Evolution.
Brain, Behavior, and Evolution 93: 182â195
doi:
https://doi.org/10.1159/000501161https://www.karger.com/Article/FullText/501161Free pdf:
https://www.karger.com/Article/Pdf/501161Body size correlates with most structural and functional components of an organismâs phenotype -- brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.
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Tamar Gutnick, Anton Weissenbacher & Michael J. Kuba (2019)
The underestimated giants: operant conditioning, visual discrimination and long-term memory in giant tortoises.
Animal Cognition (advance online publication)
doi: 10.1007/s10071-019-01326-6
https://link.springer.com/article/10.1007%2Fs10071-019-01326-6Relatively little is known about cognition in turtles, and most studies have focused on aquatic animals. Almost nothing is known about the giant land tortoises. These are visual animals that travel large distances in the wild, interact with each other and with their environment, and live extremely long lives. Here, we show that Galapagos and Seychelle tortoises, housed in a zoo environment, readily underwent operant conditioning and we provide evidence that they learned faster when trained in the presence of a group rather than individually. The animals readily learned to distinguish colors in a two-choice discrimination task. However, since each animal was assigned its own individual colour for this task, the presence of the group had no obvious effect on the speed of learning. When tested 95 days after the initial training, all animals remembered the operant task. When tested in the discrimination task, most animals relearned the task up to three times faster than naÃve animals. Remarkably, animals that were tested 9 years after the initial training still retained the operant conditioning. As animals remembered the operant task, but needed to relearn the discrimination task constitutes the first evidence for a differentiation between implicit and explicit memory in tortoises. Our study is a first step towards a wider appreciation of the cognitive abilities of these unique animals.
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Tool use has been documented across a diverse array of animals; however, this behavior has received little attention in reptiles. Recently, researchers reported observations of two crocodilian species apparently using sticks as lures to aid in the capture of nesting birds, but the evidence for the behavior was anecdotal and correlative. To explore the behavior in a more controlled situation we designed an experiment to explicitly test the ability of crocodilians to tailor stick-displaying behaviors to specific environmental contexts using four captive pond-dwelling American alligator (Alligator mississippiensis) populations, two of which reside near bird rookeries and two of which do not. During bird nesting season we added sticks to each pond and observed the frequency with which each population exhibited stick-displaying behaviors. We found that in most comparisons the frequency of stick-displaying behavior did not differ between rookery and no-rookery sites, while in one comparison the alligators at a no-rookery site actually displayed the behavior more frequently than a paired rookery site. Our results do not generally support the hypothesis that crocodilians tailor stick-displaying behaviors to specific environmental contexts, therefore the hypothesis that crocodilians are true tool users is also called into question. Furthermore, our results suggest that experiments on captive populations are not the ideal way to study stick-displaying behavior because of issues like unrealistic alligator densities and food provisioning.