Testing for personality consistency across naturally occurring behavioral contexts in sanctuary chimpanzees (Pan troglodytes)

Abstract

Personality is both a reflection of the bio‐behavioral profile of individuals and a summary of how they typically interact with their physical and social world. Personality is usually defined as having distinct behavioral characteristics, which are assumed to be consistent over time and across contexts. Like other mammals, primates have individual differences in personality. Although temporal consistency is sometimes measured in primates, and contextual consistency is sometimes measured across experimental contexts, it is rare to measure both in the same individuals and outside of experimental settings. Here, we aim to measure both temporal and contextual consistency in chimpanzees, assessing their personality with behavioral observations from naturally occurring contexts (i.e., real‐life settings). We measured personality‐based behaviors in 22 sanctuary chimpanzees, in the contexts of feeding, affiliation, resting, and solitude, across two time periods, spanning 4 years. Of the 22 behaviors recorded, about 64% were consistent across two to four contexts and 50% were consistent over time. Ten behaviors loaded significantly onto three trait components: explorativeness, boldness‐sociability, and anxiety‐sociability, as revealed by factor analysis. Like others, we documented individual differences in the personality of chimpanzees based on reliably measured observations in real‐life contexts. Furthermore, we demonstrated relatively strong, but not absolute, temporal, and contextual consistency in personality‐based behaviors. We also found another aspect of individual differences in personality, specifically, the extent to which individual chimpanzees show consistency. Some individuals showed contextual and temporal consistency, whereas others show significant variation across behaviors, contexts, and/or time. We speculate that the relative degree of consistency in personality may vary within chimpanzees. It may be that different primate species vary in the extent to which individuals show consistency of personality traits. Our behavioral‐based assessment can be used with wild populations, increasing the validity of personality studies, facilitating comparative studies and potentially being applicable to conservation efforts.

Object use in communication of semi-wild chimpanzees

“…The behavioural context referred to the situational circumstances during which the onset of the object action was observed. Seven mutually exclusive categories were used: social play, solitary play, allogrooming, autogrooming, feeding, resting, and agnostic and (see Table 3 for definitions) (Chotard et al 2023 ; Liebal et al 2006 ; Pika et al 2005 ). In cases where the context of the object action changed mid event (e.g., prolonged touching), we coded the initial context during which the object action was instigated.…”