Let's Call A Truce…For Now: The Silent Bared‐Teeth Face Expression in Mandrills (Mandrillus sphinx) During Baseline and Post‐Conflict Conditions

Abstract

The distinction between signals that are friendly and those that are nonaggressive but motivationally neutral (signals of benign intent, SBIs) has not often been well elucidated in the literature. Although both signals occur in similar contexts, friendly signals should be exchanged more often between animals with good relationships whereas SBIs should be more commonly exchanged between animals with poor or unpredictable relationships. The importance of this distinction is particularly salient in the post-conflict context, because the two different types of signals may have disparate distributions and functions. This study examines the nature of the silent bared-teeth face (SBTF) in captive mandrills (Mandrillus sphinx) both during baseline interactions and following aggressive conflicts. We report that the SBTF is most commonly exchanged between mandrills with high rates of agonism. In addition, the SBTF is the most common post-conflict signal exchanged, and the mandrills exchanging this signal after fighting also have poor relationships. We conclude that, although one must be careful in generalizing from studies of captive populations, the mandrill SBTF observed in this study is most accurately classified as a signal of benign intent, but not a truly friendly signal and discuss problems with interpreting post-conflict data without distinguishing between these types of signals.

High-Ranking Geladas Protect and Comfort Others After Conflicts

“…In contrast, other species of the Macaca genus, which have more despotic social relationships, show high levels of redirection and the absence of third party affiliation 45 , 80 – 82 . Our results also contrast with the function of spontaneous third-party affiliation found in mandrills ( Mandrillus sphinx ), a more despotic species 63 , 83 . Schino and Marini 63 found that victims received most affiliation from those bystanders that were frequently the target of redirection and that bystander affiliation reduced the probability of redirected aggression.…”

“…As far as we know, only two studies have explicitly tested this hypothesis in species of monkeys with differing social styles. Third party affiliation in the egalitarian Tonkean macaque protects the victim from further attacks 45 , whereas such effect was not found in mandrills 63 , a species with a more despotic social style 83 . The apparently contrasting results deriving from these studies are in line with the different social dynamics characterizing the two species and, more specifically, with their different levels of tolerance sensu 84 .…”

Towards a social functional account of laughter: Acoustic features convey reward, affiliation, and dominance

“…Spontaneous and rewarding co-laughter may indicate a secure social bond, while affiliative co-laughter may indicate bond maintenance or establishment is occurring. Indeed, such a distinction occurs in the facial displays of mandrill monkeys [ 80 ].…”

Morphological variants of silent bared‐teeth displays have different social interaction outcomes in crested macaques (Macaca nigra)

“…However, in contrast with the research on human facial expressions, little consideration has been given to the potential for subtle variation in primate facial expressions. SBT, for example, has been regarded as a single facial expression both in classic descriptive work (e.g., van Hooff, 1967) and several more recent ethological studies (e.g., Beisner & McCowan, 2014; Flack & de Waal, 2007; Otovic, Partan, Bryant, & Hutchinson, 2014). This assumption has then been carried forward into studies of the evolution of communication.…”