Dominance and Leadership in the Equine Social Structure: A Preliminary Study About Mules and Sex Influence.
Authors: Narciso Matheus H P M, da Luz Marina P F, Maia Caroline M, Filho José Nicolau P P
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Whilst equine social hierarchies have been extensively documented in horses, little research exists on dominance structures in mules—a gap this preliminary study addressed by directly comparing agonistic behaviours in matched groups of 11 mules and 11 horses observed over four consecutive days. The researchers quantified threat and aggressive interactions to map social rank and leadership patterns, paying particular attention to sex-based differences in behavioural expression. Although both species maintained broadly linear dominance hierarchies weighted towards males, mules displayed a notably less stable social structure characterised by more frequent aggression and agonistic interactions without clear submission, alongside a distinct absence of the sex-linked leadership differences seen in horses. Interestingly, whilst male mules exhibited greater leadership and threat behaviours than females, female mules paradoxically showed significantly higher aggression rates—a pattern inverse to horses, where mares demonstrated more leadership behaviour than stallions. For practitioners managing mixed herds or assessing temperament in mules, these findings suggest that female mules may require closer monitoring during introductions or grouping, and that reliance on conventional equine social-reading strategies may prove insufficient, given mules' apparently more volatile and less readily predictable hierarchy establishment.
Read the full abstract on PubMed
Practical Takeaways
- •Mules show distinctly different social dynamics than horses with less predictable hierarchies—expect more frequent agonistic interactions and plan group management accordingly
- •Sex influences social structure differently in mules versus horses; female mules are more aggressive while female horses are more leadership-oriented, requiring sex-specific handling strategies
- •Mule group stability may require closer monitoring and management intervention compared to horses due to less consistent dominance patterns and increased aggression
Key Findings
- •Mule social structure was less stable than horses, involving more aggression and agonistic interactions without recognized submissive individuals
- •Male mules and horses ranked higher in dominance based on threat frequency, establishing linear social hierarchies
- •Female mules exhibited more frequent aggression than male mules, whereas female horses showed more leader behaviors than males
- •Mares demonstrated more leader behaviors than female mules, while male horses showed fewer leader behaviors compared to male mules