Hylobatid communities: Changing views on pair bonding and social organization in hominoids

Abstract

Social organization involving pair bonding and two-adult groups is rare in mammals. Current sociobiological theory suggests that this grouping and behavior pattern is somewhat anomalous. The gibbons (genus Hylobates) are the only hominoids to exhibit pair bonds and two-adult groups. In this article I present an overview of the current issues in monogamy and pair-bond theory, and review traditional conceptualizations and the accumulated data relevant to gibbon social organization. The significance of hominoid behavioral phylogeny and population-wide studies is also considered. Recent findings indicate that pair-bonding and two-adult groups are not ubiquitous among the hylobatids. Many aspects of gibbon behavior and ecology do not conform to expectations of the conditions under which two-adult groups and/or pair-bonding patterns should evolve. A review of the information available from long-term and short-term studies of gibbons suggests an alternative way of viewing their socioecology. I propose that gibbons currently exist in variable communities that have arisen via ecological pressures and specific behavioral patterns from an ancestral multimale/multi-female grouping pattern. This social organization is not best characterized as "monogamous." This review also suggests that hominoid grouping patterns can be viewed as occurring along a continuum rather than as being discretely different units.

Adaptive response to sociality and ecology drives the diversification of facial colour patterns in catarrhines

“…Cercopithecids include some of the most social catarrhine species (for example, Mandrillus sphinx, with hordes of 800 þ individuals on record 16 ). The gibbons and siamangs of the SE Asian rainforests make up the Hylobatidae, characterized by more modestly sized groups and variable social dynamics that often include high degrees of pairbonding 17 . Finally, Hominidae 18 comprises four extant genera of great apes (and Homo, which was excluded from our sample).…”

Genetic variation in the vasopressin receptor 1a gene ( AVPR1A ) associates with pair-bonding behavior in humans

“…The pair bond is a critical element in the study of the evolution of primate social organization (21). Pair bonds among nonhuman primates are generally assessed by measures of partner specific affiliative interaction, proximity, and reciprocity between two individuals (22)(23)(24). Furthermore, the strength and stability of the bond is related to its persistence through time (25).…”

When Dads Help: Male Behavioral Care During Primate Infant Development

“…Among the hylobatids, pair-living is the prevalent, though not exclusive, social structure (Fuentes 2000 ;Lappan 2008 ;Reichard and Barelli 2008 ) . Despite this, direct male care of infants has not been reported for most gibbon species in the wild, with the notable exception being the largest species of the family, the siamang.…”