Behavioral characteristics of pair bonding in the black tufted-ear marmoset (Callithrix penicillata)

Abstract

The present study describes how the development of a pair bond modifies social, sexual and aggressive behavior. Five heterosexual pairs of marmosets, previously unknown to each other, were formed at the beginning of the study. At the onset of pairing, social, sexual, exploratory and aggressive behaviors were recorded for 40 min. The animals were then observed for 20 min, both in the morning and afternoon for 21 days. The frequency and/or duration of behaviors recorded on Day 1 were compared to those recorded at later observations. The behavior displayed shortly after pairing should be completely unaffected by the pair bond, while such a bond should be present at later observations. Thus, it was possible to determine how the behavior between the pair was modified by the development of a pair bond. Social behaviors increased from Day 1 to Days 2–6 and all subsequent days observed. Conversely, other behaviors, such as open mouth displays (usually considered to be an invitation to sexual activity), had a high frequency during the early part of cohabitation but declined towards the end. Consequently, pair bonding manifests itself in an increased intensity of social behaviors. It is suggested that the intrinsically rewarding properties of grooming and perhaps other social behaviors turn the pair mate into a positive incentive, activating approach and further interactions when possible. Thus, the pair bond may be a motivational state activated by the conditioned incentive properties of the partner. This notion can explain all forms of pair bonds, including those occurring between individuals of the same sex and in promiscuous species.

Sex Bias in Gut Microbiome Transmission in Newly Paired Marmosets (Callithrix jacchus)

“…In humans, marital spouses have higher gut microbiome similarities than siblings or nonrelated individuals (14). The data showing a female-to-male sex bias in horizontal microbe transmission presented here is consistent with behavioral evidence indicating that, in the first week or two after pairing, males exhibit higher rates of partner grooming than females and also engage in higher rates of anogenital investigation of the partner than females (25)(26)(27)(28)(29). The sex differences in investigatory behavior and contact with the partner could account for a more efficient transfer of multiple components of the microbiome from females to males.…”

“…First, we compared levels of microbial similarity in the two stages of the study (PRE versus POST) using the unweighted UniFrac distances by collapsing the time points to a single averaged point to indicate whether the pairing increased the gut microbiome similarity within the pair. We arranged the data in blocks from the period after the pairing stage, given the possible behavioral changes caused by the establishment of a pair bond (25,29,43,44) and the possible gut microbiome changes. Here, 14-day averages were calculated for each block.…”

“…These behavioral patterns could facilitate the transfer of microbial taxa between pairmates. In the first few weeks of pairing, there is also a sex bias in the directionality of social behavior, with males exhibiting higher rates than females of anogenital investigation, initiation of grooming, and initiation of spatial proximity in the first weeks after pairing relative to later phases of the social relationship (25)(26)(27)(28)(29).…”

Oxytocin facilitates fidelity in well-established marmoset pairs by reducing sociosexual behavior toward opposite-sex strangers

“…After eight weeks of cohabitation, which has been shown to be a more than adequate duration of time to allow for significant establishment of a stable social bond in marmosets (Ågmo et al, 2012), male and female marmosets underwent partner-preference testing. Proximity behavior, as well as sociosexual, aggressive/territorial, and communicative behaviors were observed during the partner-preference test.…”

The influence of androgenic steroid hormones on female aggression in ‘atypical’ mammals

“…Callitrichine primates show a socially monogamous structure, including close heterosexual bonds [55]. Callitrichine social systems are also characterized by low rates of intragroup aggression, yet adult females are typically dominant over adult males using standard food competition paradigms [56].…”