This is called “fly bucking” by behaviorists.

Much like the broncos at a rodeo, bucking in horses is fairly obvious to spot—quick, sharp movements designed to dislodge any animal—including humans—from their backs. Bucking can involve an upward leap, usually with forward propulsion and either both hind limbs or even all four limbs off the ground. Horses might manifest other forms of bucking such as pronking, bronking and fly bucking. Pronking, or crow-hopping, describes horses that flex the thoracolumbar lumbar spine and leap upward with no forward movement. Alternatively, bronking is a violent manifestation of pronking in which the horse propels itself at high speed with an arched back and low neck. At those speeds, a sudden stop or change in direction will certainly dislodge the rider. This is the most dangerous form of bucking. Finally, when the horse leaps upward with the head high, forelimbs on the ground and back extended, one describes the movement as fly bucking.

While bucking is encouraged in rodeo horses, the behavior is undesirable in sport and leisure horses, sometimes making them unsafe to ride. Due to the inherent risks to the rider, bucking must not be ignored or anthropomorphized (applying human emotions to your horse’s behavior).

Conducting a careful clinical examination is the only way to identify the most likely underlying cause of bucking. Treatment might be medical or behavioral (training), but in some cases retirement or even euthanasia might be the only options.

Sue Dyson, MA, VetMB, PhD, DECVSMR, FRCVS, hails from The Cottage in the United Kingdom. Dyson is an expert in essentially all things horse. In addition to being an expert rider herself, Dyson publishes and lectures extensively on lameness, lameness diagnostics, as well as equine behavior, usually related to pain. She spoke about a paper she co-authored with Katy Thomson titled, “The recognition of pain and learned behaviour in horses which buck.” You can watch her presentation from the Equine Veterinary Education Video Abstracts series here. 

According to Dyson, bucking has five main causes:

1. Instinct

“Bucking is an instinctive defense mechanism against predators that attack their prey by leaping onto their backs. They are hardwired to instantaneously escape and subsequently avoid similar situations,” explained Dyson.

Domesticated horses are therefore trained to “ignore” their natural instinct to buck when a rider is on their back but could be triggered into bucking in certain instances.

2. Excitement

An excited, happy horse might buck. The problem is that even though there is no malice involved, the behavior is unpredictable and inconsistent, placing the rider at risk of injury.

3. Pain

Bucking can also result from physical discomfort usually due to musculoskeletal pain. Bucking occurs more frequently under saddle rather than when being lunged and more frequently at the canter than trot. Bucking and kicking out in jumpers often occurs after landing.

The main differentials for pain-related bucking include thoracolumbar, sternal, rib, neuropathic and primary hindlimb lameness.

According to Dyson, horse with sacroiliac pain often present with fly bucking where the back is extended and the hind feet kick out.

Routine diagnostics and imaging are mandatory in cases of suspected pain-related bucking to pinpoint the source of pain and institute appropriate treatment. Even with resolution of pain, however, the horse might continue to buck as a result of learned behavior. If when the horse was painful and bucked resulting in the rider being dislodged, the riding session terminated and the pain relieved, the horse might have learned along the way that bucking is “good.”

4. Rider Experience

“Bucking can be instigated by the confusing application of cues by the rider,” explained Dyson.

An unbalanced, apprehensive rider lacking confidence might contribute to bucking.

“These riders can transmit fear and not ‘ride a horse through.’ This highlights the importance of matching rider ability with the temperament and movement of the horse,” advised Dyson.

Further, if the rider falls off, this might frighten the horse and the bucking behavior can progress, becoming a learned behavior.

5. Tack Issues

As mentioned above, horses buck to avoid predation. Abnormal pressure on the withers region, for example, can induce bucking behavior. In addition, stimulating the “bucking reflex spot” in the lumbar (back) region can also induce bucking. Thus, excessively long saddles resting on this spot might provoke bucking. Veterinarians, trainers and riding instructors are encouraged to be familiar with tack fitting to help clients and patients resolve tack-related issues.

Management Recommendations

As we can see, the list of factors contributing to bucking is vast and varied. The underlying cause must be identified if you are to stop this dangerous behavior. Owners must not accept bucking behavior as normal in any way and should seek professional veterinary advice. Even with careful retraining under the guidance of an experienced trainer who truly understands learning theory, we need to accept that a small number of horses will not respond to retraining, prompting retirement or euthanasia.

“Retraining must be slow and progressive, with an understanding of learning theory. Rider safety must always be of paramount importance,” concluded Dyson.