Personality traits, rank attainment, and siring success throughout the lives of male chimpanzees of Gombe National Park

Abstract

Personality traits in many taxa correlate with fitness. Several models have been developed to try to explain how variation in these traits is maintained. One model proposes that variation persists because it is linked to trade-offs between current and future adaptive benefits. Tests of this model’s predictions, however, are scant in long-lived species. To test this model, we studied male chimpanzees living in Gombe National Park, Tanzania. We operationalized six personality traits using ratings on 19 items. We used 37 years of behavioral and genetic data to assemble (1) daily rank scores generated from submissive vocalizations and (2) records of male siring success. We tested whether the association between two personality traits, Dominance and Conscientiousness, and either rank or reproductive success, varied over the life course. Higher Dominance and lower Conscientiousness were associated with higher rank, but the size and direction of these relationships did not vary over the life course. In addition, independent of rank at the time of siring, higher Dominance and lower Conscientiousness were related to higher siring success. Again, the size and direction of these relationships did not vary over the life course. The trade-off model, therefore, may not hold in long-lived and/or slowly reproducing species. These findings also demonstrate that ratings are a valid way to measure animal personality; they are related to rank and reproductive success. These traits could therefore be used to test alternative models, including one that posits that personality variation is maintained by environmental heterogeneity, in studies of multiple chimpanzee communities.

Whither dominance? An enduring evolutionary legacy of primate sociality

“…Fearless dominance is highly correlated with leadership/ authority and grandiose exhibitionism, but not entitlement/ exploitativeness (McDonald, Donnellan & Navarrete, 2012). Furthermore, narcissists' popularity starts strong and grows, but declines after some time (Leckelt, Küfner, Nestler & Back, 2015), resembling the relationship between dominance and rank in male chimpanzees (Weiss et al, 2023). The dominants of the past may have found a place in society as the less entitled narcissists of today.…”

“…chimpanzee females enter their own distinct hierarchy at a low rank, and queue to achieve higher status as higher ranking, usually older, females die (Foerster et al, 2016 ). Chimpanzee males enter their hierarchy around age 12, typically rise in rank before falling as they age, and lose the RHP necessary to win dyadic bouts (Weiss et al, 2023 ). Bonobo males follow a similar pattern, but their status is deeply intertwined with that of their mother (Furuichi, 1997 ; Surbeck, Mundry & Hohmann, 2010 ).…”

“…Moreover, both are assessed through entirely different techniques. A recent study that has grappled with this using long-term data from male chimpanzees found that trait dominance was significantly related to rank, throughout the individuals’ lifetimes, though this relationship was particularly strong during certain stages of the chimpanzees’ lives, specifically, early to middle adulthood (Weiss et al, 2023 ).…”

Does the primate face cue personality?

“…Personality structures of some species, however, include more than one Dominance-related dimension. Similar to chimpanzees (Weiss et al, 2023 ), rhesus macaque Assertiveness is related to dominance in social interactions (Kohn et al, 2016 ), whilst Confidence refers to confidence in the presence of environmental or social stressors (Adams et al, 2015 ). The characteristics of dominance hierarchies, assessed by observing outcomes of agonistic interactions, are usually expressed as rank (called “dominance status” in Altschul, Robinson, Coleman, Capitanio, & Wilson, 2019 ; “alpha status” in Lefevre et al, 2014 ; “agonistic dominance” in Martin et al, 2019 ).…”

“…Thirdly, we can utilise a comparative understanding of the role of faces in social cues or signals, by drawing comparisons amongst phylogenies of varying socio-ecology. Specifically, more studies on personality links to reproductive success (Brent et al, 2014 ; Masilkova, Boukal, Ash, Buchanan-Smith, & Konečná, 2022 ; Weiss et al, 2023 ) and the importance of personality in mate choice are needed. Studies that not only incorporate populations from western, educated, industrialised, rich and democratic populations but also people from indigenous communities could better aid the understanding of such selection pressures in humans.…”