Dominance and Leadership in the Equine Social Structure: A Preliminary Study About Mules and Sex Influence.

The research paper investigates the social structure, dominance, and leadership behaviours of mules and horses, finding them to be similar but less stable in mules. Furthermore, it revealed a contrast in sex influence, with female mules demonstrating more aggression compared to males.

Study Design and Methodology

• The researchers compared the social behaviour of independently grouped mules and horses. Each group contained 11 animals.
• Over the course of four days, the frequency of threat, aggression, and leadership behaviours was documented through filming.
• The focus was primarily on aggressive and threat behaviours to determine dominance and social structure.

Findings from the Experiment

• Aggression was uncommon in both groups, and when observed was typically associated with threat behaviours.
• The research found a linear social structure in both groups. Within this structure, males ranked higher in dominance.
• Mules showed more specific types of aggressive behaviours, while horses demonstrated more specific types of threat behaviours.
• Despite mules displaying more agonistic social interactions without a clear submissive individual, this led to their social structure being deemed less stable than that of horses.

Sex Influence in Behavioral Differences

• When comparing genders, male mules displayed more leadership behaviours than male horses.
• Females in the horse group exhibited more leadership traits than female mules.
• In terms of within-group behaviour, in the mule group, males showed more leader and threat behaviours than females, whose behaviours leaned more towards aggression.
• However, in the horse group, female horses showed more leadership behaviours than male horses. Both genders showed similar frequencies of threat behaviours.

Conclusion

• The research concluded that mule social structure is similarly linear to that of horses, but less stable due to increased aggression and lack of clear submissive roles.
• In contrast to horses, mules did not show a gender influence in leadership. However, they did show a gender effect in aggression, with females displaying more aggressive behaviours than males.