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Frontiers in veterinary science2026; 13; 1709706; doi: 10.3389/fvets.2026.1709706

Facial hair whorl location, behavior, and ocular temperature as a physiological stress indicator in young Pura Raza Española dressage horses.

Abstract: Behavioral and emotional reactivity assessment in sport horses is essential for optimizing their management and sports performance, particularly in equestrian disciplines such as Dressage. This study investigates, in Pura Raza Española (PRE) horses, the association between facial hair whorl (FHW) patterns, behavioral traits, and physiological stress responses using ocular temperature (OT) assessed with infrared thermography as, an objective, non-invasive physiological stress indicator. Unassigned: A total of 98 male PRE horses, aged 4-6 years old and all gray coated, were evaluated during the 2022-2024 Young Horse Selection Tests for Dressage. The FHW that were present on these PRE horses were classified by number and location (above, along, or below the eye line), while OT was recorded at rest, immediately post-competition, and several hours post-competition. Seven behavioral traits assessed via a standardized rider survey were also analyzed. Behavioral traits were assessed during the competition period through a standardized questionnaire completed by the regular rider, reflecting the horse's general behavioral profile rather than responses to a single test. Unassigned: Most horses presented a single FHW, predominantly along the eye line (60.2%). Behaviorally, a balanced profile was common, with strong correlations observed between aggression and dominance ( = 0.75, < 0.001), and learning and cooperation ( = 0.72, < 0.001). Eye temperature increased significantly just after competition, with higher values in horses with FHW along the eye line ( = 0.019). The number and location of FHW were associated with some interactions between nervousness, dominance, and/or aggression ( < 0.05). Multivariate analyses identified three distinct clusters, with the most favorable group characterized by FHW below the eye line, lower post-test temperatures, and high learning and cooperation scores. These findings demonstrate that, although FHW alone are not sufficient to predict temperament or stress reactivity, their integration with behavioral and physiological measures allows the empirical identification of distinct functional profiles in PRE horses.
Copyright © 2026 Valera, Encina, Sánchez-Guerrero, Rodríguez-Sainz de los Terreros and Bartolomé.
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Publication Date: 2026-02-19 PubMed ID: 41800313PubMed Central: PMC12960158DOI: 10.3389/fvets.2026.1709706Google Scholar: Lookup
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Summary

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Overview

  • This study explores how facial hair whorl (FHW) patterns, behaviors, and physiological stress (measured by eye temperature) relate in young Pura Raza Española dressage horses to better understand their temperament and stress responses during competition.

Background and Purpose

  • Assessing behavioral and emotional reactivity is important for managing sport horses and improving performance, especially in dressage.
  • The researchers focused on Pura Raza Española (PRE) horses, a breed used in dressage, to see if patterns in facial hair whorls, which are natural hair growth patterns, relate to behavior and physiological stress.
  • Ocular temperature (OT) measured by infrared thermography was used as a non-invasive method to track physiological stress response.

Study Subjects and Methods

  • The study included 98 male PRE horses aged 4-6 years, all gray-coated.
  • These horses were assessed during the 2022-2024 Young Horse Selection Tests for Dressage.
  • Facial hair whorls were classified by:
    • Number present (mostly one per horse)
    • Location relative to the eye line: above, along, or below it
  • Ocular temperature was recorded at three time points:
    • At rest
    • Immediately after competition
    • Several hours post-competition
  • Behavioral traits were assessed through a standardized questionnaire completed by the horse’s regular rider, capturing general temperament during competitions rather than isolated reactions.
  • Seven behavioral traits evaluated included aggression, dominance, learning, cooperation, nervousness, and others.

Key Findings: Facial Hair Whorl Patterns

  • Most horses had a single hair whorl (60.2%) located along the eye line.

Behavioral Correlations

  • Strong positive correlation between aggression and dominance (correlation coefficient = 0.75, highly significant).
  • Strong positive correlation between learning and cooperation traits (correlation coefficient = 0.72, highly significant).
  • Some behavioral traits such as nervousness, dominance, and aggression had significant associations with the number and location of FHWs.

Physiological Stress Response (Ocular Temperature)

  • Eye temperature significantly increased immediately after competition compared to rest.
  • Horses with FHW along the eye line showed higher post-competition ocular temperatures (p = 0.019), indicating a possible greater stress response.
  • Temperature levels several hours after competition were not specified but implied to return closer to baseline.

Multivariate Analysis and Group Clustering

  • Complex statistical methods grouped horses into three distinct clusters based on FHW location, behavioral traits, and ocular temperature.
  • The most favorable cluster included horses with:
    • FHW below the eye line
    • Lower eye temperatures post-test (indicating lower stress)
    • High scores for learning and cooperation

Conclusions and Implications

  • Facial hair whorl characteristics alone do not fully predict a horse’s temperament or stress reactivity.
  • Combining FHW analysis with behavioral assessments and physiological stress markers like ocular temperature offers a more empirical way to identify functional temperament profiles in PRE dressage horses.
  • This integrated approach could help optimize horse management, training, and performance evaluation in dressage.

Cite This Article

APA
Valera M, Encina A, Sánchez-Guerrero MJ, Rodríguez-Sainz de Los Terreros A, Bartolomé E. (2026). Facial hair whorl location, behavior, and ocular temperature as a physiological stress indicator in young Pura Raza Española dressage horses. Front Vet Sci, 13, 1709706. https://doi.org/10.3389/fvets.2026.1709706

Publication

Frontiers in veterinary science
ISSN: 2297-1769
NlmUniqueID: 101666658
Country: Switzerland
Language: English
Volume: 13
Pages: 1709706
PII: 1709706

Researcher Affiliations

Valera, Mercedes
  • Dpto. Agronomía, Área de Producción Animal, Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Seville, Spain.
Encina, Ana
  • Dpto. Agronomía, Área de Producción Animal, Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Seville, Spain.
  • Real Asociación Nacional de Criadores de Caballos de Pura Raza Española (ANCCE), Seville, Spain.
Sánchez-Guerrero, María José
  • Dpto. Agronomía, Área de Producción Animal, Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Seville, Spain.
Rodríguez-Sainz de Los Terreros, Arantxa
  • Real Asociación Nacional de Criadores de Caballos de Pura Raza Española (ANCCE), Seville, Spain.
Bartolomé, Ester
  • Dpto. Agronomía, Área de Producción Animal, Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Seville, Spain.

Conflict of Interest Statement

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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