TL;DR: Dominance theory and hierarchies in horse herds are complicated concepts, and the behaviour that we see that leads us to assume dominance/hierarchies often reflects a complex combination of variables that better explain what is going on than over-simplified terms that may not match a particular species’ natural ways and that may in fact reflect their responses to captivity conditions.
As we get started, I want to encourage a spirit of compassion, curiosity, and courage. This post isn’t about criticizing, judging, or shaming anyone who ascribes to dominance theory or the notion of horse hierarchies. Those of you who know me know that I try to broach difficult topics from a place of kindness, integrity, and humility. There is a lot that I don’t know, I’m not perfect, I make mistakes, and I’m always learning. It takes courage to be willing to re-examine something and consider different information that may contradict one’s existing beliefs without immediately dismissing the new information and doubling down on our position out of discomfort or defensiveness (cognitive dissonance), and possible underlying shame, embarrassment, or guilt. So if you are willing, let’s be explorers together.
Wild vs Captive Conditions
There is a difference between horses in the wild and horses in captivity conditions. Most people at the very least agree with this.
According to Rees (2018), in wild or feral horse populations, the individuals who tend to lead the way to food or water are usually the ones who have the strongest need for resources, namely the pregnant or lactating mares. This is likely where we got the idea of a “dominant/lead/boss mare”. However, that interpretation is not quite accurate; in wild/feral bands, dominance or leadership is not a role or position that is necessarily appointed for life. It’s not consistently the same mare or “just one” at the apex of a pyramid.
If you’ve ever felt “hangry”, then you will have a sense of this. Someone who is hungry and irritable because they need sustenance may be more dominant or aggressive/temperamental/decisive/driven to make decisions until sustenance has been obtained. It doesn’t mean they are always like that. Other variables come into play as well. For instance, a person who is “hangry” who is also dominant or more aggressive in other settings may reflect a combination of life adversities/trauma, temperament/personality traits, and genetic factors, as well as other environmental factors.
People that may act with appeasement around individuals demonstrating more dominant traits or behaviour isn’t a sign that that person is the appointed leader; rather, this may be an example of conflict avoidance or abandonment avoidance if they have learned to caretake and submit to preserve insecure or unsafe relationships. When we feel safe and are operating at full capacity, we might choose to lead or choose to acquiesce at different times. It’s not so rigid.
Similarly, hierarchies that form related to perceived dominance or aggression are seen in domesticated herds for a number of reasons related to captivity conditions as opposed to this being how horses “are”. I will divide the following variables into two categories, and list examples in no particular order.
Note: In debates about dominance theory/hierarchies, there is confusion in terminology. Sometimes the terms dominance, aggression, or leadership are used interchangeably, and dominant “behaviour” is sometimes misinterpreted as dominance as a “role” or position, which adds to the complexity. The variables below reflect this complexity.
A) Factors That May Influence Behaviour (in wild and/or captive horses)
- Pain, discomfort, illness, headaches, and head/brain injuries
- Hormone cycles
- Personality or temperament traits
- Gestation, lactation, raising a foal
- Age and ability
- Personality or temperament (e.g., is a horse that is more active/decisive in a herd one that is simply more extraverted, confident, or gregarious, or possibly one that is more nervous and needing to take charge)?
- Environmental conditions (weather, temperature, cover, terrain, climate, natural disasters, etc.)
B) Additional Factors Related to Captivity Conditions (that can compound the above)
- Controlled/limited resources: There is a relative decrease in space and resources in captivity compared to being in the wild (e.g., feed is put out and treats are high value novelties, which don’t occur in the wild and can create an impression of scarcity). Of course, there are horses suffering from malnourishment and deprivation in the wild in areas where there is a lack of resources, but these specific cases aside, overall there is a difference between the “unlimited” resources available in the wild versus what is controlled in captivity. Resource guarding occurs in response to this perceived scarcity. What horses in captivity are more likely to guard resources? This can reflect a number of the factors below and above. These factors below can also exist in the absence of resource guarding behaviour (“lack” of resources is not always a contributing variable to seemingly hierarchical patterns in captivity).
- Confinement or crowded conditions and lack of choice: Aggressive or dominant behaviour can reflect a sense of feeling trapped or not having enough space for comfort. Confinement or inadequate turnout can also result in sleep deprivation, which can lead to having a shorter fuse. Not getting to choose their own bands and sometimes being kept in areas where there isn’t a lot of space to create distance from disliked herd members that one is forced to be around can also result in frustration and dominant behaviour, as can limiting or thwarting the ability to engage in natural behaviour (foraging, roaming, socializing).
- Human handling or training methods: For e.g., does human aggression/dominant behaviour and/or the use of methods that involve power over/becoming the “leader” of the horse result in some horses becoming more like to bully others or engage in dominance behaviour with other horses? It’s an interesting idea. Certainly, believing in dominance theories may be reinforcing to humans (being in power/control may feel more comfortable than feeling powerless).
- At least one study (DeAraugo et al., 2014) has looked at the impacts of people’s attachment styles on their perception of the horse (and how they interpret horse behaviour), and in turn what training methods they are drawn to using. The resulting impact on the horses wasn’t studied (nor were the horses’ attachment styles), so further research is needed.
- A more recent study (Scholtz et al., 2022) looked at the parallels between communication patterns between family members and how those individuals also communicated with horses. How one is treated how relationship and communication dynamics unfold in one’s family may have a ripple effect on perceptions of horses and how we react/respond to them.
- The updated Five Domains of Animal Welfare model (Mellor et al., 2020) now includes human factors as potential sources of animal welfare and behaviour issues, including human handling, emotions, attitudes, training methods, and so on.
- There are multiple studies (too many to list here) looking at the impacts of human physiological state on horse physiological state (e.g., heart rate variability, cortisol, behavioural observation, etc.) in different contexts.
- A full review of dominance theory in relation to horse training methods can be found in Hartmann et al. (2017).
- Early weaning: Maternal/social deprivation (early attachment ruptures) in infants of many species increases the risk for aggression, addictions, difficulties socializing and with attachment, and other challenges.
- Cues or conditions of “unsafety”: Feeling fearful or unsafe can result in aggression (fight as a survival response to perceived danger). Repeated experiences of feeling unsafe or aggressed (by humans or other horses), and repeated boundary intrusions/ruptures, may result in a nervous system that is focused more on signs of danger and is more easily ready to react in self-protection (at other times or in other individuals, other protective responses kick in, such as flight, freeze, collapse, appeasement/fawn, etc.). These cues can also be environmental (certain noises or other sensory stimulation can trip the nervous system into feeling unsafe and potentially more irritable or on guard).
- Different attachment styles and a sense of feeling fearful may result in some horses bonding with other horses that are more confident or regulated to experience co-regulation, comfort, security, or protection. Proximity seeking to a calm or confident horse doesn’t mean that the calm or confident horse is automatically dominant or higher in a hierarchy. Also, it is possible that more nervous or insecure horses may defer decision-making to a more confident friend. And if such a calm/confident horse becomes « leader » in what appears to be more of a fixed role within the group, it is possible that this is more reflective of the herd’s needs for co-regulation and security (consistency, predictability, etc.) due to the herd’s individual and collective past experiences (what might this say about the horses in that specific group?).
- Similarly, horses that tend to take on more of a sentinel or protective role may have personality traits, nervous system state patterns, or life experiences that lead them to behave that way (e.g., horse that is hypervigilant or sleep deprived or more worried or possibly more sensitive/nurturing), but that doesn’t imply a strict hierarchy or that others might not take on sentinel roles or engage in protective behaviour at times too.
- Stimulus stacking: Experiencing too many stimuli or demands without relief or resolution of the stress response that occurs in relation to each stimulus can result in a nervous system that reacts suddenly or intensely to even minor intrusions or disturbances as a result of being overwhelmed (also called trigger stacking). If a nervous system is more likely to “freeze”, become stoic, or appease/comply in response to stress, it may reach a point where it winds up beyond threshold and reacts in surprising or unexpected ways that may be misinterpreted as dominance.
- Having a narrow window of tolerance, low frustration tolerance, or operating in a “faux window” (Kain & Terrell, 2018) can result in a propensity for certain behaviours due to lack of capacity within the nervous system.
- Other stressors: Aggression may also be linked to other experiences, directly or indirectly, such as grief, sexual frustration, aggressive play, sleep deprivation, and so on.
- Selective breeding / genetics: Horse breeding in captivity has resulted in specific breeds with specific traits, some of which can result in different temperament profiles and propensities to react in different ways that may appear dominant.
- Chronic stress and nervous system states: With some exceptions, in the wild, animals are exposed to stressors that are short-lived, and survival energy that was mobilized to deal with stress or danger usually deactivates and the animal returns to homeostasis. If an animal goes into freeze or collapse, then if the conditions support it, it eventually thaws back into aliveness when the danger or threat has passed (Levine, 1997; Levine, 2010). There’s a natural ebb and flow to this pattern of contraction and expansion in the body. This doesn’t mean that animals in the wild don’t experience trauma, but rather that the conditions in the wild often support this rebalancing to occur after stressful events. However, in captivity, stressors are usually more complicated, chronic, and don’t resolve as easily. Some horses that may exhibit dominance may be horses that are more easily activated into a stress or survival response as a result of adversity or captivity conditions (hyper-arousal as a baseline, increased allostatic load). Fixed nervous system patterns result in specific behaviours and may contribute to being in fixed “roles”. In some organisms, there can be a lack of tolerance for calm and letting go (feels safer to be on guard and in control).
- Sexism and misogyny: Mares and their behaviour are often misperceived and may be treated differently due to societally held misogyny/sexism. Dashper et al. (2018) looked at people’s preferences for geldings over mares and how stereotypes related to sex may affect beliefs and subsequent handling/training of mares. This may in some ways influence perceptions related to lead mares (females as bossy, females as nurturers/caretakers, etc.) due to anthropomorphizing human gender roles. E.g., geldings also can take on “lead” or dominant positions within captive herds as a result of the variables in this list.
- Equine management practices: In many places, geldings and mares are housed separately, which may result in different behaviours such as hierarchies as adaptations to circumstances.
And so on.
Complexity is the Spice of Life
There are many potential intersecting variables that add nuance, so having a broader lens that also looks at adversity, trauma, environmental factors, temperament, and genetics is important. When I observe horses or really any mammal, I can’t un-see any of the variables above. Simplifying things down to dominance and hierarchies for me doesn’t quite fit because all of these other pieces are potentially part of the picture in complex ways, with feed forward and feedback loops playing out on levels that may be hard to detect or tease apart.
Dominance behaviour or hierarchies in captivity usually reflect conflict behaviour, attempts at conflict avoidance, and may reflect additional pieces unrelated to conflict at all. Captivity behaviour is about different personalities and nervous systems navigating and living within various parameters that wouldn’t exist in the wild typically to the best of their abilities. This would mean that to claim that horses are naturally hierarchical is no more accurate than saying horses are conflictual or are « flight animals » (De Giorgio & de Giorgio-Schoorl, 2017). If what we are seeing is more about the captivity conditions than their true natures when under optimal or natural conditions, then this would be a version of diagnostic overshadowing.
It’s important to note that anecdotes of dominant horses within an apparent hierarchy are typically of horses in captivity conditions. Horses in captivity have been observed to experience up to 20x as much conflict than horses in the wild (Rees, 2018), which speaks to captivity conditions as being the explanation. This implies that any changes within this complex system of variables can lead to shifts in behaviour and therefore shifts within the herd (systems theory), since the captivity behaviour being observed isn’t ethnologically what would occur under natural conditions. Systems do like to maintain the status quo, but that’s for ease of effort as opposed to a sign that a hierarchy is somehow the natural order of things. There are other forms of status quo that are not hierarchical, such as the affiliative-based herds spoken about by Rees (2018). Whatever « hierarchy » may be seen may reflect a particular group’s way of finding the most cost-effective way of adapting given all the givens.
The risk of keeping a dominance theory/hierarchies lens is that in over-simplifying what is going on, we risk missing out on opportunities to create changes that might lead to greater comfort, sense of safety, and regulation. By assuming that this is simply how things are, we might fail to recognize signs or cues of areas where we could intervene differently or make environmental changes that could result in different behaviour. For instance, if what is being interpreted as dominance behaviour or a sign of a hierarchy reflects fear, sleep deprivation, dysregulation, or attachment difficulties, then remaining at the level of believing that horses are simply in specific positions or roles may mask welfare or emotional wellness issues that could be improved. Ultimately, the presence of dominant behaviour or hierarchies isn’t necessarily a sign that there are welfare issues, and a captive herd may indeed have found stability within the particular formation it has adopted. But we can’t assume that this is true in all situations at all times, and even if welfare appears acceptable, there are always things that can be tweaked when we pay attention in a more nuanced way.
Apples and Oranges
Some have proposed that the idea of a dominant or lead female makes sense in herd animals where males are more transient. This certainly appears to be true for elephants, that have herds made up of families of females, with teen and breeding males as transient or forming male bands led by elder males. However, Rees (2018) and those that study or rescue wild mustangs in North America, for instance, observe that stallions generally have family bands and that bands are not matriarchal or hierarchical beyond adults teaching or instructing youngsters (which doesn’t strictly fall upon the mothers but other older band members as well). Younger males are either chased away or leave to form their own bands, but bands don’t necessarily just have one resident male or no male at all. Certainly there are skirmishes around mating season and when outside males try to obtain mares for their own bands, but again this is context-specific and the responses within the herd to threats or changes to who the breeding stallion is are less about appointed roles and more about the different variables listed under (A) above. Also, females sometimes choose to leave bands of their own volition to follow a different stallion, which doesn’t necessarily result in conflict. If a band temporarily loses its resident stallion for whatever reason, the remaining system likely adjusts based on the different variables that are within the herd (temperaments, needs for resources, experience with navigating terrain and locating protected/resource-rich areas, who is feeling well, etc.) as opposed to defaulting to a single member.
Cattle offer an interesting comparison. They are similar to horses in that they are a captive species (even if left to roam on vast ranch land, they are still “managed”). Herds of cattle are generally limited to cows (with or without their offspring, depending on whether they are dairy or meat cattle) and heifers (castrated steer are kept with females or separated). Bulls are kept separated until breeding season when/if they are reintroduced, which is different from elephants in that this reflects a livestock management practice. As a result, dominance and hierarchies in cattle may reflect a combination of variables from (A) and (B) above. For example, when cattle « hump » other cattle: is this dominance or an attempt at establishing a hierarchy, or is it due to sexual frustration since bulls are kept apart, or possibly frustration due to crowded conditions?
Bonobos (related to chimps) are sometimes cited as a female-led group evidence of hierarchies, but they are omnivorous primates and considered predators, so different dynamics may be at play. Similarly, many whales have female-led pods (male killer whales for instance remain in their mothers’ pods as brothers and sons, leaving to breed), but they are carnivorous predators. Comparing wild predator behaviour to domesticated prey behaviour is not quite relevant.
While I encourage recognizing the similarities in various mammalian species (what I call mammaliomorphism) in terms of how they respond to adversity to emphasize that trauma is not the exclusive domain of humans, it is also important to recognize differences where they exist. We use the term anthropomorphism to describe when truly human-specific traits are misapplied to other species. There does not appear to be a term when traits or features of another species are misapplied to a different species, though this is what appears to happen when bringing in comparisons that don’t quite line up.
Finally, there is a difference between matriarchal and matrilineal groups. Matrilineal groups are based around kinship related to the mother’s bloodline/family. Matriarchal groups are a form of societal structure where females occupy leadership roles. Sometimes the two coincide, but not necessarily, and sometimes the term matriarchal is used when in fact matrilineal is meant. Those in favour of hierarchies and dominance theory in horses sometimes cite matriarchal groups as an example, but some of these groups may in fact be matrilineal and have a different organizational structure that may reflect more fluidity in terms of social roles. So citing matriarchy as evidence of hierarchies (which do exist, that’s not in question) may not be a solid argument in every case or one that specifically applies to horses the way it does with other species.
There is so much more than meets the eye on this topic.
Holding a flexible, curious view and spaciousness of awareness is important to avoid the risk of confirmation bias (« this is what I believe so that must explain what I am seeing. »). Being curious and being willing to sit in uncertainty is important – it’s reinforcing and more comfortable sometimes to latch on to simple explanations (the illusion of certainty and having the « right » answer can feel safer or more comfortable than not knowing). Sometimes the simplest explanation is accurate (think Occam’s Razor), but the world is also quite complex. We have quadrillions of neurons and synaptic connections firing and wiring all the time. It’s humbling and really awe-inspiring. When we consider these other variables, what we « see » changes because we’re looking at it through a different lens.
If you find yourself defaulting to simple explanations of dominance or hierarchies, see if you can notice the current beneath the surface. What lies beneath that? And what happens next – what new directions are possible – when you put your attention there?