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

MERCEDES VALERA¹Ana Encina Martínez^1,2Sánchez-Guerrero M.J.¹Arantxa Rodríguez-Saínz de los Terreros²Ester Bartolome Medina^1*

• ¹Department of Agroforestry Sciences, Higher Technical School of Agricultural Engineering, University of Seville, Sevilla, Spain
• ²Real Asociación Nacional de Criadores de Caballos de Pura Raza Española (ANCCE),, Seville, Spain

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. A total of 98 male PRE horses, aged 4 to 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. 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 (r = 0.75, p<0.001), and learning and cooperation (r = 0.72, p<0.001). Eye temperature increased significantly just after competition, with higher values in horses with FHW along the eye line (p = 0.019). The number and location of FHW were associated with some interactions between nervousness, dominance, and/or aggression (p < 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.