Do domestic horses (Equus caballus) show a visual preference for the same-age conspecifics?

An experimental study focused on the similarity principle

Abstract

Social animals have enduring affiliative relationships (i.e., social bonds) with conspecifics. It has been reported that individuals who have strong social bonds are adaptive in terms of reproduction (e.g., Cameron, Setsaas & Linklater, 2009). Moreover, the similarity principle suggests that individuals may choose a similar group member as a partner of the affiliative interaction and start to form social bonds with him/her (de Waal & Luttrell, 1986). In fact, domestic horses (Equus caballus) build more strong social bonds with their more similar age group members (Wilds, 2019). However, it is still unclear whether horses prefer the similar age conspecifics before interacting with them. In this study, we investigated whether domestic horses show a visual preference for the same-age conspecifics by using photos of stranger horses (old age, same-age or young age) in single presentations. The participant horses’ gaze, approach, and touch behaviors toward the photos did not change regardless of the stranger horse’s age. These results suggest that domestic horses do not show a visual preference for the same-age conspecifics without any interactions with them.