# Consistent Individual Differences Drive Collective Movements in a Tibetan Macaque Group

## TL;DR

Tibetan macaques show personality traits like sociability and boldness that influence their roles in group movements, with higher-ranking or less anxious individuals leading more effectively.

## Contribution

The study identifies three personality types in Tibetan macaques and demonstrates how these traits influence leadership and follower behavior during collective movements.

## Key findings

- Macaques with higher sociability, rank, or lower anxiousness are more likely to initiate successful collective movements.
- Higher-rank individuals and those with lower anxiousness attract more followers during group movements.
- Older individuals are less successful in initiating movements compared to young adults.

## Abstract

Do nonhuman primates, such as Tibetan macaques, exhibit personalities that influence their collective movements? In this study, we not only confirmed the presence of three personality types in Tibetan macaques but also found that individuals with higher sociability scores, higher rank, or lower anxiousness scores were more likely to initiate successful collective movement. We found that macaques with lower anxiousness scores or higher rank attracted more followers, and that higher-rank individuals tended to join movements earlier. Moreover, individuals with higher sociability and boldness scores exhibited shorter joining latency in group movements. These findings provide valuable insights into how personality influences collective movement in nonhuman primates.

Collective movement has emerged as a key area of interest in animal behavior. While individual differences are often viewed as a potential threat to group cohesion, growing evidence suggests that these differences can actually influence an animal’s behavior as an initiator or follower during collective movements, thereby driving the group‘s movement and decision-making processes. To resolve the divergence, we asked how personality can affect the dynamics of collective movements in one group of free-ranging Tibetan macaques (Macaca thibetana) in Huangshan, China. We assessed individual personality using principal component analysis and applied the generalized linear mixed model and linear mixed model to examine the influence of personality on decision making during collective movements. Our findings reveled three distinct personality types among Tibetan macaques: sociability, boldness, and anxiousness. Individuals with higher sociability scores and rank, or those with lower anxiousness scores, were more likely to initiate successful collective movements. Older individuals were less successful in initiating movements compared to young adults. Leaders with lower anxiousness scores or higher rank attracted more followers, with females attracting larger groups than males. As for followers, individuals with higher rank tended to join the collective movement earlier. Additionally, individuals with higher sociability or boldness scores had shorter joining latency in collective movement. Finally, there was a longer joining latency for middle-aged adults compared to young adults. These results suggest that individual differences are a potential driver of collective movements. We provide some insights into the relationships between personality and decision making in Tibetan macaques.