Personality predicts collective behavior in greylag geese: Influencers are bold and followers are exploratory

Abstract

Simple interaction rules describe the coordination of individual behavior into collective behavior. However, we lack long-term tests of individually tagged individuals in the wild to understand fitness payoffs of different social roles during collective movement. Here, we interrogate leader-follower roles in greylag geese (Anser anser) in relation to personality traits (boldness, aggressiveness, and exploration). We calculated an influencer score based on the number of followers for sub-group movement events across four years. Influencer score was weakly but significantly repeatable over time, and all three personality traits were repeatable. Greylag geese with higher influencer scores were bolder, and geese that were first to follow a non-partner influencer goose were more exploratory and more likely to look behind the mirror during a mirror stimulation test. In light of these findings, we discuss potential individual-level benefits of following a bold individual and the presumed group-level benefits of new information spread via followers open to novelty.

Keywords: Ornithology; Psychology; Social sciences; Wildlife behavior; Zoology.

Graphical abstract

Figure 1

Association between an individual’s boldness and influencer score Best linear unbiased predictors (BLUPs) from a bivariate linear mixed model showing the among-individual correlation between an individual’s boldness (flight initiation distance) and influencer score (departure group size). Bolder individuals (shorter flight initiation distance) recruited a larger group size following their departure calls. See also Table S1.

Figure 2

Personality traits and influencer group size in greylag geese Estimated correlations (mean ± 95% CrI) between focal individuals’ departure group size after departure calling and four behavioral traits: boldness (flight initiation distance during human approach assays), aggressiveness (response to a mirror stimulation test), neophobia (response to a novel object test), and mirror inspection (looked behind the mirror during a mirror stimulation test). Credible intervals do not overlap zero for boldness, indicating that bolder geese (i.e., with shorter flight initiation distances) recruited more followers. See also Table S1.

Figure 3

Personality traits associated with first-follower behavior in greylag geese Estimated correlations (mean ± 95% CrI) between an individual’s first-follower count (the number of times it was first to follow a departing goose) and three personality traits: (A) boldness (flight initiation distance during a human approach assay), (B) aggressiveness (response to a mirror stimulation test), and (C) neophobia (response to a novel object test). Credible intervals do not overlap zero for neophobia, indicating that less neophobic geese (i.e., with shorter latency from 2 m to 1 m to approach a novel object) were more likely to be the first to follow a non-partner departing goose. See also Table S2.

Figure 4

Mirror inspection behavior and first-follower frequency in greylag geese The relationship between mirror inspection behavior (whether or not a goose looked behind the mirror during the mirror stimulation test) and the number of times a goose was recorded as being the first to follow throughout the study period (2020–2023, n = 51 individuals). Error bars represent 95% CIs around the estimated marginal mean. See also Table S3.