Big Cat Coalitions: A Comparative Analysis of Regional Brain Volumes in Felidae

Abstract

Broad-based species comparisons across mammalian orders suggest a number of factors that might influence the evolution of large brains. However, the relationship between these factors and total and regional brain size remains unclear. This study investigated the relationship between relative brain size and regional brain volumes and sociality in 13 felid species in hopes of revealing relationships that are not detected in more inclusive comparative studies. In addition, a more detailed analysis was conducted of four focal species: lions (Panthera leo), leopards (Panthera pardus), cougars (Puma concolor), and cheetahs (Acinonyx jubatus). These species differ markedly in sociality and behavioral flexibility, factors hypothesized to contribute to increased relative brain size and/or frontal cortex size. Lions are the only truly social species, living in prides. Although cheetahs are largely solitary, males often form small groups. Both leopards and cougars are solitary. Of the four species, leopards exhibit the most behavioral flexibility, readily adapting to changing circumstances. Regional brain volumes were analyzed using computed tomography. Skulls (n = 75) were scanned to create three-dimensional virtual endocasts, and regional brain volumes were measured using either sulcal or bony landmarks obtained from the endocasts or skulls. Phylogenetic least squares regression analyses found that sociality does not correspond with larger relative brain size in these species. However, the sociality/solitary variable significantly predicted anterior cerebrum (AC) volume, a region that includes frontal cortex. This latter finding is despite the fact that the two social species in our sample, lions and cheetahs, possess the largest and smallest relative AC volumes, respectively. Additionally, an ANOVA comparing regional brain volumes in four focal species revealed that lions and leopards, while not significantly different from one another, have relatively larger AC volumes than are found in cheetahs or cougars. Further, female lions possess a significantly larger AC volume than conspecific males; female lion values were also larger than those of the other three species (regardless of sex). These results may reflect greater complexity in a female lion’s social world, but additional studies are necessary. These data suggest that within family comparisons may reveal variations not easily detected by broad comparative analyses.

Endocranial Development in the Coyote (<b><i>Canis latrans</i></b>) and Gray Wolf (<b><i>Canis lupus</i></b>): A Computed Tomographic Study

“…Regional brain volumes differ in behaviorally specialized species in comparison to close relatives possessing less specialized behaviors. Among carnivore fam- ilies, regional brain volume differences have been observed between selected species in Felidae [Sakai et al, 2016], Hyaenidae [Sakai et al, 2011], and Procyonidae [Arsznov and Sakai, 2013]. Regional brain volume differences have also been found between sexes in species with sexually dimorphic behaviors associated with differing social life histories including spotted hyenas [Arsznov, et al, 2010], lions [Arsznov and Sakai, 2012;Sakai et al, 2016], and coatimundis [Arsznov and Sakai, 2013].…”

Learning performance is influenced by the social environment in cichlid fishes.

“…Interest in comparative cognition has greatly increased in recent years, and the field is developing rapidly ( Heyes, 2017 ; Whiten, 2017 ; Whiten, Caldwell, & Mesoudi, 2016 ). Several studies have linked sociality to brain size ( Dunbar, 1992 ; Finlay & Darlington, 1995 ; Joffe & Dunbar, 1997 ; Pawłowski et al, 1998 ) and brain size to learning ability ( Benson-Amram et al, 2016 ; Deaner et al, 2007 ; Lodato & Arlotta, 2015 ; Lui et al, 2011 ; MacLean et al, 2014 ; Sakai et al, 2016 ; Shultz & Dunbar, 2010 ), yet there is still limited direct research into the relationship between sociality and learning ( Byrne & Bates, 2007 ; Hoppitt & Laland, 2013 ). We explored two conflicting hypotheses.…”

“…Evidence for the social brain hypothesis mostly comes from studies that have correlated brain size, especially neocortex size, with the degree of sociality ( Dunbar, 1992 ; Finlay & Darlington, 1995 ; Joffe & Dunbar, 1997 ; Pawłowski, Lowen, & Dunbar, 1998 ). In turn, several studies have correlated brain size and problem-solving ability ( Benson-Amram, Dantzer, Stricker, Swanson, & Holekamp, 2016 ; Deaner, Isler, Burkart, & van Schaik, 2007 ; Lodato & Arlotta, 2015 ; Lui, Hansen, & Kriegstein, 2011 ; MacLean et al, 2014 ; Sakai, Arsznov, Hristova, Yoon, & Lundrigan, 2016 ; Shultz & Dunbar, 2010 ).…”

The Brain Anatomy of the Brown Bear (Carnivora, Ursus arctos L., 1758) Compared to That of Other Carnivorans: A Cross-Sectional Study Using MRI

“…The issue can be elucidated by further cytoarchitectonic or gyrification studies in U. arctos. Interestingly, the rostral area to SCr is supposedly involved in social behavior, as studied in Crocuta crocuta (Holekamp et al, 2007; Sakai et al, 2011) and in Panthera leo (Sakai et al, 2016). The area would be substantially larger if GFD is also included.…”