Dominance and Hierarchy
Last revised April 12, 2017.
Submission is being expressed by a young dark gray male in center and directed toward the larger, dominant male (foremost), who is displaying threat behavior associated with dominance.1
I have argued that a herd of horses is much like a school of fish or flock of birds, leaderless and choosing a course of action via collective decision making. I have argued that “respect” as is normally meant by humans, does not exist in the horse, and that humans often use it as a euphemism for “fear”. I do not dispute the existence of “dominance” in a herd of horses, but I have questions about what it is and whether the concept is useful. Thirty years ago, researchers were far from a consensus on how to define and measure dominance, and little has changed since then.2 Anything gets harder to talk about when we can’t agree on what it is.
Some definitions suggest that any social group of animals that uses aggressive contests over resources develops dominance relationships. In such definitions, the dominance system comes about because of individual variation in aggressiveness. But these definitions imply that aggressiveness — not dominance — is a basic quality of the individual, and that dominance is a quality of relationships between individuals.3
When I moved my horse and mule to a new farm with many bands in separate pastures, I asked that my mellow 17 year old thoroughbred be placed in a herd of calm horses who had no interest in wrassling. This small herd seems to get along perfectly well. All can come to any limited resource, such as gate, hay, or water, without hesitation, without any scrambling with other users of the resource. I have never seen any roughhousing in this pasture, or signs of it in my horse’s coat. Are we talking about a herd in which no dominance is displayed because none of the horses are aggressive — or because the valued resources are so abundant that there need be no competition for them? Does this mean that dominance is not always needed in a herd?
An important study by researchers at Cornell4 found that aggression was apparently the most important determinant of dominance in a herd of horses, that it occurred where resources were limited (such as food or drinking water), and that mares were often the most aggressive in the herd at such times.
I believe that horses in a herd are peers when there are unlimited resources, and that dominance and rank only arise to prevent confrontations over limited resources. A limited resource can be anything: a limited amount of space in the run-in shed in a winter storm or under a shady tree on a hot day, a spot at the puddle or trough or hay bale. Aggression subsides when requirements are met. When they are both well fed, squirrels and crows can share bird feeders, and the lion can lie down with the lamb. But when someone is hungry, there can be trouble.
A dominance hierarchy is a social structure that has developed through a series of conflicts between pairs of individuals, in which one established a higher rank than the other. High levels of testosterone and aggressiveness contribute to achieving a high social ranking. The conditions under which the conflicts occur also have an impact: if the territory is more familiar to one than the other, the former may feel greater confidence upon entering the conflict, and this confidence will sway the outcome.
The Value of Social Rank
Horses are like all other animals, programmed to avoid injury if possible. No animal can afford to be injured. Fighting can be dangerous, because even the strongest, bravest, most skilled warrior can be injured, and injury can always lead to death.
This favors the creation of a social structure in which rank determines order of access to resources. There are no species in which two individuals have to fight more than once to determine their relative rank. Perhaps our own species is an exception to this principle. Defeated boxers, wrestlers, and martial arts warriors all want rematches, and can’t accept the rank that results from loss.
Once rank is determined, it defines the order in which the individuals may access the resources.
Dominance hierarchies in horses regulate who gets to come in first from the field, who gets the best spot at the hay feeder, who will fit into the run-in shed. While dominance is established by one or more conflicts between individuals, it is generally maintained by threat alone. The dominant animal threatens, the less dominant animal submits, and the order is maintained. A dominance hierarchy results in less roughhousing than if horses needed to fight for the hay or run-in shed every day. So such hierarchies are good things, overall.
Of course, a dominance hierarchy is not perfect. Among dwarf mongoose, a dominant female is the first in line for food, and gets the sole right to reproduce. But it turns out that she lives with more stress than those she dominates as measured by the cortisol levels in her urine. In male and female wild dogs, dominant dogs have higher cortisol levels in their feces. In baboons, dominance results in a higher rate of miscarriages. In dogs and mongooses, chronic stress may lead to a shorter life for the alpha animals. In birds with territories, males have more corticosterone and testosterone than those males lacking territories.5 Being on top has its downside.
Dominance hierarchies (in mares at least) appear to be stable over the years. One study that looked at mares over an 18 month period found that the hierarchy within the herd remained stable during that interval.6 Adding a new horse to a herd forces the herd to reassess the dominance hierarchy. Every horse must undergo a challenge with the newcomer in order to establish a new hierarchy. The new horse often, though not always, will find itself near the bottom of the hierarchy, because each long-term member of the herd has a confidence that comes with familiarity with the herd and with the pasture.
Horses are not Wolves
Throughout this book I’ve noted patterns of behavior in various species. Just a paragraph or two ago, I mentioned dwarf mongoose, wild dogs, baboons, and birds. I have tried to do this carefully, to demonstrate similarities and differences. I realize that my care may not have been evident to you, and you might be headed toward the notion that “all animals are alike.” They are not.
Sometimes our knowledge of one species colors our judgment about another. Our own model for dominance, for instance, may come from working in an office or watching a presidential election or watching our dog at the doggie playground. But your horse has no idea that he is supposed to be dominant, or that dominance is important. He’s been out of the loop.
In a species like the dwarf mongoose, dominance determines who gets to reproduce. In a horse, it does not. All of the stallions in a band may get to father a foal or two, and all of the mares will get to mother one.7 In nature, a stream will accommodate more drinking horses than a trough will in your pasture, so when it is time for a drink, everyone can do this, even if some are concerned about their personal space. For a band of feral horses, resources are far less limited than in a small pasture. (For example, many pastures have only a single tree or two to stand under on a hot summer day. In the wild, there are lots of trees.) Struggles for dominance occur in your pasture whenever a horses is added or removed from the group. In the wild, there is more group stability, and so there will be less effort expended in determining rank. Dominating and submitting exists in our pastures, but rank is not anywhere near as important to your horse as you might think.
By the way: the horse’s response to domination is not merely submitting. It is active avoidance. If you are wondering why your horse doesn’t meet you at the gate when you come along, think about this.
Lining Up and Dominance
I was once in a “T-Group”, a long time ago in a galaxy far, far away. Strangers in the gym were divided into a few dozen groups of about 10 each, and told to line up in order of aggressiveness. Of course, because none of us knew the others in our group, we could not do this based on prior knowledge. I am not the most aggressive person on the planet, but I do like acting in a way that is defensible. I reasoned that if I meekly allowed the others in the group to line up the way they thought, I could find myself in an incorrect position. If I decided I was least aggressive, someone else might decide the same, and I might be pushed to the middle of the line. The only position in the line that could be certified correct was the front. I took that position, and had to knock another guy to the floor to hold it.
That did not make me a leader. It made me an idiot for participating in this exercise. But at least I had the only position that was provably correct.
Cattle typically walk from one grazing, watering, or resting place on a well-worn path, single file. There are studies that find that the order of the line along this path is fairly stable over time — that is, some choose to be near the front of the line, some near the back. The notion that those at the front of the line have higher rank is at least shaken by the observation that calves stick close to their moms, and they are certainly not of higher rank than a following adult. It seems unwise to pronounce a line of cattle moving single file along a trail as being “led” by the one in the front. If there is any leadership at all, it is invested in every cow but the last one, because in single file, all but the last are followed by the one behind.
Dominance isn’t leadership. Another study, “Synchronization and leadership in switches between resting and activity in a beef cattle herd—A case study”, found that “dominance status of an individual cow did not correlate with mean interval between her activity switches (lying down or standing up) and activity switches of the next cow, indicating that there were no leading animals initiating switches in activity in our herd.8” In a herd of cattle, there is no leader.
Dominance doesn’t correlate with leadership in flocks of ducks9 or herds of sheep10 or goats11 or cattle.12
Stability in lineups might be out of habit. Stable organization of single-file lines are common in domesticated herd animals, including cows,13 sheep,14 goats15 and pigs.16 Those animals found near the front today will likely be found near the front tomorrow.
In a study of young Hereford cattle who were repeatedly weighed, researchers reported “During the experiment the cattle developed a significant weighing order which was unrelated to sex, weight, horned condition, or the effect of weaning. It is suggested that this weighing order is not related to social dominance… The behaviour of these cattle immediately before entering the scales was consistent for a number of individuals. It was not a satisfactory measure of temperament and appeared to be related to the design and installation of the scales.17” Another clue that lineups are formed out of habit: while heifers usually line up in the same order when traveling, when entering a pasture or grazing, cattle disperse independently.18
Camels are like cows. Norbert Schulte and Hans Klingel must have had fun studying a herd of captive camels in Kenya. After many hours of observation, they conclude “No stable leadership was observed, but individual preferences in the walking order existed when the camels left and entered the enclosure.19” So camels prefer to line up in a familiar order when walking somewhere, but have no stable leadership.
Stability in lineups might derive from differences in experience and familiarity. Those found near the front of a line may simply be older and more experienced with this route, and thus more comfortable (or less uncomfortable) in stepping forward. One study concludes those at the front of a line of moving goats were likely to be a little older and to have been raised in the area, and were not the most dominant.20 Animals for whom a route is most familiar should be expected to be most comfortable with it, and least hesitant in stepping forward to follow it. So the single file line might gain its stability from differing degrees of familiarity or comfort/anxiety.
No single leader. A study with the title “Graded leadership by dominant animals in a herd of female beef cattle on pasture” found that “foraging and short-distance traveling movements by female beef cattle are not led by any particular individual but rather are influenced by a graded type of leadership; that is, the more dominant a cow is, the stronger the influence it may have on the movements of the herd.21” A herd of cattle has no single leader. In feral horses, there is a lack of consistent leadership within a situation or across situations.22
Bulls don’t lead. Ganders don’t lead. Stallions don’t lead. I won’t repeat what I’ve already said about stallions in the chapter on “The Herd” — other studies also point to the notion that stallions are not normally dominant in a hierarchy. One study found that when a herd of semi-wild cattle was forced to move forward for dipping (walking through a deep vat of liquid pesticide to kill ticks), older cattle, experienced and familiar with the procedure, were likely to go to the front, and less experienced ones hung back, but during voluntary movements, there was no relation between age or dominance on the position the cow took when traveling single file. This herd included a bull, who always followed the group unless there was an encounter with strange cattle — in which case he moved to the front and tried to keep the two groups separate.23 Bulls are much like Red Deer bucks, who bring up the rear when the herd is traveling.24 In this way cattle and deer are much like Canada Geese. During grazing, males stand on guard. When a predator approaches, they move in for a confrontation. When the flock moves, each male trails his wife in the air. With voluntary movement in herds of cattle or flocks of birds, dominance may not matter in leadership.
Independent action does not mean leadership. If an animal walks away from the herd, do others follow? Sometimes, but not always. Either independent action is not leadership, or it is not effective leadership. Working with pigs, Meese and Ewbank observed that “animals leaving the group did not always stimulate following amongst the remainder”.25
Leadership requires followership for us to take note. Joel Berger notes that “the origin of a leader for a walking pattern frequently was the individual that merely assumed the initiative and walked. When others followed, the lead horse continued, but when there were no followers, which often was the case, the horse soon stopped.26” A similar situation occurs in the American bison where leadership is dependent on group cooperation.27
In a study of cattle, there was no significant correlation between the likelihood of a cow walking off and anyone following. The researcher concludes “Switching from grazing to resting or from resting to grazing, as a herd, takes place as follows. When a certain cow initiates activities different from the remainder, it returns to the activities of the rest of the herd if the remainder do not follow. In a similar way “drifting” repeatedly occurs when a neighbour begins to follow, until the behavioural pattern of the whole group is changed. Thus, each animal is dependent on the herd. Leadership ranking, therefore, is not simply a measure of individual difference in reactivity to various stimuli. Voluntary movement of grazing cattle is the result of reciprocal action between the requirement of social interaction and the need for individual diurnal maintenance through grazing, ruminating, resting, drinking and so on.28” When a herd of cows begins to move, it acts much like a flock of geese described earlier, collectively making the decision.
What do we know about those that are found at the front of the line? In my T-group, we know it was the most assertive one who got to the front. But in studies of herds that are walking single file, the position at the front of a line of marching goats is not determined by dominance. Further, we know that stallions can push their band of mares — leading from the rear — as well as pulling from the front. Some have suggested that the most leadership is likely shown by the second from the front of the line.29 If this is so, then using position in a line to determine rank or leadership becomes awkward.
Another way to infer rank
Dominance is not readily seen in feral horses. Spend a few hundred hours observing them, and you’ll likely learn that a free-ranging equine society functions on kinship, recognition, and respecting each other’s space. Watch carefully, and you’ll likely find it easier to spot an avoidance order than to spot any sign of aggressiveness and dominance.30
There is a horse that gets to eat at his chosen spot, or gets his choice of position in the run-in shed, or gets to drink when he wants, or gets to decide where he will stand when at the gate. But he is not a leader. He is dominant. His dominance could come from a variety of factors, which I’ll look at below.
In horses, dominating is done through kicks (threatened and those that make contact), bites (threatened or attempted or delivered), and head bumps. Submitting is indicated by backing away and keeping away. Because horses rarely fight, a confrontation between two horses usually consists of one showing dominance and the other showing submission.
Dominance might be imagined to be “situational” — one horse might choose to dominate another in one situation, but not in some other. But it appears that dominance-submissiveness is a quality which a horse “has”, and displays regardless of the situation. In one study of dominance in horses, there was a strong negative correlation between the number of attacks a horse made and the number it received.31 No one picks on the bully.
Factors in Dominance
Horses recognize each other by sight, by sound, and by scent. Of these, scent is probably the most important. If you are going to introduce a horse to a herd, you should consider scooping up some soil from the area where the herd roles, and applying it to his back and neck. This will make him smell more familiar, and lower the aggression he triggers in the others.
Dominance hierarchies in a small, established herd are usually transitive (linear): If A dominates B, and B dominates C, then A dominates C. This is an example of the “transitive property of inequalities.” But intransitive (non-linear) hierarchies (A dominates B, B dominates C, and C dominates A) happen in large herds, especially near the bottom of the hierarchy.32 And when resources are abundant, dominance hierarchies are hard to detect.
Dominance, it turns out, is not a personality trait. It is not a quality of the horse. We say a horse is dominant when, in an interaction, it behaves confidently, assertively, perhaps aggressively, and the other party — horse or human — yields. Confidence and aggressiveness underlie much of all behavior, along with age, sex, size, strength, health, intelligence. Each of these qualities accompany our horse through life, some changing (age, health, strength), some invariant (sex, intelligence). And so a horse’s position in a hierarchy may shift over time, as the determinants of dominance shift.
Dominance seems to transfer from mother to foal. In a study of stability of equine hierarchies in thoroughbred mares, researchers found that the foals of dominant mares tended to be dominant in their own age groups.33
Rank Matching. We normally think of dominance as active, and submission as passive. But moving away from an aggressive horse requires action, and it is more fair to all ranks to think about this differently. Aggressive horses often choose to spend time with each other, and those low in dominance seem to choose each other as best friends too.34 Friendship selection and maintenance is an active process, whether you are dominant or submissive. Birds of a feather flock together. Its the same with horses.
Age is a determinant of dominance rank in the horse35, especially if there are youngsters under the age of three, but it may or may not always matter among adult horses.36 In one important study, age and dominance were statistically indistinguishable. In studies of sheep37 and cattle,38 older ones are dominant over younger ones. Dominance and age are usually indistinguishable in gorillas, wolves, feral dogs, elephants, mongooses, and many other species.39 If there is a relationship between age and dominance, it is not always linear. In many groups, the old males are driven off, a terrible proof that they are no longer dominant. Tell me about it.
Sex. The jury is out on principles of dominance between mares. I think that it is aggression, rather than sex, that determines dominance, and that a mare can be more or less aggressive than a stallion. In some studies, stallions are dominant over mares,40 but mares have been seen to be dominant over stallions in other studies.41 I believe it likely that sex has nothing to do with it — that mares and stallions ignore sex when working out dominance, and attend more to size and aggressiveness.
Stallions have their own dominance hierarchies with other males, and mares have dominance hierarchies with other mares. In a study of dominance and aggression in feral mares, Allen Rutberg and Stacey Greenberg found:42
- Mares formed linear dominance hierarchies within bands. Bullying is not just for boys.
- Older mares usually dominated younger mares, and larger mares dominated smaller mares. But this seems to be an artifact of mares growing larger with age. Large mares initiated aggression more often than small mares when age was controlled for but, surprisingly, older mares initiated aggression less often than younger mares when size was controlled for. So increases in size may increase domination, while increases in age — assuming mares are finished growing — may decrease aggression.
- The more mares in a band, the more frequently a mare was involved in aggression.
- Subordinate mares who were nursing received more aggression than when they were not nursing. This suggests that competition between mares may involve interfering with the reproduction of other mares.
Size Matters — or Not. There are some studies that find that in social groups, the larger animals are more likely to be dominant — might makes right. Several studies have found this to be the case with horses43, but other studies have not found a relation between size and dominance.44 Size or weight may be more important than age near the top of the hierarchy, and age may be more important near the bottom.45
Residency. The new kid on the block is the likely target of the bully down the street. A horse that is new to a herd likely knows how that kid feels. After a time, newcomers gain acceptance, forming bonds and gaining social experience. They also gain comfort in the pasture, learning where the best spots are and how things work. The longer a horse stays in a group, the higher his or her rank.46
Social rank is a handy quality which avoids the need for scuffles over scarce resources. But in most situations, it is not important. In a large uncrowded pasture, you will see few manifestations of dominance or submission, and even fewer confrontations in which social rank is established or reinforced. What you will see plenty of is independent grazing, and grazing with friends.47 Horses have heeded the advice of “make love not war.”
Dominance has no biological counterpart. Dominance is a social status, developed through a set of behaviors. So while you might say that your horse is dominant, you mean that he is dominant in the hierarchy of his herd. Shuffle some other horses into the mix, and anything can happen. A big aggressive horse added to a herd can make a dominant horse submissive.
If you are here in this book, it might mean that you have the same chronic yearning that I have to understand what is “underneath”, or as someone has asked, “what is underneath underneath?” There are qualities we might explore that could lead to dominance, and that have a biological basis.
One such quality is our old friend “fight or flight”. A dominant horse is more willing to fight than a submissive horse; a submissive horse will be quicker to flee than a dominant horse. What triggers these tendencies?
Aggressiveness and Dominance
Many will tell you that aggressiveness underlies dominance: a horse that is aggressive is dominant, and one that is not aggressive will be of lower rank. Aggressiveness, here, could be defined as willingness to threaten and fight. The connection between dominance and aggressiveness is obvious, but it doesn’t seem to advance our understanding. Why do horses differ in aggressiveness?
Among stallions and geldings, it might be that testosterone levels are involved in aggressiveness or dominance. It is well known that animals who have a higher level of testosterone behave more aggressively and can even attack their brothers; they are more combative, more sexually active and bolder in claiming or searching for food.48 One study makes it clear that when a stallion emerged from his bachelor band to take on a harem, his testosterone level significantly rose, and remained high while he was with the harem. When this stallion was displaced from the harem and returned to the bachelor band, his testosterone level dropped.49 We don’t know what the baseline should be though: do the mares raise a stallion’s testosterone level, or the presence of bachelors lower it? There is certainly a great deal of research linking testosterone to aggression in a variety of species.
But research also suggests that testosterone may be necessary but not sufficient for aggression. Its level seems to increase when we win at chess or in some sport, and decrease when we lose. There is the suggestion that testosterone prepares the body to respond to competition or challenges to status, and it is certainly well known that testosterone makes both males and females bigger, stronger, and more energetic.50 Are there other hormones that help account for aggression?
Cortisol has been proposed as an “antagonist” for testosterone. The connection between testosterone and aggression in humans is reviewed in a recent paper: “Neuroimaging techniques in adult males have shown that testosterone activates the amygdala enhancing its emotional activity and its resistance to prefrontal restraining control. This effect is opposed by the action of cortisol which facilitates prefrontal area cognitive control on impulsive tendencies aroused in the subcortical structures… Testosterone activates the subcortical areas of the brain to produce aggression, while cortisol and serotonin act antagonistically with testosterone to reduce its effects.51”
In fact, where testosterone may underlie our “fight” response, cortisol may underlie the “flight” response.
Believing that testosterone increases aggressiveness, and cortisol reduces it, we shouldn’t be surprised to learn that the ratio of the levels of these two hormones is actually behind whether aggression will occur: if there is high testosterone to promote aggression, and low levels of cortisol to inhibit it, aggression will be more likely than if that high level of testosterone is inhibited by a high level of cortisol.52
The relationship between cortisol and dominance has been studied in rainbow trout. In an important experiment, two rainbow trout were matched for size and weight, and placed in a tank together. In short order, a fight for dominance would develop, and eventually one would win, and the other would retreat and try to hide from the winner. The winners and losers were allowed to interact for 5 minutes, 3 hours, or 24 hours before they were netted, anesthetized, decapitated, dissected (and perhaps eaten?). In a lengthy lab procedure, samples of each fish were analyzed for the concentration of cortisol. The researchers found that immediately (within 5 min) after the termination of staged fights for social dominance, a large increase in blood plasma cortisol was observed in both fight losers (future subordinate fish) and winners (future dominant fish). In dominant fish, cortisol then decreased rapidly (within 3 h) to the level of unstressed controls, while continuing to increase in subordinate fish. At 3 h following fights, the serotonin was activated in both dominant fish and subordinate fish. This effect was reversed in dominant individuals within 24 h of social interaction, whereas in subordinate fish serotonin was still high in all brain regions by 24 h. Similarly, a strong increase in brain cortisol was indicated after 24 h of social interaction in subordinate fish, but not in dominant fish.53 While more research might be needed to explore these effects in other species, it appears that cortisol and serotonin are increased in a fish that has lost a fight, and may remain high. Its role may be to prevent the loser from rejoining combat, and help maintain a lower rank. Other studies support the finding of higher cortisol levels in socially subordinate animals.54
Aggressiveness can be increased by raising testosterone or lowering cortisol. Dominant individuals may have a high ratio of testosterone to cortisol, whereas subordinate individuals may have a lower ratio. Scrambling for rank in a social group may fine-tune this ratio.
Self-Confidence and Dominance
Others might believe that self-confidence underlies dominance (and perhaps aggressiveness as well). A study by Joel Berger concluded “Indexes of nervousness (NER), calculated while horses were drinking, showed that stallions were less nervous than mares. A low NER was correlated with individuals leading toward drinking areas, whereas a high NER existed in individuals initiating flight although no single horse acted consistently as a leader.55” Nervousness is one side of a coin that has self-confidence on the other. This dimension might be important in understanding aggressive encounters, dominance, and other processes in a herd, but seems to be little studied.
When I look at my thoroughbred and my mule side by side, I see differences in many situations, and I can correctly guess how they’ll each behave when we come to a new situation. In a new situation, my mule is less fearful, more willing to explore the new object. At a creaky wooden bridge, my mule is willing to cross, while my horse would prefer to hang back. When he comes to a deep puddle in one of our walks, my mule willingly walks right through it, while my horse balks, and will choose to go around it, not getting his feet wet. When he comes upon some new horses in a pasture, my mule is eager to initiate play over the fence, while my horse would prefer to just nuzzle and sniff. When playing in the arena, my mule initiates, and plays hard and long until my horse escapes the game. In a confrontation, my mule is likely to move forward, my horse likely to back away. In all these cases, my mule seems more self-confident than my horse, more adventurous, more playful, less concerned for his own safety. Do confidence, adventurousness, playfulness, or other qualities underlie dominance, rather than aggressiveness?
Playfulness and Dominance
Suppose playfulness underlies (aggressiveness and) dominance: two young horses begin their play with differing size and skill. One will have been born a bit earlier than the other, and be a bit larger and more coordinated, so differ in basic play skills. They may also differ in how eager they are to play. As a result, one initiates play more often than the other. Play in most animals is mock fighting — it is not throwing a baseball or riding a bike. The playful horse will develop more skill in mock confrontations, and thus more skill in real ones. Along the way, he’ll develop more confidence in such situations. He may be more satisfied with the outcomes, which will encourage more such play. In the course of mock fighting, he will be increasingly likely to prevail. Later, as an adult, when there is a squabble over some resources, he is confident and competent. He uses some of those skills and attitudes he developed during play, and voilà! He prevails. A horse that is successful in play might be expected to become “dominant.”
A horse that grew up as the only colt or filly in the herd, or who was kept in a stall at a young age, will not have developed such skills in play, and won’t do as well in confrontations. Interactive play peaks at 3-4 months of age,56 but continues throughout life. Most race horses begin their careers at age two, and began preparing for those careers at an earlier age. During a race horse’s career, 23 hours a day are likely spent in a stall, and an hour a day spent running hard. In no hour of the day does a race horse get to play with peers. Without interaction and play with peers, social skills have little opportunity to develop. Without childhood play with peers, in my theory, a horse or human will not be very comfortable in aggressive encounters. Does this notion apply to those who are the only child?
And Underneath All of That?
In the section on Fear, Flight, Fight, Freeze, I wrote “The autonomic nervous system (ANS) is an unconscious control system found in all animals that regulates such things as heart rate, digestion, respiratory rate, and the fight-flight-freeze response. When triggered, the ANS quickly decides if we should fight, flee, or freeze. If fighting appears to be the best solution, the ANS triggers anger and aggressive behavior. If fleeing seems like a much better way to solve the problem, then flight is in order.” Perhaps the ANS evaluates the level of testosterone, cortisol, and other inputs when it makes its recommendation to the body.
1 image source: Ransom, Jason I., and Brian S. Cade. “Quantifying Equid Behavior–A Research Ethogram for Free-Roaming Feral Horses.” U.S. Geological Survey Techniques and Methods 2-A9, 23 p. (2009) http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1018&context=usgspubs
2 Bernstein, Irwin S. “Dominance: the baby and the bathwater.” Behavioral and brain sciences 4.03 (1981): 419-429.
3 For an excellent thorough discussion of the many meanings of dominance, see Drews, Carlos. “The concept and definition of dominance in animal behaviour.” Behaviour 125.3 (1993): 283-313.
4 Houpt, Katherine A., Karen Law, and Venera Martinisi. “Dominance hierarchies in domestic horses.” Applied Animal Ethology 4.3 (1978): 273-283.
5 Morell, Virginia. “Life at the top: animals pay the high price of dominance.” Science 271, no. 5247 (1996): 292-293.
6 Houpt, Katherine A., and Thomas R. Wolski. “Stability of equine hierarchies and the prevention of dominance related aggression.” Equine veterinary journal 12, no. 1 (1980): 15-18.
7 Goodwin, Deborah. “The importance of ethology in understanding the behaviour of the horse.” Equine Veterinary Journal 28 (1999): 15-19.;
Miller, Richard. “Male aggression, dominance and breeding behavior in Red Desert feral horses.” Ethology 57, no. 3‐4 (1981): 340-351.
8 Šárová, Radka, Marek Špinka, and José L. Arias Panamá. “Synchronization and leadership in switches between resting and activity in a beef cattle herd—a case study.” Applied Animal Behaviour Science 108, no. 3 (2007): 327-331.
9 Allee, W. C., M. N. Allee, and E. W. Castles. “Concerning leadership in a flock of white Pekin ducks.” Bull. ecol. Soc. of America 27 (1946): 15-16.
10 Scott, John Paul. “Social behavior, organization and leadership in a small flock of domestic sheep.” (1945).
11 Stewart, Jeannie C., and J. P. Scott. “Lack of correlation between leadership and dominance relationships in a herd of goats.” Journal of comparative and physiological psychology 40, no. 4 (1947): 255.
12 Reinhardt, Viktor. “Movement orders and leadership in a semi-wild cattle herd.” Behaviour 83.3 (1983): 251-264.
13 Tulloh 1961; Kondo et al 1980 dietrich et al 1965 rathore 1982 benham 1982
14 Dove et al 1974; Arnold 1977
15 Escós, J., C. L. Alados, and J. Boza. “Leadership in a domestic goat herd.” Applied Animal Behaviour Science 38.1 (1993): 41-47.
16 Meese, G. B., and R. Ewbank. “Exploratory behaviour and leadership in the domesticated pig.” The British veterinary journal 129.3 (1973): 251-259.
17 Tulloh, N. M. “Behaviour of cattle in yards. I. Weighing order and behaviour before entering scales.” Animal Behaviour 9.1-2 (1961): 20-24.
18 Dumont, B., A. Boissy, C. Achard, A. M. Sibbald, and H. W. Erhard. “Consistency of animal order in spontaneous group movements allows the measurement of leadership in a group of grazing heifers.” Applied Animal Behaviour Science 95, no. 1 (2005): 55-66.
19 Schulte, Norbert, and Hans Klingel. “Herd structure, leadership, dominance and site attachment of the camel, Camelus dromedarius.” Behaviour 118.1 (1991): 103-114.
20 Escós, J., C. L. Alados, and J. Boza. “Leadership in a domestic goat herd.” Applied Animal Behaviour Science 38, no. 1 (1993): 41-47
21 Šárová, Radka, Marek Špinka, José L. Arias Panamá, and Petr Šimeček. “Graded leadership by dominant animals in a herd of female beef cattle on pasture.” Animal Behaviour 79, no. 5 (2010): 1037-1045.
22 Berger, Joel. “Organizational systems and dominance in feral horses in the Grand Canyon.” Behavioral Ecology and Sociobiology 2, no. 2 (1977): 131-146.
23 Reinhardt, Viktor. “Movement orders and leadership in a semi-wild cattle herd.” Behaviour 83, no. 3 (1983): 251-264.
24 Darling, F. F.: A herd of red deer: a study in animal behavior. London: Oxford University Press, 1937.
25 Meese, G. B., and R. Ewbank. “Exploratory behaviour and leadership in the domesticated pig.” The British veterinary journal 129.3 (1973): 251-259.
26 Berger, Joel. “Organizational systems and dominance in feral horses in the Grand Canyon.” Behavioral Ecology and Sociobiology 2, no. 2 (1977): 131-146.
27 McHugh, T.: Social behavior in the American buffalo (Bison bison bison). Zoologica 43, 1-37 (1958)
28 Sato, Syusuke. “Leadership during actual grazing in a small herd of cattle.” Applied Animal Ethology 8, no. 1-2 (1982): 53-65.
29 McHugh, T.: Social behavior in the American buffalo (Bison bison bison). Zoologica 43, 1-37 (1958)
30 Fraser, Andrew F. The behaviour of the horse. CAB international, 1992.; Goodwin, Deborah. “The importance of ethology in understanding the behaviour of the horse.” Equine Veterinary Journal 28 (1999): 15-19.
31 Montgomery, Gerald Gene. “Some aspects of the sociality of the domestic horse.” Transactions of the Kansas Academy of Science (1903-) 60.4 (1957): 419-424.
32 Houpt, Katherine A., Karen Law, and Venera Martinisi. “Dominance hierarchies in domestic horses.” Applied Animal Ethology 4, no. 3 (1978): 273-283.
33 Houpt, Katherine A., and Thomas R. Wolski. “Stability of equine hierarchies and the prevention of dominance related aggression.” Equine veterinary journal 12, no. 1 (1980): 15-18.
34 Sigurjónsdóttir, H., M. C. van Dierendock, and A. G. Thórhallsdóttir. “Friendship among horses—Rank and kinship matter.” Havemeyer Foundation workshop on horse behavior. 2002.
35 Fureix C, Bourjade M, Henry S, Sankey C, Hausberger M (2012) Exploring aggression regulation in managed groups of horses Equus caballus. Appl Anim Behav Sci 138: 216–228.; see also Sigurjónsdóttir, H., M. C. van Dierendock, and A. G. Thórhallsdóttir. “Friendship among horses—Rank and kinship matter.” Havemeyer Foundation workshop on horse behavior. 2002. These authors write “That has also been documented for other groups, both feral and domestic (Keiper and Sambraus,1986; Rutberg and Greenberg, 1990; van Dierendonck et al, 1995) and the Przewalski horse (Feh, 1988; Keiper and Receveur, 1992) while other studies on the domestic horse have not shown a significant correlation (Houpt et al, 1978; Houpt and Keiper, 1982) although adults were dominant over juveniles. ”
36 Houpt, Katherine A., Karen Law, and Venera Martinisi. “Dominance hierarchies in domestic horses.” Applied Animal Ethology 4.3 (1978): 273-283.
37 Scott, J.P., 1948. Dominance and frustration aggression hypothesis. Physiol. Zool., 21:31-39.
38 Schein, M.W. and Fohrman, M.H., 1955. Social dominance relationships in a herd of dairy cattle. Br. J. Anim. Behav., 3: 45-55.
39 For a sampling of studies showing that dominance increases with age in various species, see Allen, Douglas S., and Wayne P. Aspey. “Determinants of social dominance in eastern gray squirrels (Sciurus carolinensis): a quantitative assessment.” Animal Behaviour 34 (1986): 81-89.; Arcese, P., and J. N. M. Smith. “Phenotypic correlates and ecological consequences of dominance in song sparrows.” The Journal of Animal Ecology (1985): 817-830.; Holberton, Rebecca L., Ralph Hanano, and Kenneth P. Able. “Age-related dominance in male dark-eyed juncos: effects of plumage and prior residence.” Animal Behaviour 40, no. 3 (1990): 573-579.; Jennings, Dómhnall J., Caitríona M. Carlin, Thomas J. Hayden, and Martin P. Gammell. “Investment in fighting in relation to body condition, age and dominance rank in the male fallow deer, Dama dama.” Animal Behaviour 79, no. 6 (2010): 1293-1300.; Owen-Smith, Norman. “Age, size, dominance and reproduction among male kudus: mating enhancement by attrition of rivals.” Behavioral Ecology and Sociobiology 32, no. 3 (1993): 177-184.
40 Feist, J.D. and McCullough, D.R., 1976. Behavior patterns and communication in feral horses. Z. Tierpsychol., 41: 337-371.; Tyler, S.J., 1972. The behaviour and social organization of the New Forest ponies. Anim. Behav. Monog., 5: 85-196.
41 Pelligrini, S.W., 1971. Home range territoriality and movement patterns of wild horses in the Wassuk Range of western Nevada. Masters Thesis, University of Nevada.
42 Rutberg, Allen T., and Stacey A. Greenberg. “Dominance, aggression frequencies and modes of aggressive competition in feral pony mares.” Animal Behaviour 40, no. 2 (1990): 322-331.
43 Montgomery, Gerald Gene. “Some aspects of the sociality of the domestic horse.” Transactions of the Kansas Academy of Science (1903-) 60.4 (1957): 419-424.; Grzimek, Bernhard. “Rangordnungsversuche mit pferden.” Zeitschrift für Tierpsychologie 6.3 (1949): 455-464.
44 Berger, Joel. “Organizational systems and dominance in feral horses in the Grand Canyon.” Behavioral Ecology and Sociobiology 2, no. 2 (1977): 131-146.
45 Tyler, Stephanie J. “The behaviour and social organization of the New Forest ponies.” Animal Behaviour Monographs 5 (1972): 87-196.
46 Clutton-Brock et al, 1976 and van Dierendonck et al, 1995 cited in Sigurjónsdóttir, H., M. C. van Dierendock, and A. G. Thórhallsdóttir. “Friendship among horses—Rank and kinship matter.” Havemeyer Foundation workshop on horse behavior. 2002.
47 Arnold, G. W., and A. Grassia. “Ethogram of agonistic behaviour for thoroughbred horses.” Applied Animal Ethology 8, no. 1-2 (1982): 5-25.
48 For example, see Müller M.S., Moe B., Groothius T.G.G. Testosterone increases siblicidal aggression in black-legged kittiwake chicks (Rissa tridactyla) // Behavioral Ecology and Sociobiology. Vol. 68, Issue 2. February 2014. P. 223-232.
49 McDonnell, Sue M., and Samantha C. Murray. “Bachelor and harem stallion behavior and endocrinology.” Biol Reprod Mono 1 (1995): 577-590.
50 Mims, Christopher. “Strange but True: Testosterone Alone Does Not Cause Violence Hormones don’t necessarily make men violent, but they do cause them to seek social dominance” Scientific American July 5, 2007 https://www.scientificamerican.com/article/strange-but-true-testosterone-alone-doesnt-cause-violence/
51 Batrinos, Menelaos L. “Testosterone and aggressive behavior in man.” International journal of endocrinology and metabolism 10.3 (2012): 563-568.
52 Dabbs, J., Jurkovic, G. J., & Frady, R. L. (1991). Salivary testosterone and cortisol among late adolescent offenders. Journal of Abnormal Child Psychology, 19(4), 469–478.; Glenn, A., Raine, A., Schug, R. A., Gao, Y., & Granger, D. A. (2011). Increased testosterone-to-cortisol ratio in psychopathy. Journal of Abnormal Psychology, 120(2), 389–399.; Mehta, P. H., Jones, A. C., & Josephs, R. A. (2008). The social endocrinology of dominance: Basal testosterone predicts cortisol changes and behavior following victory and defeat. Journal of Personality and Social Psychology, 94(6), 1078–1093.; Mehta, P. H., & Josephs, R. A. (2010). Testosterone and cortisol jointly regulate dominance: Evidence for a dual-hormone hypothesis. Hormones and Behavior, 58(5), 898–906.; Pajer, K., Tabbah, R., Gardner, W., Rubin, R., Kennethczambel, R., & Wang, Y. (2006). Adrenal androgen and gonadal hormone levels in adolescent girls with conduct disorder. Psychoneuroendocrinology, 31(10), 1245–1256.; Popma, A., Vermeiren, R., Geluk, C., Rinne, T., Vandenbrink, W., Knol, D., et al. (2007). Cortisol moderates the relationship between testosterone and aggression in delinquent male adolescents. Biological Psychiatry, 61(3), 405–411.; Terburg, D., Morgan, B., & van Honk, J. (2009). The testosterone–cortisol ratio: A hormonal marker for proneness to social aggression. International Journal of Law and Psychiatry, 32(4), 216–223.; van Honk, J., Harmon-Jones, E., Morgan, B. E., & Schutter, D. J. L. G. (2010). Socially explosive minds: The triple imbalance hypothesis of reactive aggression. Journal of Personality, 78(1), 67–94.
53 Øverli, Øyvind, Charmaine A. Harris, and Svante Winberg. “Short-term effects of fights for social dominance and the establishment of dominant-subordinate relationships on brain monoamines and cortisol in rainbow trout.” Brain, Behavior and Evolution 54, no. 5 (2000): 263-275.
54 Ejike, C., and C.B. Schreck (1980) Stress and social hierarchy rank in coho salmon. Trans. Am. Fish. Soc., 109: 423–426.; Golub, M., E. Sassenrath, and G. Goo (1979) Plasma cortisol levels and dominance in peer groups of rhesus monkey weanlings. Horm. Behav., 12: 50–59.; McLeod, P.J., W.H. Moger, J. Ryon, S. Gadois, and J.C. Fentress (1996) The relation between urinary cortisol levels and social behaviour in captive timber wolves. Can. J. Zool., 74: 209–216.; Sapolsky, R.M. (1990) Adrenocortical function, social rank, and personality among wild baboons. Biol. Psych., 28: 862–878.; Winberg, S., and O. Lepage (1998) Elevation of brain 5-HT activity, POMC expression, and plasma cortisol in socially subordinate rainbow trout. Am. J. Physiol., 43: R645–R654.
55 Berger, Joel. “Organizational systems and dominance in feral horses in the Grand Canyon.” Behavioral Ecology and Sociobiology 2, no. 2 (1977): 131-146.
56 Overall, Karen L. “Normal Social Behavior in Horses”. Merck Veterinary Manual. http://www.merckvetmanual.com/horse-owners/behavior-of-horses/normal-social-behavior-in-horses