Abstract
Natal dispersal may have considerable social, ecological and evolutionary consequences. While species-specific dispersal strategies have received much attention, individual variation in dispersal decisions and its fitness consequences remain poorly understood. We investigated causes and consequences of natal dispersal age in rhesus macaques (Macaca mulatta), a species with male dispersal. Using long-term demographic and genetic data from a semi-free ranging population on Cayo Santiago, Puerto Rico, we analysed how the social environment such as maternal family, group and population characteristics affected the age at which males leave their natal group. While natal dispersal age was unrelated to most measures of group or population structure, our study confirmed earlier findings that sons of high-ranking mothers dispersed later than sons of low-ranking ones. Natal dispersal age did not affect males’ subsequent survival, but males dispersing later were more likely to reproduce. Late dispersers were likely to start reproducing while still residing in their natal group, frequently produced extra-group offspring before natal dispersal and subsequently dispersed to the group in which they had fathered offspring more likely than expected. Hence, the timing of natal dispersal was affected by maternal rank and influenced male reproduction, which, in turn affected which group males dispersed to.
Highlights
Lower lifetime reproductive success[18]
Sons of high-ranking mothers dispersed, on average, one year later than sons of low-ranking mothers (Table 1, Fig. 1). Sons who lost their mother before maturation tended to disperse earlier than those whose mother was present throughout both infancy and early puberty (Table 1). Males dispersed from their natal group at a later age if more groups were present on Cayo Santiago (Table 1, Fig. 2)
Based on 45 years of demographic and 22 years of genetic data on multiple social groups of rhesus macaques, the present study provides the first comprehensive analysis of the socioecological causes in conjunction with the fitness consequences of individual dispersal decisions in a non-human primate
Summary
Lower lifetime reproductive success[18]. Other studies in birds point towards increased reproductive opportunities and lifetime reproductive success associated with delayed natal dispersal (Siberian jays Perisoreus infaustus[19]; Seychelles warblers Acrocephalus sechellensis[20]). The present study investigated the social mediators and lifetime fitness consequences of natal dispersal decisions in the rhesus macaques of Cayo Santiago, a population that is ideally suited for studying dispersal. Rhesus macaques live in multi-male, multi-female groups, with most males dispersing from their natal group around puberty, i.e. when they are four to five years old[25,26]. Studies on a small number of rhesus macaques ranging freely at La Parguera, Puerto Rico, indicated that males frequently dispersed with peers and tended to disperse into groups with a higher rate of females[25] or into groups containing older maternal brothers[30]. To better understand the social mechanisms mediating natal dispersal and its fitness effects we explored individual variation in natal dispersal age in a powerful long-term data set of 45 years on over 900 individual males. We investigated how reproductive patterns mediated by the timing of natal dispersal affected the decision where to disperse to
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