Fine-scale collective movements reveal present, past and future dynamics of a multilevel society in Przewalski’s horses

Ozogány K, Kerekes V, Fülöp A, Barta Z, Nagy M 2023. Fine-scale collective movements reveal present, past and future dynamics of a multilevel society in Przewalski’s horses. Nature Communications 14: 5096. link

Abstract

Studying animal societies needs detailed observation of many individuals, but technological advances offer new opportunities in this field. Here, we present a state-of-the-art drone observation of a multilevel herd of Przewalski’s horses, consisting of harems (one-male, multifemale groups). We track, in high spatio-temporal resolution, the movements of 238 individually identified horses on drone videos, and combine movement analyses with demographic data from two decades of population monitoring. Analysis of collective movements reveals how the structure of the herd’s social network is related to kinship and familiarity of individuals. The network centrality of harems is related to their age and how long the harem stallions have kept harems previously. Harems of genetically related stallions are closer to each other in the network, and female exchange is more frequent between closer harems. High movement similarity of females from different harems predicts becoming harem mates in the future. Our results show that only a few minutes of fine-scale movement tracking combined with high throughput data driven analysis can reveal the structure of a society, reconstruct past group dynamics and predict future ones.

a Sample images and a sketch of the setup for 4k filming of Przewalski’s horses at Pentezug reserve, Hortobágy National Park, Hungary, in 2018 with two drones. The higher drone provides a large-scale top view for tracking individuals and the background to get coordinates and movement in an earth-fixed coordinate system (b). The lower drone scans the area with horses to get a detailed view for individual recognition. b Example trajectories of all horses belonging to the population (n = 278) from a 5-min long drone recording. Arrow shows the main direction of motion of the herd. Individuals (known identification, n = 238) are colour-coded based on the group they belong to (out of 31 harems), or shown as grey in the case of bachelor males (i.e., males that are not part of a harem, n = 40). c Detailed view of trajectories of a single harem, with all individuals shown with dots at a given point in time. Three letter codes show their identities. d Diagram of the main concept (on the left) showing important aspects of collectively living animals, and the complex interplays between these components. The components may have a relevant temporal scale (shown in the middle) that spans through several orders of magnitudes (from seconds and minutes to several decades). A detailed schematic explanation of each component is provided on the right.