Aggression in horses is a common reason for owners to seek help from equine behaviourists. Why do horses behave aggressively, and what can be done to change aggressive behaviour?
Aggression
While aggression is a normal part of horse behaviour, by nature, horses are not an overly aggressive species. In their natural state, they spend much more time engaging in affiliative behaviours than they do in agonistic behaviours. Affiliative behaviours are ones that promote harmony between individuals, while agonistic behaviours are defensive or aggressive behaviours which serve to increase distance between individuals.
Behaving aggressively is a 'costly' endeavor: fighting burns precious calories; it carries with it the risk of injury or death; it can attract predators; it results in increased physical and psychological stress. For social animals like horses, who rely on others for safety, it also carries a real risk of damaging vital social bonds.
Horses will behave aggressively for a number of reasons, such as:
if threatened or frightened
when in pain
if frustrated
as a result of artificially created social groupings (e.g. in a boarding facility)
as a result of inadequate early socialization
as a result of certain medical conditions or diseases
in an effort to control access to resources, which may be restricted, such as food, breeding partners, water, space etc.
Aggressive behaviour may be subtle, such as pinned ears, or kick threats. It may also take the form of more active behaviours, such as chasing, biting, kicking or striking. Humans are not as adept at reading horse behaviour as horses are, and therefore may be oblivious to subtle signs of aggressive behaviour.
Aggression in horses towards humans is not a sign of dominance, or trying to maintain 'alpha' or 'head horse' status. While the belief that horse herds have linear hierarchies was debunked long-ago, it's a incorrect notion that sadly still persists. Numerous studies have shown that there is no one horse that makes all the decisions, or uses aggression to lead the others. What dominance is defined as, is a temporary relationship state between two animals to determine who will control access to a resource.
Horses may behave aggressively towards people if they feel threatened, or if they are trying to escape or avoid doing what the person wants them to do. They may also behave aggressively as a result of previous experience. For example, a person approaches with a bucket of grain, the horse pins their ears, the person puts the grain down and retreats. In such instances, it is critical to determine the original root cause of the aggressive behaviour and address that, rather than simply trying to suppress the current aggressive behaviour using punishment. A horse who behaves aggressively when a human approaches with grain may have an undiagnosed ulcer, or may be being fed in ways that cause physical and mental distress (i.e. set feedings, with periods of fasting in between) leading the horse to feel frustration. Punishment can only tell an animal what not to do, and it can't resolve the reason the behaviour occurred in the first place.
Resolving aggression in horses
Equine behaviourists and horse behaviour consultants take a multi-pronged approach to resolving aggression: they determine and address why the behaviour is happening, they identify and address any factors that are maintaining the behaviour, and they teach the horse how they should behave instead. In some instances, the horse's owner or trainer may also need to change their behaviour, if it contributes to causing the horse to behave aggressively.
In general, it is not necessary to use punishment to address aggressive behaviour in horses. Using punishment is also not advised by animal behaviour specialists, as it can worsen aggressive behaviour, or create additional unwanted behaviour problems. Instead, equine behaviourists and horse behaviour consultants use effective - and horse-friendly - methods to successfully resolve even the most serious aggression cases.
Summary
Horses behaving aggressively are not only dangerous to be around, their behaviour usually also indicates a high level of stress and unhappiness. If your horse is behaving aggressively, first have your veterinarian rule out physical or medical reasons for the behaviour. Next, seek the help of a qualified equine behaviourist or horse behaviour consultant to help you safely resolve the issue.