Cognition in an Ever-Changing World: Climatic Variability Is Associated with Brain Size in Neotropical Parrots

Abstract

Research on the conditions favoring the evolution of complex cognition and its underlying neural structures has increasingly stressed the role of environmental variability. These studies suggest that the ability to learn, behave flexibly and innovate would be favored under unpredictable variations in the availability of resources, as it would enable organisms to adjust to novel conditions. Despite the growing number of studies based on the idea that larger-brained organisms would be better prepared to cope with environmental challenges, direct testing of the association between brain size and environmental variability per se remains scant. Here we focus on Neotropical parrots as our model group and test the hypothesis that if relatively larger brains were favored in climatically variable environments, larger-brained species should currently tolerate a higher degree of environmental uncertainty. Although we show that there are also other factors underlying the dynamics of brain size variation in this group, our results support the hypothesis that proportionally larger-brained species are more tolerant to climatic variability, both on a temporal and spatial scale. Additionally, they suggest that the differences in relative brain size among Neotropical parrots represent multiple, recent events in the evolutionary history of the group, and are particularly tied to an increased dependence on more open and climatically unstable habitats. As this is the first study to present evidence of the link between brain size and climatic variability in birds, our findings provide a step towards understanding the potential benefits underlying variation in brain size and the maintenance of highly enlarged brains in this and other groups.

Effects of Seasonality on Brain Size Evolution: Evidence from Strepsirrhine Primates

“…Thus, we would expect selection to favor relatively large brains in seasonal habitats. This hypothesis is supported by a comparative study on Neotropical parrots, which found a positive correlation between climatic variability and brain size (Schuck-Paim et al 2008). Moreover, migrating birds have smaller brains than nonmigrating species (Winkler et al 2004;Sol et al 2005), which the authors interpret as a cognitive buffer effect in the residential species.…”

Relative Brain Size and Its Relation with the Associative Pallium in Birds

“…Much of past effort has been devoted to assessing whether the existing variation in brain size among species predicts differences in cognitively demanding behaviours. This has yielded ample evidence that larger brains are associated with enhanced domain-general cognition [Lefebvre et al, 1997;Reader and Laland, 2002;Reader et al, 2011;Benson-Amram et al, 2016] and function to facilitate behavioural adjustments to socio-environmental changes [Reader and Laland, 2002;Sol et al, 2005Sol et al, , 2007Sol, 2009;Schuck-Paim et al, 2008]. Despite the progress, the biological significance of brain size variation across species is not exempt from criticism [Healy and Rowe, 2007].…”

Environmental Influences on Neuromorphology in the Non-Native Starling <b><i>Sturnus vulgaris</i></b>

“…This "cognitive buffer hypothesis" [Sol, 2009] suggests that larger brains allow animals to withstand seasonal or spatial variation in resource availability. Consistent with this interpretation, South American parrot species inhabiting climatically more variable environments tend to have larger brain sizes [Schuck-Paim et al, 2008]. However, there are a number of problems associated with such broad interspecific comparisons [Gonda et al, 2013].…”

“…Significant variation in morphological parameters has been identified in contemporary populations across environmental clines [Cardilini et al, 2016]. Potentially, multiple processes may influence neuromophology in starlings over habitats with significant environmental variation, driven by differences in resource distribution and predictability between habitats [Schuck-Paim et al, 2008;Kozlovsky et al, 2014]. Coastal populations have higher densities of starlings and are characterized by wetter conditions with the suggestion that foraging resources may be more widely distributed.…”