The diverse cultural repertoire of Balinese long-tailed macaques and its implications for primate welfare and conservation

Over the past two decades, field primatologists have reported numerous behavioral traditions (or cultures) in various primate taxa. For a behavior to qualify as cultural, it should be: (1) geographically variable (e.g., a group-specific behavioral practice), (2) prevalent (i.e., present among several group members), (3) persistent over time, and (4) dependent on social means for its diffusion, expression, maintenance, and possible transformation. Our first goal is to use these four criteria to provide an overview of the diversity in the cultural repertoire of Balinese long-tailed macaques (Macaca fascicularis fascicularis). Over the past 15 years conducting field research in Bali, we have compiled behavioral data from five populations of this primate species. Focusing on material culture, (candidate) behavioral traditions straddle across the following behavioral domains: object play (e.g., stone handling, “bottle game”), foraging-related tool use (e.g., object-assisted water-scooping), sex-related tool use (e.g., object-aided genital stimulation), social tool use (e.g., object-assisted eye-covering), and symbolic tool use (i.e., token-mediated bartering). Our second goal is to highlight the implications of cultural primatology for the welfare and conservation of primate populations. Previous research showed that animal culture can be an index of behavioral, socio-demographic, and genetic diversity, flexibility, and adaptability; it is also a metric of population welfare and environmental viability. We argue that this is particularly true for questionably adaptive cultural behaviors, such as object play and comfort-related tool use, whose fundamental characteristics (i.e., hedonism, autotelism, quirkiness, redundancy, arbitrariness, and latent potential) may contribute to assessing individual health, populational evolvability, and species-level conservation status.