Spatial learning in captive and wild-born lizards: heritability and environmental effects

Heritability of cognitive performance in wild Western Australian magpies

Individual differences in cognitive performance can have genetic, social and environmental components. Most research on the heritability of cognitive traits comes from humans or captive non-human animals, while less attention has been given to wild populations. Western Australian magpies (Gymnorhina tibicen dorsalis, hereafter magpies) show phenotypic variation in cognitive performance, which affects reproductive success. Despite high levels of individual repeatability, we do not know whether cognitive performance is heritable in this species. Here, we quantify the broad-sense heritability of associative learning ability in a wild population of Western Australian magpies. Specifically, we explore whether offspring associative learning performance is predicted by maternal associative learning performance or by the social environment (group size) when tested at three time points during the first year of life. We found little evidence that offspring associative learning performance is heritable, with an estimated broad-sense heritability of just -0.046 ± 0.084 (confidence interval: -0.234/0.140). However, complementing previous findings, we find that at 300 days post-fledging, individuals raised in larger groups passed the test in fewer trials compared with individuals from small groups. Our results highlight the pivotal influence of the social environment on cognitive development.

Navigational experience affect cognition: Spatial learning capabilities in captive and wild-born tuco-tucos

There is a growing recognition of the influence of both genetic and ecological context in shaping different cognitive traits. The hippocampal region is identified as a critical area for memory and learning in mammals, susceptible to modification by environmental influences. Although previous studies have identified the effects of various factors on cognitive parameters during early development, comparatively few research was conducted on wild species to analyze the role of natural environmental stimuli in the formation of spatial learning and memory abilities. Thus, to assess the importance of exposure to a complex and challenging environment during early development, we compared spatial learning performance of captive-born tuco-tucos with previous data obtained in our laboratory from wild-born adult tuco-tucos. The results showed that wild-born individuals learned faster, requiring less time to complete a labyrinth and making fewer errors than those who had no experience in their natural environment. These findings underscore the importance of considering ecological factors in understanding the evolution of brains and cognitive abilities.

Effects of acute maternal stress induced by predator cues on spatial learning and memory of offspring in the subterranean rodent Ctenomys talarum

One of the main selection pressures to which animals are exposed in nature is predation, which affects a wide variety of biological traits. When the mother experiences this stressor during pregnancy and/or lactation, behavioral and physiological responses may be triggered in the offspring as well. Thus, in order to broaden and deepen knowledge on the transgenerational effects of predation stress, we evaluated how maternal stress experienced during pregnancy and/or lactation affects the spatial abilities of progeny at the onset of adulthood in the subterranean rodent Ctenomys talarum. The results showed that, contrary to what was observed in other rodent species, maternal exposure to predator cues during pregnancy and lactation did not negatively affect the spatial abilities of the offspring, even registering some minor positive effects. Concomitantly, no effects of predatory cues on physiological parameters associated with stress were observed in the progeny. This difference in results between the present study and previous works on maternal stress highlights the importance of considering the species to be evaluated (strain, age and origin-wild or captive-) and the type of stressor used (artificial or natural, intensity of exposure) in the evaluation of the possible transgenerational effects of maternal stress.

Artificial selection for reversal learning reveals limited repeatability and no heritability of cognitive flexibility in great tits (Parus major)

Cognitive flexibility controls how animals respond to changing environmental conditions. Individuals within species vary considerably in cognitive flexibility but the micro-evolutionary potential in animal populations remains enigmatic. One prerequisite for cognitive flexibility to be able to evolve is consistent and heritable among-individual variation. Here we determine the repeatability and heritability of cognitive flexibility among great tits (Parus major) by performing an artificial selection experiment on reversal learning performance using a spatial learning paradigm over three generations. We found low, yet significant, repeatability (R = 0.15) of reversal learning performance. Our artificial selection experiment showed no evidence for narrow-sense heritability of associative or reversal learning, while we confirmed the heritability of exploratory behaviour. We observed a phenotypic, but no genetic, correlation between associative and reversal learning, showing the importance of prior information on reversal learning. We found no correlation between cognitive and personality traits. Our findings emphasize that cognitive flexibility is a multi-faceted trait that is affected by memory and prior experience, making it challenging to retrieve reliable values of temporal consistency and assess the contribution of additive genetic variation. Future studies need to identify what cognitive components underlie variation in reversal learning and study their between-individual and additive genetic components.

Learning with lacertids: Studying the link between ecology and cognition within a comparative framework

Cognition is an essential tool for animals to deal with environmental challenges. Nonetheless, the ecological forces driving the evolution of cognition throughout the animal kingdom remain enigmatic. Large-scale comparative studies on multiple species and cognitive traits have been advanced as the best way to facilitate our understanding of cognitive evolution, but such studies are rare. Here, we tested 13 species of lacertid lizards (Reptilia: Lacertidae) using a battery of cognitive tests measuring inhibitory control, problem-solving, and spatial and reversal learning. Next, we tested the relationship between species' performance and (a) resource availability (temperature and precipitation), habitat complexity (Normalized Difference Vegetation Index), and habitat variability (seasonality) in their natural habitat and (b) their life history (size at hatching and maturity, clutch size, and frequency). Although species differed markedly in their cognitive abilities, such variation was mostly unrelated to their ecology and life history. Yet, species living in more variable environments exhibited lower behavioral flexibility, likely due to energetic constrains in such habitats. Our standardized protocols provide opportunities for collaborative research, allowing increased sample sizes and replication, essential for moving forward in the field of comparative cognition. Follow-up studies could include more detailed measures of habitat structure and look at other potential selective drivers such as predation.

Bold and bright: shy and supple? The effect of habitat type on personality-cognition covariance in the Aegean wall lizard (Podarcis erhardii)

Animals exhibit considerable and consistent among-individual variation in cognitive abilities, even within a population. Recent studies have attempted to address this variation using insights from the field of animal personality. Generally, it is predicted that animals with "faster" personalities (bolder, explorative, and neophilic) should exhibit faster but less flexible learning. However, the empirical evidence for a link between cognitive style and personality is mixed. One possible reason for such conflicting results may be that personality-cognition covariance changes along ecological conditions, a hypothesis that has rarely been investigated so far. In this study, we tested the effect of habitat complexity on multiple aspects of animal personality and cognition, and how this influenced their relationship, in five populations of the Aegean wall lizard (Podarcis erhardii). Overall, lizards from both habitat types did not differ in average levels of personality or cognition, with the exception that lizards from more complex habitats performed better on a spatial learning task. Nevertheless, we found an intricate interplay between ecology, cognition, and personality, as behavioral associations were often habitat- but also year-dependent. In general, behavioral covariance was either independent of habitat, or found exclusively in the simple, open environments. Our results highlight that valuable insights may be gained by taking ecological variation into account while studying the link between personality and cognition.

Early social deprivation shapes neuronal programming of the social decision-making network in a cooperatively breeding fish

The early social environment an animal experiences may have pervasive effects on its behaviour. The social decision-making network (SDMN), consisting of interconnected brain nuclei from the forebrain and midbrain, is involved in the regulation of behaviours during social interactions. In species with advanced sociality such as cooperative breeders, offspring are exposed to a large number and a great diversity of social interactions every day of their early life. This diverse social environment may have life-long consequences on the development of several neurophysiological systems within the SDMN, although these effects are largely unknown. We studied these life-long effects in a cooperatively breeding fish, Neolamprologus pulcher, focusing on the expression of genes involved in the monoaminergic and stress response systems in the SDMN. N. pulcher fry were raised until an age of 2 months either with their parents, subordinate helpers and same-clutch siblings (+F), or with same-clutch siblings only (-F). Analysis of the expression of glucocorticoid receptor, mineralocorticoid receptor, corticotropin releasing factor, dopamine receptors 1 and 2, serotonin transporter and DNA methyltransferase 1 genes showed that early social experiences altered the neurogenomic profile of the preoptic area. Moreover, the dopamine receptor 1 gene was up-regulated in the preoptic area of -F fish compared to +F fish. -F fish also showed up-regulation of GR1 expression in the dorsal medial telencephalon (functional equivalent to the basolateral amygdala), and in the dorsolateral telencephalon (functional equivalent to the hippocampus). Our results suggest that early social environment has life-long effects on the development of several neurophysiological systems within the SDMN.

Using touchscreen equipped operant chambers to study animal cognition. Benefits, limitations, and advice

Operant chambers are small enclosures used to test animal behavior and cognition. While traditionally reliant on simple technologies for presenting stimuli (e.g., lights and sounds) and recording responses made to basic manipulanda (e.g., levers and buttons), an increasing number of researchers are beginning to use Touchscreen-equipped Operant Chambers (TOCs). These TOCs have obvious advantages, namely by allowing researchers to present a near infinite number of visual stimuli as well as increased flexibility in the types of responses that can be made and recorded. We trained wild-caught adult and juvenile great-tailed grackles (Quiscalus mexicanus) to complete experiments using a TOC. We learned much from these efforts, and outline the advantages and disadvantages of our protocols. Our training data are summarized to quantify the variables that might influence participation and success, and we discuss important modifications to facilitate animal engagement and participation in various tasks. Finally, we provide a “training guide” for creating experiments using PsychoPy, a free and open-source software that was incredibly useful during these endeavors. This article, therefore, should serve as a resource to those interested in switching to or maintaining a TOC, or who similarly wish to use a TOC to test the cognitive abilities of non-model species or wild-caught individuals.