Oxytocin homogenizes horse group organization

Area of Science:

• Behavioral Endocrinology
• Ethology
• Social Neuroscience

Background:

• The oxytocinergic system is implicated in the endocrine basis of group cohesion.
• Previous controlled studies on oxytocin's effects in open-group settings are lacking.

Purpose of the Study:

• To investigate the impact of exogenous intranasal oxytocin on group-level social organization in horses.
• To analyze changes in social structure using GPS tracking and social network analysis.

Main Methods:

• Utilized GPS tracking and social network analysis to monitor 58 horses (12 mares, 46 geldings) in 5 groups.
• Administered exogenous intranasal oxytocin to assess its effects on social interactions and organization.

Main Results:

• Oxytocin administration flattened social differentiation across all levels within the horse groups.
• Oxytocin selectively promoted homogenization by increasing associations between less-frequently interacting individuals/pairs.
• Conversely, high-baseline association pairs spent more time apart, leading to a more distributed network structure and lower clustering.

Conclusions:

• Exogenous oxytocin significantly alters social organization, shifting preferences toward homogenization.
• These findings extend the known role of oxytocin in collective behavior and social organization.
• The study highlights oxytocin's influence on the evolution of group-based sociality across species.