When close relatives mate, offspring are expected to suffer fitness consequences due to inbreeding depression. Inbreeding has previously been quantified in two ways: using a sufficiently large panel of markers or deep and complete pedigrees over several generations. However, the application of both approaches is still limited by the challenge of compiling such data for species with long generation times, such as primates. Here, we assess inbreeding in rhesus macaques living on Cayo Santiago (Puerto Rico), a population genetically isolated since 1938, but descendant of a large set of presumably unrelated founders. Using comprehensive genetic data, we calculated inbreeding coefficients (F) for 2669 individuals with complete three generation pedigrees and 609 individuals with complete four generation pedigrees. We found that 0.79 and 7.39% of individuals had an F > 0 when using data from three and four generation pedigrees, respectively. No evidence of an increase in inbreeding over the study period (up to 23 years) was found. Furthermore, the observed mean relatedness of breeding pairs differed significantly from the distribution of parental relatedness expected as simulated based on previous reproductive data, suggesting that kin generally avoid breeding with each other. Finally, inbreeding was not a predictor of early mortality measured as survival until weaning and sexual maturation, respectively. Our results remain consistent with three estimators of inbreeding (standardized heterozygosity, internal relatedness, and homozygosity by loci) using up to 42 highly polymorphic microsatellites for the same set of individuals. Together, our results demonstrate that close inbreeding may not be prevalent even in populations isolated over long periods when mechanisms of inbreeding avoidance can operate.Significance statementWhen close relatives mate, offspring may suffer from such inbreeding, e.g., via lower survival and/or fertility. Using (i) a large panel of genetic markers and (ii) complete three or four generation pedigrees, respectively, we show that incidences of inbreeding in a long-lived primate population are rare, even after genetic isolation for 75 years. Moreover, our simulations suggest that kin in our population generally avoid breeding with each other. Finally, the few inbred individuals detected in our large sample did not suffer from lower survival. Given that many animal species face dramatic habitat loss combined with critical population declines, our study provides important implications for conservation biology in general and for population management in particular.Electronic supplementary materialThe online version of this article (doi:10.1007/s00265-016-2236-6) contains supplementary material, which is available to authorized users.

Male reproductive strategies have been well-studied in primate species where males' ability to 35 monopolize reproductive access is high. Less is known about species where males cannot 36 monopolize mating access. Vervet monkeys (Chlorocebus pygerythrus) are interesting in this 37 regard as female co-dominance reduces the potential for male monopolization. Under this 38 condition, we assessed whether male dominance rank still influences male mating and 39 reproductive success, by assigning paternities to infants in a population of wild vervets in the 40 Eastern Cape, South Africa. To determine paternity, we established microsatellite markers 41 from non-invasive fecal samples via cross-species amplification. In addition, we evaluated 42 male mating and reproductive success for three groups over four mating seasons. We 43 identified 21 highly polymorphic microsatellites (number of alleles = 7.5±3.1 (mean±SD), 44 observed heterozygosity = 0.691±0.138 (mean±SD)) and assigned paternity to 94 of 97 45 sampled infants (96.9%) with high confidence. Matings pooled over four seasons were 46 significantly skewed across three groups, although skew indices were low (B index = 0.023 to 47 0.030) and mating success did not correlate with male dominance. Paternities pooled over 48 four seasons were not consistently significantly skewed (B index = 0.005 to 0.062), with high-49 ranking males siring more offspring than subordinates only in some seasons. We detected six 50 cases of extra-group paternity (6.4%), and four cases of natal breeding (4.3%). Our results 51 suggest that alternative reproductive strategies besides priority of access for dominant males 52 are likely to affect paternity success, warranting further investigation into the determinants of 53 paternity among species with limited male monopolization potential.