First evidence of yawn contagion in a wild monkey species

Abstract

Yawn contagion occurs when individuals yawn in response to the yawn of others (triggers). This is the first account of yawn contagion in wild geladas (Theropithecus gelada), a monkey species that shows yawn contagion in captivity and is organized in core units (one-male/bachelor groups) forming multilevel associations. In a population of geladas from the Kundi plateau (Ethiopia) we found that the yawning response was highest when geladas could perceive a triggering yawn, which confirms that yawn contagion is present in the wild. Yawn duration, mouth-opening degree and presence/absence of vocalisation (possibly modulating yawn detectability) did not affect the likelihood of contagion. Males and females, known to be both implicated in movement initiation within groups, were similarly powerful as yawn triggers. Instead, group membership and responder sex had a significant role in shaping the phenomenon. Yawn contagion was highest between individuals belonging to different core units and males were most likely to respond to others’ yawns. Because males have a non-negligible role in inter-group coordination, our results suggest that yawn contagion may have a communicative function that goes beyond the basic unit level.

Yawn contagion in bonobos: Another group, another story

“…We did so as in the fourth minute there is the highest probability of autocorrelation (a yawn performed by a subject at t 0 increases the probability to have another yawn by the same subject at t (0+X) where X is the increasing unit of time; Kapitány & Nielsen, 2017 ). To further reduce autocorrelation issues, in case of a yawning chain (i.e., several yawns emitted in a row by the same subject during 3 min, with no other subject yawning), we considered as a response only the first yawn emitted after the last triggering yawn (Gallo et al, 2021 ). When more than one yawning response occurred from different subjects, the first responder would become a trigger and we noted whether—for each responder—the triggering stimulus came from one or multiple triggers within the fixed time window.…”

“…In non‐hominid primates, yawn contagion studies show mixed results (cf. geladas, Theropithecus gelada , Gallo et al, 2021 ; Palagi et al, 2009 ; Tonkean macaque, Macaca tonkeana , Palagi & Norscia, 2019 ; but see: stump‐tailed macaques, Macaca arctoides : Paukner & Anderson, 2006 ; Japanese macaque, Macaca fuscata , Palagi & Norscia, 2019 ). Finally, no evidence of yawn contagion was found in strepsirrhines ( Lemur catta and Varecia variegata , Reddy et al, 2016 ) even though contagious yawning is present in non primates (Gallup et al, 2015 ; for review: Palagi et al, 2020 ).…”

Bridging Captive and Wild Studies: Behavioral Plasticity and Social Complexity in Theropithecus gelada

“…More recently, thanks to the use of video-cameras, Gallo et al [91] were able to collect standardized data on yawn contagion in the wild (Figure 4). Of course, compared to the captive study, the wild one relied on a reduced dataset.…”

“…The authors suggest that, within the OMU, yawn contagion might foster synchronization between groupmates sharing strong bonds (i.e., grooming), as suggested by the captive approach [90]. At an upper level, beyond the "OMU boundaries", yawn contagion may help promote the daily activity coordination of different OMUs, as suggested by the wild approach [91]. Yawn contagion is one of the most iconic examples of a behavior that was first detected and documented in captivity and then 'validated' in the wild.…”

Interspecific Contagious Yawning in Humans

“…One experiment also indicated contagious yawning among a subline of high-frequency-yawning rats [ 35 ]. Observational studies of the naturalistic frequency of yawning also suggest contagion among gelada baboons [ 36 , 37 ], wolves [ 38 ], domesticated pigs [ 39 ], and African lions [ 17 ]. In addition, evidence for yawn contagion has been reported among African elephants [ 40 ], domesticated sheep [ 41 ], and elephant seals [ 42 ].…”