The Island of Female Power? Intersexual Dominance Relationships in the Lemurs of Madagascar

Abstract

The extant primates of Madagascar (Lemuriformes) represent the endpoints of an adaptive radiation following a single colonization event more than 50 million years ago. They have since evolved a diversity of life history traits, ecological adaptations and social systems that rivals that of all other living primates combined. Their social systems are characterized by a unique combination of traits, including the ability of adult females to dominate adult males. In fact, there is no other group of mammals in which female dominance is so widespread. Yet, recent research has indicated that there is more interspecific variation in lemur intersexual relationships than previously acknowledged. Here, we therefore review and summarize the relevant literature, quantifying the extent of sex-bias in intersexual dominance relations documented in observational and experimental studies in captivity and the wild. Female dominance is often, but not always, implemented by spontaneous male submission in the absence of female aggression and linked to female sexual maturation. We connect the available evidence to the hypotheses that have been proposed to explain the evolution of female dominance among lemurs. The occurrence of female dominance in all lemur families and the interspecific variation in its extent indicate that it has evolved soon after lemurs colonized Madagascar – presumably in response to particular ecological challenges – and that it has since been reduced in magnitude independently in some taxa. Our study contributes important comparative information on sex roles from an independent primate radiation and provides general insights into the conditions, opportunities and obstacles in the evolution of female-biased power.

Sex and dominance: How to assess and interpret intersexual dominance relationships in mammalian societies

“…One of the novelties of the present study was the standardized application of several methods to calculate intersexual dominance across a range of mammalian species with different social systems. We found the degree of female dominance to vary continuously from strict male dominance to strict female dominance, adding to a growing number of studies (Hemelrijk et al, 2008(Hemelrijk et al, , 2020Rina Evasoa et al, 2019;Davidian et al, 2022;Kappeler et al, 2022) breaking with traditional binary categorizations into female-dominant vs. male-dominant species. Clearly, binary categories are insufficient to capture the variation in intersexual dominance relationships occurring both across and within species.…”

“…The dichotomous classification of species as either male-or female-dominated has been challenged by more recent studies indicating that these patterns only represent the endpoints of a continuum (Hemelrijk et al, 2008(Hemelrijk et al, , 2020Davidian et al, 2022;Kappeler et al, 2022). It is now more widely appreciated that there are taxa where members of one sex only win a proportion of all agonistic interactions with the members of the other sex or where they dominate only some, but not all, opposite-sex individuals (Surbeck and Hohmann, 2013;Young et al, 2017, Vullioud et al, 2019Hemelrijk et al, 2020).…”

Interrelationship among spatial cohesion, aggression rate, counter-aggression and female dominance in three lemur species

“…In general, hypotheses regarding female dominance over males in lemurs focus on the similar body size of the sexes as well as the greater effort that females invest in conflicts because of their higher energetic demand during reproduction (cost-asymmetry hypothesis, Dunham 2008). Until recently, variation among lemur species in the degree of female dominance over males has largely been ignored but recent results show that it is more variable than previously thought (Kappeler et al 2022). We propose here that the degree of female dominance over males may relate to differences in cohesion due to differences in the distribution of food and thus intensity of feeding competition.…”

“…The prior attribute hypothesis relates dominance to biological traits such as body size, where larger individuals are more likely to win than smaller ones (Chase and Seitz 2011). Yet, sometimes, smaller females are dominant over larger males in sexually dimorphic species, leading to variable patterns of intersexual dominance (Hemelrijk et al 2008(Hemelrijk et al , 2020Izar et al 2021;Kappeler et al 2022). The self-organisation hypothesis attributes this outcome to the winner-loser effect, which implies that following a conflict, winners are more likely to win their subsequent fight and vice versa for losers (Hsu et al 2006;Chase and Seitz 2011).…”

“…Yet, this effect has only been demonstrated when males are larger than females and, thus, are equipped with a higher initial dominance and intensity of aggression. In the present study, we examine how cohesion, and thus frequency of aggression, influences intersexual dominance in lemurs, where males and females do not differ in body size, and female dominance over males is common but differs in its degree among species (Eichmueller et al 2013;Rina Evasoa et al 2019;Kappeler et al 2022).…”