Post-conflict behaviors are a crucial component of primate sociality, yet are difficult to study ... more Post-conflict behaviors are a crucial component of primate sociality, yet are difficult to study in the wild. We evaluated the presence and timing of reconciliation, victim-solicited and unsolicited third-party affiliation, and secondary and redirected aggression following observed agonistic interactions among 38 wild gelada monkeys (Theropithecus gelada) in eight one-male, multi-female units at Guassa, Ethiopia, from April to August 2018. We also report background rates of aggression and patterns of agonistic interactions and post-conflict behaviours among wild geladas relative to possible mediating factors for each conflict, including social rank disparity, kinship type, sex, age class, conflict intensity, and conflict decidedness. Across 55 post-conflict and 55 subsequent matched-control focal follows, we found no evidence for post-conflict reconciliation, third-party affiliation, secondary aggression, or redirected aggression. These findings contrast with previous studies of captive geladas, which find that individuals often reconcile after fights and frequently exhibit unsolicited third-party affiliation when reconciliation does not occur. Our results from wild geladas point to possible populational differences in behavioral Badge earned for open practices: Open Data Badge. Experiment materials and data are available in the repository at
Following the introduction of DNA fingerprinting in the 1980s, studies have repeatedly revealed m... more Following the introduction of DNA fingerprinting in the 1980s, studies have repeatedly revealed mis-matches between the mating system inferred from social behaviour and the mating system revealed through genetic relationships. In this study, we examined the occurrence of extragroup paternities (EGPs) in gelada monkeys at Guassa, Ethiopia and explored how EGPs may be acquired in this species, which is conventionally considered to have a single breeding male (‘leader’) per social group (‘unit’). We found that while leaders sired most offspring, a substantial proportion (17 of 88 offspring, 19%) were sired by extra-unit males. Offspring were more likely to be sired by extra-unit males when they were: (1) conceived in the 6 months following the start of peak rainfall (July-December) and (2) the first successful conception for a mother. Furthermore, eight of the 17 extra-unit paternities were directly or indirectly the result of a single infertile leader, indicating that infertility plays an important role in the occurrence of EGPs. Compiling published data revealed that the 19% EGP rate observed among Guassa geladas was also the median for polygynous nonhuman primates (range 0 - 57%, N = 5 populations), in contrast to geladas in the Simien Mountains, where EGPs are absent or rare. Thus, intraspecific variation in EGP rates in geladas encompasses much of the range described across polygynous primates more broadly. The Guassa gelada EGP rate was similar to the median rate reported for mammals. Primates generally had a lower median rate of EGPs, more similar to the median rate reported for birds. Understanding variation in EGP rates requires understanding the outcomes of competing interests of males and females within the same species, as well as how these features contribute to the evolution of social systems and influence variation in EGP rates at higher taxonomic levels.
Ever since Darwin, questions about humans have driven sexual selection research. While studies of... more Ever since Darwin, questions about humans have driven sexual selection research. While studies of other organisms are often justified as useful for improving understanding of humans, humans themselves can be useful models. Although humans present some drawbacks as model organisms (complicated societies, slow reproduction and strong ethical constraints on experimental options), humans nonetheless offer many advantages (being abundant, accessible and having detailed historical records for some populations). As an additional challenge, humans exhibit a rather puzzling combination of traits. Some traits (pair-bonding, biparental care and modest sexual dimorphism in body size) suggest selection for monogamous mating, while other traits (including sexual dimorphism in body composition and appearance) suggest selection for polygyny. Such puzzles have motivated research on other species, resulting in a rich set of comparative data that provides insights into humans and other species. Recent...
American journal of physical anthropology, May 1, 2017
The birth process has been studied extensively in many human societies, yet little is known about... more The birth process has been studied extensively in many human societies, yet little is known about this essential life history event in other primates. Here, we provide the most detailed account of behaviors surrounding birth for any wild nonhuman primate to date. Over a recent ∼10-year period, we directly observed 15 diurnal births (13 live births and 2 stillbirths) among geladas (Theropithecus gelada) at Guassa, Ethiopia. During each birth, we recorded the occurrence (or absence) of 16 periparturitional events, chosen for their potential to provide comparative evolutionary insights into the factors that shaped birth behaviors in humans and other primates. We found that several events (e.g., adopting standing crouched positions, delivering infants headfirst) occurred during all births, while other events (e.g., aiding the infant from the birth canal, licking infants following delivery, placentophagy) occurred during, or immediately after, most births. Moreover, multiparas (n = 9) we...
Post-conflict behaviors are a crucial component of primate sociality, yet are difficult to study ... more Post-conflict behaviors are a crucial component of primate sociality, yet are difficult to study in the wild. We evaluated the presence and timing of reconciliation, victim-solicited and unsolicited third-party affiliation, and secondary and redirected aggression following observed agonistic interactions among 38 wild gelada monkeys (Theropithecus gelada) in eight one-male, multi-female units at Guassa, Ethiopia, from April to August 2018. We also report background rates of aggression and patterns of agonistic interactions and post-conflict behaviours among wild geladas relative to possible mediating factors for each conflict, including social rank disparity, kinship type, sex, age class, conflict intensity, and conflict decidedness. Across 55 post-conflict and 55 subsequent matched-control focal follows, we found no evidence for post-conflict reconciliation, third-party affiliation, secondary aggression, or redirected aggression. These findings contrast with previous studies of captive geladas, which find that individuals often reconcile after fights and frequently exhibit unsolicited third-party affiliation when reconciliation does not occur. Our results from wild geladas point to possible populational differences in behavioral Badge earned for open practices: Open Data Badge. Experiment materials and data are available in the repository at
Following the introduction of DNA fingerprinting in the 1980s, studies have repeatedly revealed m... more Following the introduction of DNA fingerprinting in the 1980s, studies have repeatedly revealed mis-matches between the mating system inferred from social behaviour and the mating system revealed through genetic relationships. In this study, we examined the occurrence of extragroup paternities (EGPs) in gelada monkeys at Guassa, Ethiopia and explored how EGPs may be acquired in this species, which is conventionally considered to have a single breeding male (‘leader’) per social group (‘unit’). We found that while leaders sired most offspring, a substantial proportion (17 of 88 offspring, 19%) were sired by extra-unit males. Offspring were more likely to be sired by extra-unit males when they were: (1) conceived in the 6 months following the start of peak rainfall (July-December) and (2) the first successful conception for a mother. Furthermore, eight of the 17 extra-unit paternities were directly or indirectly the result of a single infertile leader, indicating that infertility plays an important role in the occurrence of EGPs. Compiling published data revealed that the 19% EGP rate observed among Guassa geladas was also the median for polygynous nonhuman primates (range 0 - 57%, N = 5 populations), in contrast to geladas in the Simien Mountains, where EGPs are absent or rare. Thus, intraspecific variation in EGP rates in geladas encompasses much of the range described across polygynous primates more broadly. The Guassa gelada EGP rate was similar to the median rate reported for mammals. Primates generally had a lower median rate of EGPs, more similar to the median rate reported for birds. Understanding variation in EGP rates requires understanding the outcomes of competing interests of males and females within the same species, as well as how these features contribute to the evolution of social systems and influence variation in EGP rates at higher taxonomic levels.
Ever since Darwin, questions about humans have driven sexual selection research. While studies of... more Ever since Darwin, questions about humans have driven sexual selection research. While studies of other organisms are often justified as useful for improving understanding of humans, humans themselves can be useful models. Although humans present some drawbacks as model organisms (complicated societies, slow reproduction and strong ethical constraints on experimental options), humans nonetheless offer many advantages (being abundant, accessible and having detailed historical records for some populations). As an additional challenge, humans exhibit a rather puzzling combination of traits. Some traits (pair-bonding, biparental care and modest sexual dimorphism in body size) suggest selection for monogamous mating, while other traits (including sexual dimorphism in body composition and appearance) suggest selection for polygyny. Such puzzles have motivated research on other species, resulting in a rich set of comparative data that provides insights into humans and other species. Recent...
American journal of physical anthropology, May 1, 2017
The birth process has been studied extensively in many human societies, yet little is known about... more The birth process has been studied extensively in many human societies, yet little is known about this essential life history event in other primates. Here, we provide the most detailed account of behaviors surrounding birth for any wild nonhuman primate to date. Over a recent ∼10-year period, we directly observed 15 diurnal births (13 live births and 2 stillbirths) among geladas (Theropithecus gelada) at Guassa, Ethiopia. During each birth, we recorded the occurrence (or absence) of 16 periparturitional events, chosen for their potential to provide comparative evolutionary insights into the factors that shaped birth behaviors in humans and other primates. We found that several events (e.g., adopting standing crouched positions, delivering infants headfirst) occurred during all births, while other events (e.g., aiding the infant from the birth canal, licking infants following delivery, placentophagy) occurred during, or immediately after, most births. Moreover, multiparas (n = 9) we...
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Papers by Carrie Miller