A novel methodological approach for group classification during fission of a semi‐free‐ranging group of Japanese macaques (Macaca fuscata)

Abstract

The self‐initiated split of a social group, known as fission, is a challenge faced by many group‐living animals. The study of group fission and the social restructuring process in real time provides insights into the mechanism of this biologically important process. Previous studies on fission in Japanese macaques (Macaca fuscata) assigned individuals to newly reorganized groups mainly using behavioral observations and group attendance records based on periods before or after fission itself. Here, we present a novel framework for group classification during the process of fission that uses quantifiable behavioral variables and statistical analyses. The framework was tested on a group fission process at Affenberg Landskron (Austria), a park that housed around 160 semi‐free‐ranging Japanese macaques. The behavioral data were collected for 26 days during fission. We analyzed three behavioral developments recurrent in fissions in Japanese macaques, that is, independence of behavior, participation in group movements, and separation of nomadic ranges. These analyses were combined to assign individuals to different groups. Our study resulted in one main group (N = 33), one subgroup (N = 36) and 56 individuals whose group membership was still undefined. The demographic characteristics of these newly formed groups were comparable with those of fissioned groups in wild populations. Furthermore, we found that these newly forming groups showed early social dynamics of fission five months before group level movements, that is: grouping based on spatial proximity and spatial withdrawal of the subgroup to the periphery. These results underline the validity of our novel framework to study social dynamics in Japanese macaques during the process of fission. It represents an important addition to existing methods, and we recommend testing its scope in other primate societies.

Prosociality in a Despotic Society

“…Finally, prosociality has been argued to be the foundation for inter-group conflict 80 ; consequently, ingroup prosociality and parochial cooperation can be favored. Our study group recently underwent fission, forming two distinct subgroups, 81 and all participating individuals in the current study belonged to one of the subgroups. Therefore, it would be interesting to test in future studies whether such an ecological event of fission may have governed the prosocial motivations we witnessed in our study.…”

“…The macaques were present in an enclosure of 40,000 m 2 with a natural mixed forest common to southern Austria 49 (see Figure S4). At the time of testing, approximately 74% and 19% of the individuals were >3 and %3 but R1 year old, respectively (see 81 for details). The study group was habituated to the presence of human experimenters but with limited human intervention, except for feeding and emergency medical purposes (such as veterinary care).…”

Prosociality in a despotic society

“…Finally, prosociality has been argued to be the foundation for inter-group conflict 80 ; consequently, in-group prosociality and parochial cooperation can be favored. Our study group recently underwent fission, forming two distinct subgroups, 81 and all participating individuals in the current study belonged to one of the subgroups. Therefore, it would be interesting to test in future studies whether such an ecological event of fission may have governed the prosocial motivations we witnessed in our study.…”

“…The macaques were present in an enclosure of 40,000 m 2 with a natural mixed forest common to southern Austria 49 (see Figure S4 ). At the time of testing, approximately 74% and 19% of the individuals were >3 and ≤3 but ≥1 year old, respectively (see 81 for details). The study group was habituated to the presence of human experimenters but with limited human intervention, except for feeding and emergency medical purposes (such as veterinary care).…”