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🐴 Vet-Approved Guide to Reading Equine Facial Expressions for Stress | 2025 Horse Behavior Insights 😟
By Dr Duncan Houston, BVSc
Horses speak volumes without saying a word. They communicate through movement, posture, and—most powerfully—their facial expressions. Until recently, interpreting those subtle cues was mostly guesswork. But new veterinary research has unlocked the science behind facial tension and its connection to stress and pain. 🧠🐎
In this 2025 guide, we explore the Horse Grimace Scale (HGS), how muscular tension reveals stress, and how you can use these insights to improve your horse’s emotional and physical well-being. 📸🐴
📚 What Is the Horse Grimace Scale?
The Horse Grimace Scale is a scientifically validated tool designed to measure pain and stress in horses based on six specific facial expressions. Each expression corresponds to muscular tension and subtle behavioral changes in the horse’s face. 🧾🧬
🧠 Developed To Detect Pain & Tension
Originally developed for veterinary research, the HGS allows caretakers, vets, and trainers to better understand how horses feel—even when they’re not showing obvious signs of illness or distress. 📊
Each expression is scored on a scale from 0 to 2:
- 0 = No tension or normal appearance
- 1 = Moderate tension
- 2 = High tension or abnormal expression
With a possible total score of 12, higher numbers indicate more pronounced facial tension, often linked to discomfort or emotional stress. 🧮🐴
🖼️ The 6 Facial Features on the Horse Grimace Scale
Each of these features provides insight into your horse’s internal state. Let’s explore them in detail:
- 🦻 Stiffly Backward Ears – While ears move constantly, persistently stiff and flat ears often suggest discomfort or irritability.
- 👁️ Tension Around the Eyes – Look for wrinkles above the eye, tightness around the eyelids, or a “hard” eye appearance.
- 💪 Strained Chewing Muscles – Known as the masseter muscles, visible clenching or bulging suggests jaw tension or stress.
- 👄 Tight Mouth – A clenched muzzle, puckered lips, or pinched mouth corners indicate unease.
- 😬 Pronounced Chin – A wrinkled or square-shaped chin area can point to stress-related muscle engagement.
- 👃 Strained Nostrils & Flat Profile – Flared nostrils and a compressed face profile often occur during physical or emotional strain.
Each change may seem subtle, but together they paint a detailed picture of how your horse is coping—physically and emotionally. 🖼️📖
🔬 The Science Behind Facial Tension in Horses
One key breakthrough came from equine researchers using surface electromyography (sEMG)—a method that tracks the electrical activity of muscles through skin-surface electrodes. 🧪⚡
By applying sEMG to the masseter (jaw) muscles, researchers observed significant muscle activation during stress-inducing situations. This objectively confirmed what the Grimace Scale indicates visually—stress literally registers in the face. 📉💥
Masseter Muscles: A Window into Equine Emotion
- 📍 Located on both sides of the jaw
- 💪 Control chewing, biting, and facial tension
- ⚠️ Show electrical changes under physical or emotional strain
This research empowers us to monitor horses’ emotional state using observable clues, especially when combined with a professional assessment or digital imagery. 🧠👁️
📷 Study Example: Horses in a PTSD Program
To evaluate the welfare of therapy horses, researchers applied the Horse Grimace Scale to horses involved in a veteran PTSD rehabilitation program. The concern was whether repeated emotional interaction might negatively affect the horses involved. 🪖🐴
Study Design:
- 🐎 8 geldings participated
- 👥 4 horses engaged in the program; 4 were used as control (not engaged)
- 📸 Facial photos were taken before, during, and after interactions
Results showed no significant increase in stress-related facial tension in therapy horses. In fact, many horses displayed neutral or relaxed facial expressions, even during interactions. This supports the growing belief that well-managed therapy programs can benefit both humans and horses. 💙🧘♂️🐎
👀 How to Use the Horse Grimace Scale at Home
Whether you're a trainer, caretaker, or owner, this scale can help you recognize signs of stress or pain early—before they become severe. 🧭
📝 Practical Steps:
- 📸 Take photos or video of your horse at rest (baseline)
- 👁️ Compare expressions during work, medical procedures, or social interactions
- 📋 Record and score each of the 6 HGS indicators
📊 Track Scores:
A single high score may indicate a fleeting reaction—but consistent or rising totals (6+) may signal ongoing discomfort or stress. 🆘
📱 Tools That Help: Use Ask A Vet for Behavioral Support
The Ask A Vet app allows you to:
- 📷 Upload close-up face images for vet review
- 📋 Log tension scores and track changes over time
- 🧠 Get tailored advice for medical vs behavioral stress
It’s an ideal tool for proactive care and wellness tracking in all equine disciplines. 🐴📲
🧘♀️ Helping Horses Relax: Reducing Facial Tension
If your horse consistently shows facial tension, investigate the possible causes and provide stress relief. 🧘♂️💆
🧠 Common Causes of Equine Stress:
- 🚚 Trailering or new environments
- 🏇 Intense or unfamiliar training
- 🔊 Loud sounds or chaotic barn setups
- 🩺 Illness, dental pain, or hoof soreness
🌿 Stress-Reducing Tips:
- 🧹 Maintain a predictable routine
- 🎵 Use calming sounds or quiet areas
- 🫶 Allow positive social interactions with other horses
- 🧴 Use massage, acupuncture, or calming supplements as advised by your vet
Be patient—emotional comfort is just as important as physical care. 🌸
✅ Quick Reference: The Horse Grimace Scale Checklist
- 🦻 Ears back or stiff
- 👁️ Tightened eyelids, wrinkles above eyes
- 💪 Bulging or strained jaw muscles
- 👄 Clenched or wrinkled lips
- 😬 Tense, pronounced chin
- 👃 Flared nostrils and flattened profile
Track these signs using the 0–2 scale. Consider a total score of 6+ worth further vet assessment. 🩺🧠
📲 Final Thoughts from Dr Duncan Houston
Understanding your horse’s emotions isn’t just heartwarming—it’s life-saving. Facial expressions are rich with meaning, and with tools like the Horse Grimace Scale, we can interpret stress early, respond wisely, and enhance our horses’ quality of life. 💙🐴
Use this knowledge to become your horse’s advocate—and always consult with a vet if something doesn’t look right. For ongoing support and image-based analysis, download the Ask A Vet app and connect with licensed equine professionals 24/7. 🐎📲
