Premium
Even adult sex ratios in lemurs: Potential costs and benefits of subordinate males in Verreaux's sifaka ( Propithecus verreauxi ) in the Kirindy Forest CFPF, Madagascar
Author(s) -
Kappeler Peter M.,
Mass Vanessa,
Port Markus
Publication year - 2009
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.21091
Subject(s) - lemur , demography , biology , aggression , mating , lemur catta , sex ratio , reproductive success , ecology , primate , psychology , social psychology , population , sociology
Optimal group size and composition are determined by both the costs and benefits of group living for the group's members. Verreaux's sifakas ( Propithecus verreauxi ), a diurnal lemur, form multimale multifemale groups with the tendency toward even adult sex ratios despite a small average number of females per group. The unexpected presence of multiple adult males may be explained by tolerance of other group members if subordinate males provide benefits to the group that outweigh the costs associated with their presence. Results based on both demographic data collected over a 13‐year period and behavioral observations suggest that subordinate males provide no benefits in terms of infant survival and defense against group takeover by outside males. Although groups with more males are more likely to win intergroup encounters, subordinate males do not participate in these encounters more often than expected. Subordinate males are not costly to other group members in terms of direct intragroup feeding competition, but aggression rates between dominant and immigrated subordinate males increase in the mating season. Even though subordinate males provide very few benefits to the group, they are not very costly either and thus may be tolerated by resident females and dominant males. This tolerance may help to partially explain the tendency towards their unusual adult sex ratio. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.