Origin and experience influence the leading behaviour of reintroduced Przewalski's horses

Analysing social behaviour provides valuable insights into the dynamics of species living in groups. An essential part of social behaviour is represented by lead-and-follow interactions as they influence group stability through individual needs and decision making. In horses, Equus ferus caballus, this behaviour plays a crucial role since individuals depend on the security and knowledge their group offers. Only one study has analysed the lead-and-follow behaviour of Przewalski's horses, Equus ferus przewalskii. However, no such study has been conducted on the wild population, nor on the potential impact of the horses' origin and experience. We filmed 34 wild-born and captive-bred individuals with different experiences (held in a fenced enclosure before release into the wild, long-term reintroduced and wild-born) in the Great Gobi B (Mongolia) over summer 2018, late spring 2019 and autumn 2019 to investigate Przewalski's horses' lead-and-follow behaviour in situ. We documented lead-and-follow interactions within 11 groups and used these data to construct lead-and-follow networks. We also examined the influence of various social factors (origin, sex, age, dominance rank, group size, parity, kinship and time belonging to the group) on different network measures. The analyses revealed that wild-born horses with greater experience in the area tended to exhibit well-defined lead-and-follow connections with few leading individuals, typical of stable groups of horses. In contrast, in inexperienced reintroduced groups, many (or all) members controlled the movement. The results show that newly formed groups of released Przewalski's horses require time to develop typical and stable lead-and-follow patterns.