Is it for real? Structural differences between play and real fighting in adult chimpanzees (Pan troglodytes)

Abstract

In primates, as well as in other mammals, play fighting (PF) is a complex form of playful activity that is structurally similar to real fighting (RF) and may also be used in a competitive way. Here, we verify the structural key differences that can distinguish PF from RF in adult chimpanzees (Pan troglodytes). We collected 962 h of video recording on 30 adult individuals belonging to four chimpanzee groups (Mona Chimpanzee Sanctuary, Spain; La Vallée des Singes and ZooParc de Beauval, France). We applied different indices—two of which were borrowed from the ecological measures of biodiversity—to test for structural differences between PF (345 sessions) and RF (461 sessions) in the levels of behavior repetition (Repeatability of Same Behavior Index, RSBI), distribution uniformity (Pielou Index, J), variability (Shannon Index, H′) and, symmetry (i.e., reciprocal exchange of offensive/defensive behaviors; Asymmetry Index, AI). Moreover, we compared the session duration between PF and RF. We found that duration and RSBI were higher in PF than RF while AI was higher in RF than PF. No difference was found between J and H′. Interestingly, both females and males maintained similar ranking positions (determined via Normalized David's scores) in RF and PF. Our study indicates that session duration, behavior repetition, and symmetry can be distinctive structural key features of PF whereas dominance role‐reversal, behavior variability, and distribution uniformity were not. PF in adult chimpanzees may have elements of serious contexts (e.g., absence of role‐reversal as in RF) which is in line with the view that play is a blended, multifunctional behavior deriving from the re‐combination of different behavioral systems. Our findings highlight the need to investigate play structure and manifestation in a nuanced way to better understand the actual motivation that underlies what appears to be play.

Rapid facial mimicry in Platyrrhini: Play face replication in spider monkeys (Ateles fusciceps, Ateles hybridus, and Ateles paniscus)

“…Continuing competitive play sessions can enhance the social assessment process among players (Fagen, 1981;Paquette, 1994;Thompson, 1998). Through play, individuals can gather valuable information about the nature of their relationships (cooperative or competitive) as well as assess each other's physical and cognitive capacities (Cordoni et al, 2021(Cordoni et al, , 2023.…”

“…Carlo randomization H = 3.881, df = 2, p = 0.149). Two consecutive sessions were considered as different if the play interruption lasted at least 10 s (Cordoni et al, 2021(Cordoni et al, , 2023. Playful behavioral patterns were distinguished as offensive (i.e., behavioral patterns aimed at attacking and pursuing the partner), defensive (i.e., behavioral patterns aimed at eluding an attack, freeing oneself from a playmate's grab or fleeing from the pursuit by the partner), and neutral (i.e., behavioral patterns neither offensive nor defensive; Cordoni et al, 2021Cordoni et al, , 2023.…”

“…Play behavior-by recruiting and differently recombining motor patterns from various contexts (e.g., aggressive and sexual)constitutes a distinct and independent behavioral system (Burghardt, 2011;Pellis et al, 2019). While a certain level of cooperation is necessary for play to continue (Kraus et al, 2019), competition can also arise among players based on factors such as sex, age, species, and dominance relationship (Bauer & Smuts, 2007;Cordoni et al, 2021Cordoni et al, , 2023Palagi et al, 2016).…”

“…According to the Polyvagal Theory, play behavior serves as a form of neural exercise enhancing the efficiency of the neural circuit responsible for regulating the fight-or-flight response (Porges, 2009(Porges, , 2015. Although play, and especially play fighting, involves many behavioral patterns typical of the fight-or-flight response (Cordoni et al, 2023), it can be distinguished from "serious" aggressive or defensive behaviors by specific structural features, including pattern repetition and longer session duration (Cordoni et al, 2023). Play may also be regulated by social engagement which encompasses facial expressions, gestures, and vocalizations among interacting subjects (Porges, 2009(Porges, , 2015.…”

“…In particular, this can occur when the play session is highly competitive and the exchange of offensive (i.e., behavioral patterns aimed at attacking and pursuing the partner) and defensive (i.e., behavioral patterns aimed at eluding the attack and pursuit by the partner) patterns is markedly unbalanced between players (Cordoni et al, 2021(Cordoni et al, , 2023.…”