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The social lives of horses

  • Ethology

by Rachele Malavasi, scientific popularizer on horse behavior and management of its welfare

Socialising is one of the strongest natural instincts in horses: living a peaceful life in herds is the starting point of their well-being. Years of selective breeding have not changed this need in favour of life with humans: through selection, horses have been bred to be more docile (i.e. more inclined to be led), but this would have been impossible if they were forced to live outside of a herd. Everything in horses is oriented towards social life, even their brain, whose gyrification index* is among the highest in mammals: according to scientists this is probably due to the high social complexity1.

Functional groups: go where your heart takes you

Let's start from the grassroots: the very core of a horse’s social life is the group, not the herd as it is usually called. A herd is made up of different groups and is a temporary association based on immediate survival needs (such as protection from predators) as well as on ensuring the objective of a better life (getting to know new personalities, acquiring skills through observation of other groups, opportunities to change group, etc).

There are many types of groups2,3. The “natal group” is the horse’s family and is the group they were born into; the "family group” is the group in which horses spend their adult life. In any case, the group usually consists of one or more adult males, 5 or 6 females, and foals up to 2-3 years old. The natal group is just the beginning of the life path of a horse, who changes “friends” depending on its age in a way which is very similar to ours: in fact, the social structure of both humans and horses (as well as of some cetaceans, social carnivore, bats, elephants and other species) is arranged into "functional groups": the different stages of growth that an animal passes through during its life cycle calls for a different group that enables the acquisition of specific skills.

How do they move from one group to another? Why leave the old when you don't know what the new has to offer? As zooanthropologist Roberto Marchesini explains, when an individual is faced with something that attracts him but that he cannot obtain due to a lack of skills, he must deal with a 'knowledge gap', a gap that he will try to fill in order to achieve his goals. Some species may be more aware of this process, as humans are, whilst we don’t know the level of awareness of other species. However, what we can say is that a horse realises when he’s unable to achieve something and is attracted to all contexts that will facilitate the acquisition of new skills in that area. For example, a young foal who is still living in his natal group and who comes across a group of young horses  might not be accepted by the group. Possibly because he is not yet confident enough: so he will feel attracted to all those contexts where he puts himself to the test, thus gaining confidence. Nature will ensure that these new but addressable challenges will bring him joy (i.e. stimulate the production of hormones such as dopamine and serotonin), making him willing to continue facing new challenges. When he meets the group of young horses again, he may be ready and accepted. Should he meet a female horse, he will go through the same process: he might not be able to conquer her and then a knowledge gap will be created, resulting in the need to acquire courtship skills. These processes, that have a clear evolutive nature and are rooted in biology, make us understand that learning is not something that is handed down from on high, but is the result of the desire to adapt to the social environment.

The adolescence of a horse

Most young stallions leave their natal group to join a group of peers, an all-male group mainly between the age of 3 and 7. Alternatively, they may form mixed-sex groups of youngsters, or "mixed groups", in which young males and young females live together without reproducing — although they have reached their physiological sexual maturity — because they are still unable to carry out the correct courtship rituals. The adolescent phase for a horse plays a key role in confirming his identity and allowing him to acquire useful skills for adulthood, in much the same way as it does for human adolescents.

When they feel ready, young horses belonging to a peer or mixed group may try to live together with adult females and males in a group of two or three individuals. These small groups often fail because the youngsters are inexperienced, are unable to protect the female or are too aggressive, and return to the groups where they came from.

Some young horses take a different route, choosing to move directly from the natal group to a new family group, without passing through a group of peers.In other words, they propose themselves as an ally of the resident stallion of an already existing group. An advantage for all: this will make it possible for young horses to learn directly from an expert horse how to manage the group and experiment their courting abilities with the less desirable females; as far as the resident stallion is concerned, having an ally is very useful when the group is attacked by other stallions, because the ally is the first to deal with the intruder and usually fails, giving the resident both the opportunity to study the moves of the intruder before challenging him physically, and to make a good impression with the females as he is generally able to resolve the situation.Does this mean that there’s only one stallion per group? Not necessarily. In fact groups with more than one stallion are about 25% of the total. 4.

Young mares who leave the natal group are never alone: they either join an existing family group or mixed groups. Female horses create strong bonds that can last for up to ten years: it is more likely for a stallion to be moved away by another suitor, while females tend to stay together. However, if they do not like the new stallion, they can decide to abandon him or stay with the old one even if he has been beaten. In nature, the strongest rarely wins but rather the one who can mediate, and not only in equine communities.

Is a domestic group so different?

It is so different that we cannot even talk about a real "group": it involves no migration, no stallions, no possibility of choosing who to live with. However, even in the domestic environment it is possible to recreate groups just like in nature by having adults, young and old horses of both genders live together, so that many contexts are created in which they can express themselves and measure up with other personalities5. In fact the above description of the social structure shows a strong need for horses to have varied, stimulating lives, not in terms of exercises but rich in opportunities to express themselves and to seek their own way. A horse will want to be a mediator, an explorer, a sentinel, a protector... depending on the group he lives with and the challenges it faces. A horse that lives always with the same creature expresses his individuality only partially, as if we spent our lives hanging out with only one person. Those who believe that horses don’t like social life has maybe never seen their horse develop appropriate skills to interact with a group and only then to spend time with other horses: it is impossible then for a horse to choose to live an isolated life!

  1. Schmidt, M. J., Knemeyer, C., & Heinsen, H. (2019).Neuroanatomy of the equine brain as revealed by high-field (3Tesla) magnetic-resonance-imaging.PloS one, 14(4), e0213814.
  2. Rubenstein ,D., Nunez, C.,2009.Sociality and reproductive skew in horses and zebras.In:Hager, R., Jones, C. (Eds.), Reproductive Skew in Vertebrates:Proximate and Ultimate Causes.Cambridge University Press, Cambridge.
  3. Ransom, J. I., & Kaczensky, P. (Eds.).(2016). Wild equids:Ecology, management, and conservation.JHU Press.
  4. Ringhofer, M., Inoue, S., Mendonça, R. S., Pereira, C., Matsuzawa, T., Hirata, S., & Yamamoto, S. (2017).Comparison of the social systems of primates and feral horses: data from a newly established horse research site on Serra D’Arga, northern Portugal.Primates, 58(4), 479-484.
  5. Sigurjónsdóttir, H., & Haraldsson, H. (2019).Significance of group composition for the welfare of pastured horses.Animals, 9(1), 14.

* The gyrification index measures the amount of gyri, sulci and fissures in the brain



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