Relative Brain Volume of Carnivorans Has Evolved in Correlation with Environmental and Dietary Variables Differentially among Clades

Abstract

Carnivorans possess relatively large brains compared to most other mammalian clades. Factors like environmental complexity (Cognitive Buffer Hypothesis) and diet quality (Expensive-Tissue Hypothesis) have been proposed as mechanisms for encephalization in other large-brained clades. We examine whether the Cognitive Buffer and Expensive-Tissue Hypotheses account for brain size variation within Carnivora. Under these hypotheses, we predict a positive correlation between brain size and environmental complexity or protein consumption. Relative endocranial volume (PGLS residual from species mean body mass) and nine environmental and dietary variables were collected from the literature for 148 species of terrestrial and marine carnivorans. We found that the correlation between relative brain volume and environment and diet differed among clades, a trend consistent with other larger brained vertebrates (i.e., Primates, Aves). Mustelidae and Procyonidae demonstrate larger brains in species with higher quality diets, consistent with the Expensive-Tissue Hypothesis, while in Herpestidae correlations between relative brain size and environment are consistent with the Cognitive Buffer Hypothesis. Our results indicate that carnivorans may have evolved relatively larger brains under similar selective pressures as primates despite the considerable differences in life history and behavior between these two clades.

Endocast, brain, and bones: Correspondences and spatial relationships in squamates

“…Cranial endocasts are used to investigate the neuroanatomy of both extant and extinct vertebrates (e.g., Aristide et al, 2019; Benoit et al, 2017; Beyrand et al, 2019; Iwaniuk et al, 2020; Lautenschlager et al, 2018; Lynch & Allen, 2022; Schade et al, 2022; Weisbecker et al, 2021; Zhu et al, 2020). Virtual endocasts, generated by the increasingly widespread use of computed tomographic scanning, provide the potential to track evolution of brain external morphology through deep time, and the possibility to infer cognitive and sensory abilities, as well as behavior, of taxa (e.g., Balanoff & Bever, 2017; Dozo et al, 2022; Holloway et al, 2009; Jerison, 1973; Neubauer, 2014; Racicot, 2021).…”

Evolutionary ecomorphology for the twenty-first century: examples from mammalian carnivores

“…An increasing number of studies have come to focus on the relative volumes of different regions of the brain [61,62,65,[73][74][75][76][77] and have found correlations that were missed when looking at whole brain size. Enlargement of the frontal cortex correlates with sociality in hyenas, pantherines, canids and procyonids [61,65,[73][74][75][76] in family-level analyses, but the trend is erased when sampling across the order. This highlights the importance of looking for such correlations at smaller taxonomic scales, such as family or subfamily level.…”

“…The brain endocasts can provide pivotal insights into the evolution of sensation and cognition in extant and extinct carnivorans. Much of the focus has been on relative brain size, which correlates with diet [ 61 , 62 ], home-range size [ 63 ], problem solving ability [ 64 , 65 ], type of parental care [ 66 , 67 ], hibernation [ 68 ] and extinction risk [ 69 , 70 ]. Evidently, there is a plethora of forces involved in the evolution of the brain, but there have been few attempts to integrate these various factors into a broader understanding of what influences brain evolution [ 71 ].…”

“…One recent study investigates brain size evolution across carnivorans and finds a trade-off between a relatively large brain and the costs of having a large brain for the individual when adapting to new environments [ 72 ]. An increasing number of studies have come to focus on the relative volumes of different regions of the brain [ 61 , 62 , 65 , 73 – 77 ] and have found correlations that were missed when looking at whole brain size. Enlargement of the frontal cortex correlates with sociality in hyenas, pantherines, canids and procyonids [ 61 , 65 , 73 – 76 ] in family-level analyses, but the trend is erased when sampling across the order.…”