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Fighting

Last revised April 15, 2017.

Boxing and dancing between these two stallions is the highest level of agonism that feral horses typically express.1

Agonistic behavior is a group of social behaviors that relate to fighting. Agonistic behavior may include warnings (threats and displays), efforts to break off an unpleasant encounter (retreats, placation), fighting, and conciliation. Aggression is a subset of agonistic behavior. The word labels hostile or violent behavior, and may include threats of such behavior, but excludes retreats, placation, and conciliation. Aggression is much more common in captive domestic horses than in feral horse bands.2

Aggressiveness is a temperament in which a horse shows hostile or violent behavior toward a human, horse, or other animal. Aggressive horses are more likely to show threat displays under the right circumstances. In contrast, an assertive horse is confident and forceful. An assertive horse might be the first through the gate at feeding time; an aggressive horse might be more likely to bite another horse while waiting at the gate. A horse may be both assertive and aggressive.

Most animals get angry from time to time, show aggressiveness, and will fight if provoked. It is not likely that any species other than Homo sapiens enjoys fighting, and most do what they can to avoid it. Fighting is avoided, when possible, because it may lead to injury in both combatants.

A “threat display” is one good means to achieve this: by showing a set of agreed-upon signals, the would-be combatants have a chance to size each other up, and one or both have a chance to withdraw. Across many mammal species, threat displays share many elements:

  • Behaviors which improve the perception of the opponent: facing the opponent, opening both eyes, flaring the nostrils (and possibly snorting, which clears the nostrils, likely improves the sense of smell, and can make a mess on the floor).
  • Behaviors which may minimize damage to the face, including pinning ears back and partially closing eyes;
  • Behaviors which expose the available weapons, including readying claws and opening jaws wide, and baring teeth;
  • Behaviors which improve the effectiveness of a bite, such as lowering the head — which protects the neck and positions the head closer to the neck of the opponent.

Most of these behaviors are involved in the threat displays of all mammals, which suggests that the basic set of behaviors evolved long, long ago near the dawn of proto-mammals. But many of these behaviors can be found in very different species, such as snapping turtles and birds (facing the opponent, opening both eyes, opening jaws wide, lowering the head), so such behaviors may date back to when turtles and birds came along.

Threat display in a mammal.3

In horses, aggressive threats usually follow a sequence of pinning the ears back, then pulling back lips and showing teeth, then flaring nostrils, then lowering neck and head into a snowplow shape, then advancing toward target.

Angry horse. Before this bite, this horse had pinned his ears back, pulled back his lips and showed his teeth, flared his nostrils, lowered his head, and advanced to his target.4 He retains that threatening posture as he separates this biker’s hand from his arm.

A confrontation between two horses begins when they approach each other. When they are close enough, such as when two horses are meeting over a fence, they will likely sniff each other. One may squeal. And then there may be physical contact, which sometimes includes experimental bites of one by the other.

Each of these behaviors seems optional. In many cases, there is no sniffing and/or no squealing and/or no physical contact. In over half of the confrontations examined in one study,5 there was no sniff, no squeal, no physical contact — one of the two horses simply withdrew.

Is aggressiveness a legitimate personality dimension? Is it stable in a horse across time and place, and do different horses demonstrate different levels of it?

We need some research on horses to answer these questions. While we wait for that research, let us consider piglets. Researchers in the Netherlands and Denmark6 were interested in whether aggressiveness in piglets constitutes an aspect of personality. They took one week old piglets and put them in a cage with others for 30 minutes, during which time they recorded threat, head knock, biting, fighting, and chasing. They defined aggressiveness as the sum of the frequencies of these 6 behaviors in that 30 minute period. In addition, two observers classified each piglet as aggressive or non-aggressive based on their qualitative impression. This procedure was repeated a week later, when the piglets were now two weeks old. In addition to this assessment of aggressiveness, the researchers explored “resistance” by holding each piglet on his back for 60 seconds, with one hand placed loosely over the head. In each of five such “back tests”, piglets were scored as non-resistant if they made fewer than two escape tests, or resistant if they made three or more escape attempts. Sounds like MMA, doesn’t it?

The researchers found that those piglets who they had scored as “resistant” were also likely to have been scored as “aggressive”. The researchers concluded that “This association in behaviour and its consistency over time strongly suggests the existence of behavioural strategies to cope with conflict situations that are typical of individual pigs and are measurable already in the very first weeks of their life.”

From Threat to Fight

Fighting in horses develops in a standard sequence of behaviors. The standardization of confrontations allows both contestants to know the level that things have escalated to, and gives them both an opportunity to back off, if they don’t wish to go farther. A horse will not simply walk over to another and start a fight. Imagine a pyramid of behaviors. The pyramid is built on threat; the threats escalate as we move up the pyramid, and fighting only happens at the very top. The pyramid describes how common each stage is. Most conflicts terminate at the bottom layers.

The earliest stage of aggression is built on arched neck threats, sometimes accompanied by parallel prancing and by pawing, and usually accompanied by ears pinned back. Often the arched neck is part of a ritual which includes sniffing each other at the shoulder or crotch.7 All of these behaviors allow a stallion to demonstrate his size and fitness, to learn more about his potential opponent, and to learn more about his opponent’s identity. About 80% of all aggressive encounters between stallions break off after this stage8, and most encounters between feral horse stallions end in a draw.9 The stallions in the next photo demonstrate the arched necks.

Agonism is expressed by both of these feral horses in the form of a threat. This is the most common form of agonism between feral horses and is most easily recognized by the laterally positioned, posterior pointing direction of the ears (shown in both animals here)10.

 

Pushing is an agonistic expression shown here by the horse in the foreground pushing toward the other horse.11

 

Chasing is a moderately intense form of agonism and is shown here along with an expression of imminent biting behavior.12

 

Biting is a common expression of agonism in equids and is expressed here between feral horse females to assert dominance.13 Junior in the foreground observes her mom take a pounding.

 

Rearing is an expression often signifying a potentially intense agonistic interaction, typically between feral stallions.14

 

Striking or stomping is highly agonistic. It is being expressed by the feral stallion on the left by the directed extension and downward motion of his front feet.15

 

 

Injuries

Fighting is rare in feral horses, more common in domestic horses. In feral horses, there are normally stable dominance hierarchies, and relationships have been worked out. Herd composition may change frequently in domestic horses, and with each newcomer or each horse removed from the herd, the dominance hierarchy needs review. Aggressive behavior is most common and intense when a herd is not stable16, and a well-established dominance hierarchy is critical to avoiding injury.17 In addition, crowding contributes to fighting. Not only does it artificially add to the tension between horses, but it may prevent a horse who is willing to submit from getting out of the way of a dominant horse.

Fighting leads to injuries, and injuries can be serious. A horse’s two weapons are biting and kicking. Biting is most often used in offense, while kicking is most often a defensive weapon.18

Biting may be the more common manifestation of aggression,19 but kicks appear to be the most common cause of serious injuries. In a study of 1,181 injuries, Derungs and other researchers20 determined that most injuries from fighting come from kicks, and they are serious: 47% of these injuries resulted in bone fracture, and in 13% of injuries from fighting, euthanasia was required. The radius and tibia seem especially vulnerable to kick injuries, especially when the injury is to the back side of the bone.21 Often the injury from a kick is a fissure fracture which immediately produces lameness but in the next few weeks may result in a complete fracture.22

Fighting is not the only cause of kick injuries. Sometimes exuberance or play includes mild kicks that have serious consequences.

Kicks may have lesser consequences if the kicking horse is not wearing shoes on his hind feet.23 Because aggression is most likely when adding a new horse to a herd, removing the back shoes of the new horse may reduce the chance that he will seriously injure another in the established herd.

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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 Houpt, Katherine Albro, and Ronald Keiper. “The position of the stallion in the equine dominance hierarchy of feral and domestic ponies.” Journal of Animal Science 54, no. 5 (1982): 945-950.

3 Image source: https://www.flickr.com/photos/superwebdeveloper/4302203471

4 Image source: http://i.imgur.com/P0Gr3Bx.jpg

5 Rubenstein, Daniel I., and Mace A. Hack. “Horse signals: the sounds and scents of fury.” Evolutionary Ecology 6.3 (1992): 254-260.

6 Hessing, Manfred JC, A. Mette Hagelsø, J. A. M. Van Beek, R. P. Wiepkema, W. G. P. Schouten, and R. Krukow. “Individual behavioural characteristics in pigs.” Applied Animal Behaviour Science 37, no. 4 (1993): 285-295.

7 Miller, Richard. “Male aggression, dominance and breeding behavior in Red Desert feral horses.” Ethology 57, no. 3‐4 (1981): 340-351.

8 Miller, Richard. “Male aggression, dominance and breeding behavior in Red Desert feral horses.” Ethology 57, no. 3‐4 (1981): 340-351.

9 Feist, James D., and Dale R. McCullough. “Behavior patterns and communication in feral horses.” Ethology 41, no. 4 (1976): 337-371.

10 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

11 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

12 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

13 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

14 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

15 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

16 Arnold, G.W. and Grassia, A. (1982) Ethogram of agonistic behavior for Thoroughbred horses. Appl. Anim. Ethol. 8, 5-25.; Grogan, E.H. and McDonnell, S.M. (2005) Injuries and blemishes in a semi-feral herd of ponies. J. equine vet. Sci. 25, 26-30.; Houpt, K.A. (1991) Investigating equine ingestive, maternal, and sexual behavior in the field and in the laboratory. J. anim. Sci. 69, 4161-4166.; Houpt, K.A. and Keiper, R. (1982) The position of the stallion in the equine dominance hierarchy of feral and domestic ponies. J. anim. Sci. 54, 945-950.; van Dierendonck, M.C., Sigurjónsdóttir, H., Colenbrander, B. and Thorhallsdóttir, A.G. (2004) Differences in social behaviour between late pregnant, post-partum and barren mares in a herd of Icelandic horses. Appl. anim. behav. Sci. 89, 283-297.; Grogan and McDonnell 2005

17 McGreevy, P. (2004) Social behavior. In: Equine Behavior: A Guide for Veterinarians and Equine Scientists. Ed: P. McGreevy, W.B. Saunders Co., Edinburgh. pp 119-150.; Mills, D. and Nankervis, K. (1999) Equine Behaviour: Principles & Practice, Eds: D. Mills and K. Nankervis, Blackwell Science, Oxford. pp 110-137.

18 Waring, G.H. (2003) Agonistic behavior. In: Horse Behavior, 2nd edn., Ed: G.H. Waring, Noyes Publications/William Andrew Publishing, Norwich, New York. pp 253-269.; Wells, S.M. and von Goldschmidt-Rothschild, B. (1979) Social behaviour and relationships in a herd of Camargue horses. Z. Tierpsychol. 49, 363-380.

19 Keiper, R. and Receveur, H. (1992) Social interactions of free-ranging Przewalski horses in semi-reserves in the Netherlands. Appl. anim. behav. Sci. 33, 303-318.

20 Derungs, S. B., A. E. Furst, M. Hassig, and J. A. Auer. “Frequency, consequences and clinical outcome of kick injuries in horses: 256 cases (1992-2000).” Wiener Tierarztliche Monatsschrift 91, no. 5 (2004): 114-119. Cited in Knubben, J. M., A. Fürst, L. Gygax, and M. Stauffacher. “Bite and kick injuries in horses: Prevalence, risk factors and prevention.” Equine veterinary journal 40, no. 3 (2008): 219-223.

21 Struchen, C. (1992) Untersuchung der Anwendbarkeit von drei verschiedenen Frakturklassifikations-systemen bei Frakturen der langen Röhrenknochen des Pferdes. Vet. Med. Diss., University Zurich. Cited in Derungs, S., A. Fuerst, C. Haas, U. Geissbühler, and J. A. Auer. “Fissure fractures of the radius and tibia in 23 horses: a retrospective study.” Equine Veterinary Education 13, no. 6 (2001): 313-318.

22 Derungs, S., A. Fuerst, C. Haas, U. Geissbühler, and J. A. Auer. “Fissure fractures of the radius and tibia in 23 horses: a retrospective study.” Equine Veterinary Education 13, no. 6 (2001): 313-318.

23 Piskoty, G., Jäggin, S., Michel, S.A. and Fürst, A. (2005) Experimental study of fractures of long bones due to impact loading. In: First International Conference

on Mechanics of Micromaterials & Tissues, Rob O. Ritchie, Waikoloa, Hawaii. p O21.

 

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