Maternal rank influence on rank acquisition and social integration in wild dispersing male vervet monkeys

Abstract

Juvenile life is marked by behavioural and physiological changes that are shaped by the physical and social environment that an individual experiences. In mammals, an individual’s social experience is closely linked with that of its mother. This study investigated the effects of maternal dominance rank and juvenile social experience on later life rank attainment and social integration in male vervet monkeys. Maternal ranks of ten study subjects were calculated during their juvenile period in their natal groups. The ranks that they attained and their extent of social integration - degree, strength and eigenvector centrality - were calculated one year after immigration into their new groups. The results indicated that maternal rank significantly predicts later life rank attainment. Individuals with high-ranking mothers showed negative power trajectories and attained lower ranks, and individuals with low-ranking mothers showed positive rank trajectories and attained higher ranks. No significant relationship was observed between maternal rank and social integration in this sample but high rank attainment and degree measures were observed to correlate. These results support the idea of birth sex ratio bias as low-ranking females would benefit more from having sons rather than daughters whereas high-ranking females would benefit more from having daughters rather than sons.