The instinctive sequence of behaviours an animal produces when faced with a perceived threat: freezing, fleeing, or fighting.

The flight response is conserved across vertebrates and represents one of the body’s most fundamental survival mechanisms. When an animal perceives a threat, the sympathetic nervous system activates almost instantly, the body mobilises for action, and one of three behavioural strategies emerges: freeze (stay still, often coupled with attempts at concealment), flee (escape from the threat), or fight (confront the threat directly).

In horses, the flight response is particularly well-developed because of their evolutionary history as prey animals on open grasslands. The default strategy for a horse facing a perceived threat is to flee, with freezing and fighting as alternatives when fleeing is not possible. This is one of the reasons that horse handling traditions across cultures have developed careful protocols for managing perceived threats, and one of the reasons the ISES First Principles of Horse Training explicitly warn against the elicitation of flight responses in training contexts.

In dogs, the flight response also operates but with more variation in default strategy depending on breed, history, and individual temperament. Some breeds are more inclined toward fight as a first response; others toward flight or freeze. The diversity reflects the long history of selective breeding for different working roles.

Across species, training that repeatedly triggers the flight response produces fearful, reactive animals and tends to generate exactly the behaviours it is trying to prevent. A horse who has been chased into compliance learns to fear the trainer’s approach. A dog who has been frightened into stopping a behaviour learns to fear similar situations. The behavioural science consensus is that training built around the flight response produces worse outcomes than training that keeps the animal in a calmer, more engaged state.

Modern applied animal training across species treats avoidance of flight-response elicitation as a foundational welfare principle.