Social fish have larger brains and greater relative telencephalon sizes: support for the social brain hypothesis from wild, intraspecific comparisons

The Social Brain Hypothesis posits that complex social environments drive the evolution of larger brains and the enlargement of specific brain regions. Among species comparisons often report contrasting relationships between social complexity and brain size, potentially due to confounding effects of phylogeny, morphology, and ecology. Here, we explore this relationship in a single fish species, combining behavioural observations and brain measurements of two wild populations of the cichlid Neolamprologus brevis, which occupy similar ecological niches across its range but inhabit contrasting social environments depending on local shelter abundance. This dataset contains behavioural and neuroanatomical measurements from two wild populations of the shell-dwelling cichlid Neolamprologus brevis used to test the social brain hypothesis. The data include total brain volume, volumes of five brain regions (telencephalon, optic tectum, cerebellum, medulla, and hypothalamus), body weight, sex, and population identity for 43 individuals. Neighbour density and behaviour frequency summaries are included. The dataset also contains R code used for all statistical analyses and figure generation. Data can be reused for comparative neuroanatomy, behavioural ecology, and allometric scaling analyses. No ethical or legal restrictions apply.