Genetic Characterization of MAOA and OXTR in Western Lowland Gorillas ( Gorilla gorilla gorilla )

Social behavior in primates varies widely within and across species, and growing work in behavioral genetics highlights the value of documenting sequence variation in neurobiologically relevant genes. However, for great apes, knowledge of individual genetic variation for behavior-associated loci remains limited. We characterized variation in the MAOA promoter VNTR and the OXTR SNP rs35062132 in 12 western lowland gorillas (Gorilla gorilla gorilla) and incorporated an exploratory comparison between genotypes and individual sociability. Sociability was quantified from 25 10-min focal follows per subject, including proximity, affiliative, and agonistic behaviors. We identified multiple MAOA VNTR genotypes, including a 0-repeat allele not previously reported in gorillas, indicating greater regulatory-region diversity than has been described for this species. No polymorphism was detected at OXTR rs35062132, although several fixed differences from other great ape species were identified at nearby nucleotide positions. Behavioral observations revealed individual differences in sociability; however, the presence of multiple previously undescribed MAOA VNTR genotypes with unknown functional consequences limited interpretability of genotype-behavior associations. We provide the first detailed description of MAOA promoter variation in gorillas and demonstrate sequence conservation in the OXTR region analyzed. These data underscore the importance of future research on gorilla social variation and comparative primate genomics.