Stress is something we all feel, whether it is about an upcoming meeting or a deadline, and our horses experience it too. The word stress covers a lot of different aspects of our response to our environment with the main split being between internal (e.g. having an empty stomach and feeling hungry) and external, which is what I will be focusing on here.
Another way of describing objects or situations that cause stress is an ‘acute stressor’, these stresses are brief but can sometimes cause explosive responses, which often reduce rapidly when the stressor is removed. These responses are often referred to as freeze-flight-fight. Some specific initial reactions to stress that are measured when scientists investigate this are:
Increased heart rate and breathing rate
Decreased or halted digestion
Dilation of the pupils
Tensing of muscles
Horses, as they are prey animals that naturally live in large open plains, are predisposed to flight. Anyone who has worked with horses knows that their horse will be off in a flash the minute they get spooked. However if they don’t have enough space, or are forced to stay still, they can quickly adjust their response to fight. Fight is defensive and often a last resort for horses, but if a horse has experienced the same stressor before and knows they cannot escape they are more likely to fight first.
Example: A horse who is needle shy may try to run first before trying to bite the handler/vet. The next time the vet comes they may try to bite or kick them straight away.
In general horses don’t go into freeze in the same manner as other species such as rabbits or deer as they are, as stated above, much more likely to flee. However horses do often pause and stand still before going into flight-fight which is an important behaviour to notice to avoid possible explosive responses later. Their flight response can obviously cause injury if they run over us, however the horse is at their most dangerous during fight responses. These behaviours include rearing, biting, kicking, and other defensive and aggressive motions. So how do we reduce our risk of injury when dealing with horses in stressful situations? I can easily say that preparation is key, that making sure the horse is relaxed and calm and knows what is going to happen to them without pressure beforehand reduces risk of injury when the procedure actually occurs (The “Don’t break your vet” video series is a perfect demonstrator of this). But we cannot always pre-prepare our horses, injury can disrupt plans and horses can be relaxed around one vet but not another. So what then?
The best way to reduce injury risk is to prevent the horse going into freeze-flight-fight by recognising the signs of stress early when they are more subtle. When we notice the subtle signs we can remove or reduce the impact of the stressor by reducing intensity or increasing distance between the object and the horse, giving the horse space to relax again. Recognising stress is difficult, I won’t lie and it takes a very long time to become accurate, but some of the least ambiguous signs and a few that are not as obvious but just as important are listed below. To briefly clarify, pain is an internal stressor but as it causes stress the signs are the same for pain and external stressors for some behaviours.
The face:
The horse grimace scale (HGS) was designed by Dalla-Costa and co and is pictured below and Gleerup and co designed the equine pain face which is further below.
Source: Dalla Costa et al (2014)
Source: (a) pain free horse (b) asymmetrical ears pain face, (c)ears back pain face (Gleerup et al., 2014)
The body:
Stereotypical behaviours (colloquially known as vices such as: weaving, box walking, head bobbing/nodding, fence walking/pacing)
Scratching repeatedly at the stable walls
Pawing the ground with front feet
Stamping with back feet
Barging
Tension
Fidgeting
Jumping or startling easily
Defecating (often a small amount and/or high frequency)
The tail:
Repeatedly swishing
Held stiffly to the side or away (more common with pain)
Raised up
Clamped down
If you recognise a few of these behaviours during a stressful moment it is important to stop what you are doing. If the horse begins to relax and stops the previous behaviour then you can continue at a slower pace, however if they don’t begin to relax it is important to reduce the stressor’s impact by moving it away from the horse or reducing the intensity.
Example: the horse starts to snort and raise their head when you bring the clippers over so you stop moving them closer and turn them off, the horse does not change their snorting or raised head so you move the clippers away and the horse lowers their head and begins to breathe more steadily.
But sometimes everything doesn’t go to plan, you may have trained and trained and reduced that fear, stopped them responding to it using positive methods, they may have been relaxed and calm for months of the stressor occuring, but then one day boom! they suddenly spook at it. Maybe there’s a chair that has always sat in that corner of the arena and your horse has had no problem going past it, but one day you try to pick up canter there and they buck and bolt off. Often this is because the horse was at threshold when they went past it this time around, and moving past the object was enough to tip them over threshold. Threshold is a term used to describe the amount of stress an individual can cope with before going into freeze-flight-fight. Sometimes this term has been demonstrated with a bucket metaphor such as the one pictured below. Everything that happens in a day has a volume of water attached to it that adds to the bucket (this volume will be different for every horse), and while the water stays below the rim of the bucket the horse can stay calm and relaxed (relaxation is often called rest and digest as your digestion stops when you are stressed). But when the water tips over the edge of the bucket and starts to pour out then we get our freeze-flight-fight response, and when the subtle signs have not been noticed, the reaction may seem to come ‘out of nowhere’.
Source: The Charity of Civil Servants
Horses’ stress responses have the potential to be dangerous or life threatening, but only when we don’t prepare them or listen to their more subtle signs. Every day our horses tell us how they feel, and the more times we pay attention to those smaller signs, the less the need to become louder. The more we listen and respond, the less danger we are in.
This post detailed acute stress, how to recognise it and appropriately respond in a general manner. I will discuss specific stress responses, video demonstrations etc. in the coming months, and have a post planned about acute stress’s less obvious cousin, chronic stress. If you want, some of the references I used to create this post are below. And a tip from someone in higher education: if you can’t access the paper, search for it in google scholar to see if there is an open access version or research gate as they sometimes have free PDF’s of the papers, and don’t hesitate to contact the lead author of the paper as they are often happy to send you the paper to read.
References
Dalla Costa. A, Minero. M, Lebelt. D, Stucke. D, Canali. E, and Leach. M.C, (2014) Development of the Horse Grimace Scale (HGS) as a Pain Assessment Tool in Horses Undergoing Routine Castration PLoS ONE 9(3) pp. e92281 DOI: https://doi.org/10.1371/journal.pone.0092281
Gleerup. K.B, Forkman. B, Lindegaard. C, and Andersen. P.H, (2014) An equine pain face Veterinary Anaesthesia and Analgesia 43(1) pp. 103-114 DOI: https://doi.org/10.1111/vaa.12212
Harrison. J, (2018) Watch Out for These Four Signs of Stress in Your Horse Available at: https://www.yourhorse.co.uk/horse-care/horse-behaviour/watch-out-for-these-four-signs-of-stress-in-your-horse/?rq=justine%20harrison [Accessed 26/01/22]
Harrison. J, (2021) Spot signs of anxiety in your horse using the traffic light system and improve your bond [Online] Available at: https://www.yourhorse.co.uk/horse-care/horse-behaviour/spotting-the-signs-of-anxiety-in-your-horse-the-traffic-light-system/?rq=Justine%20harrison [Accessed 26/01/22]
McGreevy. P.D, and McLean. A, (2005) Behavioural problems with the ridden horse in Mills. D, and McDonnell. S The domestic horse: The origins, development and management of its behaviour Cambridge: Cambridge University Press pp.196-211.
Young. T, Creighton. E, Smith. T, and Hosie. C, (2012) A novel scale of behavioural indicators of stress for use with domestic horses Applied Animal Behaviour Science140(1-2) pp. 33-43 DOI: https://doi.org/10.1016/j.applanim.2012.05.008
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