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iScience2024; 27(7); 110356; doi: 10.1016/j.isci.2024.110356

Oxytocin homogenizes horse group organization.

Abstract: The oxytocinergic system has been suggested to make up an important part of the endocrine basis of group cohesion. However, controlled studies in open-group settings have not been performed. We here investigated the impact of exogenous intranasal oxytocin on the group-level social organization of 5 groups of horses ( = 58; 12 mares and 46 geldings) through GPS tracking and social network analysis. We find oxytocin flattened social differentiation across levels. Most strikingly, oxytocin did not simply reinforce existing bonds but selectively shifted social preferences toward homogenization - individuals and pairs who otherwise rarely associated spent more time close together, while individuals and pairs with the highest baseline association instead spent more time further apart. This resulted in a more distributed structure and lower clustering coefficient at the network level. These effects reinforce and extend oxytocin's role in collective behavior, social organization, and the evolution of group-based sociality across taxa.
© 2024 The Author(s).
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Publication Date: 2024-06-24 PubMed ID: 39071893PubMed Central: PMC11277748DOI: 10.1016/j.isci.2024.110356Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research investigates how the hormone oxytocin impacts the social organization of horse groups, finding it encourages a more evenly distributed social structure.

Objective of the Study

The researchers in this study aim to understand how the hormone oxytocin, which is often connected with social bonding and cohesion, influences the group-level social organization of horses. They conducted the study with 5 groups of horses (total 58 horses: 12 mares and 46 geldings).

Methodology

  • The researchers administered exogenous intranasal oxytocin, an artificially-created version of the hormone, to the horses.
  • They used GPS tracking devices and social network analysis to study the impact of the hormone on the horses’ movement and social interactions.

Findings

  • The study found that oxytocin reduced differences across social levels. This means that interactions among the horses became more evenly distributed following the introduction of oxytocin.
  • The hormone also altered existing social preferences among the horses. Instead of strengthening existing bonds, oxytocin led horses who rarely interacted to spend more time together. Conversely, horses who often associated with each other spent more time apart after oxytocin was introduced.
  • Overall, the hormone led to a more distributed social structure among the horses and reduced clustering at the network level.

Significance of the Study

This investigation’s findings lend empirical support to the idea that oxytocin plays a crucial part in group cohesion and social organization among species. The researchers posit that this study contributes to our understanding of oxytocin’s role in collective behavior, social organization, as well as the evolution of group-based sociality across different species (taxa).

Cite This Article

APA
Brooks J, Maeda T, Ringhofer M, Yamamoto S. (2024). Oxytocin homogenizes horse group organization. iScience, 27(7), 110356. https://doi.org/10.1016/j.isci.2024.110356

Publication

iScience
ISSN: 2589-0042
NlmUniqueID: 101724038
Country: United States
Language: English
Volume: 27
Issue: 7
Pages: 110356
PII: 110356

Researcher Affiliations

Brooks, James
  • Institute for Advanced Study, Kyoto University, Kyoto, Japan.
  • Wildlife Research Center, Kyoto University, Kyoto, Japan.
Maeda, Tamao
  • Wildlife Research Center, Kyoto University, Kyoto, Japan.
  • Research Center for Integrative Evolutionary Science, The Graduate University of Advanced Science (SOKENDAI), Hayama, Japan.
Ringhofer, Monamie
  • Department of Animal Sciences, Teikyo University of Science, Tokyo, Japan.
Yamamoto, Shinya
  • Institute for Advanced Study, Kyoto University, Kyoto, Japan.
  • Wildlife Research Center, Kyoto University, Kyoto, Japan.

Conflict of Interest Statement

All authors declare no competing interests.

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Citations

This article has been cited 1 times.
  1. Cheng L, Samuni L, Deschner T, Surbeck M. Oxytocin activity is not linked to out-group prosociality in wild bonobos. Sci Rep 2025 Jun 3;15(1):19408.
    doi: 10.1038/s41598-025-00209-wpubmed: 40461471google scholar: lookup
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