Abnormal aggression in horses is usually caused by humans, according to two Polish researchers who reviewed aggressive behaviour in the species.
Katarzyna Olcsak and Czeslaw Kloceck, writing in the Journal of Interdisciplinary Research, said inappropriate handling of dominant or fearful horses can exacerbate problems.
The pair, from the University of Agriculture in Krakow, set out in their review to describe different types of aggressive behaviour in horses.
“Knowledge about reasons and signs of aggressiveness in horses is essential to improve horse management, welfare and both human and horse safety,” they said. Environmental and biological aspects of aggression also needed to be considered.
The influence of bloodlines, nervous system structure, hormone levels and human interaction were strongly connected with aggressive behaviors, they wrote.
There were, they said, various types of aggression, from natural behaviours that centred around establishing dominance and hierarchy, to abnormal forms, which included aggression against offspring and self-directed aggression.
The pair said the most common forms of aggression came from the desire for dominance, or arose through fear, hormonal disorders, unsuitable living conditions or disease.
The pair traversed the biological aspects of aggression, including the role or genetics, the nervous system and hormones, before discussing environmental influences.
Turning to dominance, the pair said stable hierarchies within groups of horses reduced the number of injuries and energy lost.
“It is suggested that body mass, physical condition, age, previous agonistic interactions, parents’ place in the hierarchy and the level of individual aggression are factors that influence place in the hierarchy.
“Aggressive behavior is the most important factor that places an individual in the herd.
“Once the hierarchy is established, aggression from most dominant horses is rarely observed because other horses respect their dominance.”
More aggression is seen after a new horse enters the group until a new hierarchy is established.
The duration of aggressive behaviours depended on the new horse’s temperament and its level of aggression.
The pair said aggression in horses was an important issue which was still not fully understood. More research was needed to learn more about the factors that drove it.
Better knowledge in this area would not only improve the wellbeing of horses, but improve the safety of people around them, they said.
Abnormal aggression was usually triggered by humans, they reported, through the likes of inappropriate handling of dominant or fearful animals.
“Defensive aggression may occur if a horse has no possibility to escape. Nevertheless, equestrians and breeders should be able to recognise behavioral signs of a horse’s mental state to improve their welfare.”
Poor management – keeping horses in too small an area, isolating them, or feeding them inappropriately – may also induce aggression.
“If there is genetically determined ‘malice’, it occurs rarely,” they said.
Some horses, notably stallions, may try to dominate people.
“Consistent, confident handling will do a lot to reduce dominant behaviors,” they wrote.
A review of aggressive behaviour in horses.
Katarzyna Olcsak and Czeslaw Kloceck
The full review can be read here.