Is sexual monomorphism a predictor of polygynandry? Evidence from a social mammal, the collared peccary

Abstract

Sexual dimorphism is common in polygynous species, and there is clear evidence that both intra-sexual competition and female preferences can drive the evolution of large body size in males. In contrast, sexual monomorphism is often argued to reflect a relaxation of male mate competition or an intensification of resource competition among females. Alternatively, it might imply opportunities for females to circumvent or counteract male mate competition in a polygynandrous mating system. We test the prediction that sexual monorphism is associated with polygynandry in the collared peccary (Pecari tajacu, Tayassuidae), a social ungulate closely related to the old-world suids. The genetic mating system in the Tayassuidae is unknown, but its sexual monomorphism presents a striking contrast to the strong size dimorphism found in most Suidae, so that a departure from the polygynous system common in Suidae would be noteworthy. We characterized genetic relationships among adults within herds in three geographically distinct populations, assigned parents to 75 offspring, and tested for skew in individual reproductive success. Parentage assignment data indicated that multiple males sire offspring within a herd, and in the population for which genetic data were most complete, 19% of parentage assignments were potentially sired by extra-herd males. Some litters have multiple sires, and neither males nor females monopolized reproduction, even in small herds. This result supports our prediction and suggests that sexual monomorphism may either select for or be an evolutionary consequence of a promiscuous mating system.

Spatial patterns of the first groups of collared peccaries (Pecari tajacu) reintroduced in South America

“…In this study, only male 1 showed long distance dispersal (11 km) but still remained within the study area. This event is consistent with the male-biased dispersal for the species (Cooper et al 2010), where related males typically leave the group to join a neighboring herd (Byers and Bekoff 1981;Cooper et al 2011). The relatively short dispersal distances observed in the first group may be attributed to several factors: social-cohesion (as mentioned above), suitable habitat at the release site, sufficient acclimation in the pre-release enclosures, and the provision of supplemental food following release and during the winter period of low food abundance in 2016.…”

Sexual size dimorphism of group-living Mongolian gerbils Meriones unguicutalus (Muridae: Gerbillinae)

“…Likewise, territorial competition may make fish Tropheus moorii lose SSD (Odreitz & Sefc 2015). SSD is absent or low in many social mammals (Johnson & Macdonald 2001;Cooper et al 2011;Kappeler & Fichtel 2015). In contrast, data in this study demonstrated the existence of SSD in Mongolian gerbils, a small social rodent, and provided support for positive relationships between litter size and female carcass weight.…”

Society, demography and genetic structure in the spotted hyena

“…Social scientists have long-recognized the importance of social network theory in explaining human social (Rossiter et al 2006) Collared peccary, Pecari tajacu 0.01 )0.10-0.33 6 groups, 25 males (Cooper et al 2011) organizations (reviewed by Newman 2003b), but formal social network theory has only recently been applied to explain the structuring of animal societies (Krause et al 2007;Croft et al 2008;Wey et al 2008;Sih et al 2009). Although human social networks are often characterized by homophily, with individuals preferentially associating with others that possess traits similar to their own (e.g.…”