Fear, Flight, Fight, Freeze

Last revised April 18, 2017.

A horse responds to a black lab.1

Flight, Fight, or Freeze

Pain doesn’t merely affect a few nerves. It affects the entire nervous system. 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. But if neither will do — perhaps because we are in the jaws of the tiger, we may go limp. This freeze response,2 it turns out, is often the best way to avoid further injury from a predator.

I’ve listed these responses in their order of likelihood: among humans, “animals” might go to a bar looking for a fight, but in nature, animals do what they can to avoid injury, and avoid a fight. Predators only choose prey that they believe they can subdue without getting injured themselves. And they will break off an attack if they find they’ve misjudged the capabilities of their quarry.

Your horse’s desire to flee a dangerous situation is no different than yours. He and you differ only in what you judge to be dangerous. So we might be wiser if we were to say “flight or fight” rather than “fight or flight”. But that leaves out freezing, which is our last best hope for survival. If we cannot escape and cannot win a fight to the death, freezing may come to our rescue. Horses are flight animals. Fight animals. Freeze animals. They will do what it takes to stay alive. That makes them just like all other animals, including us.

And while we are at it, let’s look at some of the dumb claims that are floating around about prey animals. If you search for “horse is a prey animal”, Google will find nearly 50,000 pages expressing this novel view. But if you look for “cow is a prey animal”, you’ll only get about 10 hits. Does this mean that predators prefer to dine on horses? Or have horse people been dutifully repeating what they’ve heard, assuming that the rest of us can’t hear, read, or think? The amplifications of this deep insight are not illuminating:

  • Consider this: “The horse has a very fast response time. A prey animal must react instantly to a perceived predator to be able to survive.3” Whoa! If horses are so quick, wouldn’t a predator have to be quick to catch one?
  • And this: “Since they are a prey species, they must be able to detect predators.4” Whoa again! If horses need to be so adept at detecting predators, don’t predators need to be adept at detecting prey? Otherwise, what do they have for dinner?
  • And this: “Horses don’t reason whether an animal or object is a predator or not. Natural selection has made horses take fright first and think later, because that’s always been their most efficient way of survival.5” Whoa! Again. Take fright first?

I could find no useful surveys of factors in horse mortality, but the literature points to many causes of death in feral horses: violent rainstorms,6 emerging infectious disease,7 parasites,8 injury,9 inbreeding,10 fescue toxicosis,11 male sexual harassment,12 and so on. In some areas, predators take a toll on foals,13 but they do not seem able to take down adult horses. And as mountain lions disappear, horses gain ground.14 The horse had to evolve to deal with many troubles, ranging from occasional drought to finding the best dinner. They had to extract energy from coarse grasses, using a digestive system that is not as efficient as a rabbit or cow’s. Dealing with predators was on their to-do list, but it wasn’t the only concern a horse has ever had.

Wolves, bears, and mountain lions — all frequently cited as the predators who dine on horses — are even more skittish than your horse is when you approach. We haven’t domesticated them yet, and shouldn’t be surprised by their flightiness. Many of the animals in the woods around my house — deer, squirrels, raccoons, frogs — are both predators and prey animals15. I’ve been kind to them, and although wild, they don’t bolt when I approach. Wild animals are normally flighty; both predators and prey animals can become pretty tame. Your horse was only recently domesticated, and in some ways is still wild. His flightiness is more a result of this wildness than any notion that he is a prey animal.

Horses are Fight Animals

The convention in the horse literature is to say that “horses are flight animals”, and Google reports about 12,000 pages making this claim. Google shows only 4 pages claiming that “horses are fight animals”, and in all four cases, the authors seem to have omitted the “l” by accident. But such claims are oversimplifications.

Horses will fight. You’ve seen it in your pasture, and Google will show you hundreds of pictures of them fighting.16

When horses fight, they surely feel anger.

Humans sometimes feel anger at their horses, and begin a one-way fight. Yelling reveals our emotion but is an alien concept for horses. When a horse gets angry, he doesn’t yell. He doesn’t say anything. If you want your horse to know that you are angry, you won’t convey this with yelling. Or pummeling. Or yanking the reins. Or spurring it. Or beating it with a crop. Because horses rarely do anything that makes other horses angry, I think they may have trouble understanding anger — especially when they don’t understand what you were asking of them in the first place. Remember that horses can hear so much better than we do. If you have something to say to Mr. Horse, whisper it. But remember that because horses are non-verbal, your horse likely has no clue what you are saying, no matter how you say it.

Knowledge of how horses fight is of use if you are going to invade their space or annoy them. Joel Berger provides a great report on his study of feral horses in the Grand Canyon.17 Among his findings is a summary of the aggressive repertoire used to maintain intraband drink hierarchies. This information is particularly handy if you plan to go to a bar with your horse…

At the earliest stage of confrontation — pre-threat — a horse might do one or more of three things:

  • Body turn: shifting the rump in the direction of a conspecific;
  • Head bob: movement of the head in an upward and downward motion toward a conspecific;
  • Block: lateral movement of the body to force an intruder to another position by mild contact.

If pre-threat doesn’t work, the horse shifts to threat level of signals, including:

  • Rear leg lift: movement of a rear leg off the ground to a position preceding a kick;
  • Ears cocked, head lowered: simultaneous lowering of the head and neck, while cocking the ears;
  • Bite attempt: extension- of head and neck toward a conspecific followed by an unsuccessful attempt to bite.

In the rare case that a threat is ignored, the horse may resort to physical contact:

  • Rear leg kick: kicking a conspecific using one or both rear legs;
  • Front leg kick: kicking a conspecific with a front hoof;
  • Bite: biting a conspecific.

If you are going to do something that annoys your horse (like grooming him when he is trying to eat), keep your eyes open for signs of pre-threat. Stop immediately if he escalates to threat.

When fights occur in horses, it is likely that limited resources are involved. For instance, Berger suspects that drought conditions resulted in increased contact between feral bands of horses in his study, causing more fights.18

Fighting in feral horses is much less likely than in domestic horses, I believe. All horses would prefer not to fight, and when they are not confined, horses are free to move away from an antagonist, and cede the resource to them. In a confined pasture, no horse has the possibility of escape, and proximity may lead to provocation.

In the Jaws of Death

In the death grip of a mountain lion, a horse may freeze. A high level of pain, terror, or blood loss often triggers shock, which must underlie the freeze response. In shock, Wikipedia tells us, there is low blood pressure, rapid heart rate, a weak pulse, signs of poor end-organ perfusion (i.e.: low urine output, confusion, or loss of consciousness). The condition reduces blood loss and makes the victim less interesting to the attacker. YouTube is loaded with videos of grazing animals seeming to give up when in the jaws of a big cat. In some of these videos, the attacker becomes distracted, and the victim leaps up and runs off. Freeze is not a dumb idea, especially when flight or fight won’t work.

You may not be able to imagine being in the jaws of a lion or tiger. If you can, you probably can’t imagine going limp and waiting for it to lose interest in you. Joanna Greenfield can, though. She was feeding and trying to comfort a caged hyena when it attacked, mutilating her arm and then leg. She writes that she became a passive observer to the scene, watching the hyena tear into her but not feeling the expected pain. She was conscious, she was surely in shock, and she was involuntarily demonstrating the freeze response. She lived.

Ms. Greenfield: “The mind, I found is strange. It shut off during the attack, while my body continued to act, without thought or sight. I don’t remember him sinking his teeth into my arm, though I heard a little grating noise as his teeth chewed into the bone… I think it was then that he took the first piece from my arm and swallowed it without breathing, because a terror of movement settled in me at that moment and lasted for months. He moved up the arm… It didn’t hurt. It never did… My arm felt light and shrunken, as if half of it were gone, but I didn’t look… He came around behind me and grabbed my right leg, and again there was no pain — just the feeling that he and I were playing tug-of-war with my body — but I was afraid to pull too hard on the leg… In three moves I didn’t feel, he took out most of the calf… [A nearby worker] ran up and grabbed my good left arm, hustling me forward. Not so fast, I wanted to say, but I didn’t. Every step felt more wrong, and I dragged back against moving until he almost shoved me forward… We waited awhile, and then she gave me anti-shock injections. “I’m not in shock,” I said, and meant it.” Read her story in the New Yorker.19

Ms. Greenfield tells us some important things about shock and the freeze response. We learn that, at least in this case, sudden, massive tissue damage can occur without pain and without loss of consciousness or cognitive processing. We learn that fear of movement underlies the freeze response — “a terror of movement”, “but I was afraid to pull too hard on the leg”, “not so fast”, “every step felt wrong”. How much I want to believe that when a hyena eats its prey alive, that the prey watches but does not feel. I am grateful to Ms. Greenfield for telling us what we never want to learn firsthand.

If Ms. Greenfield had been this hyena’s prey in the wild, she would have quickly died of her injuries if she had not been consumed, and the freeze response would have been of no benefit. But there are many times when a predator seizes prey, prey goes limp, predator loses interest and leaves the scene, and unharmed prey bounds off.20 Don’t try this at home.

Ms. Greenfield is not the only one who managed to freeze in the jaws of death. You may know about opossums that “play dead” in the jaws of a dog or hands of a human. Sharks and rays do it when they are turned upside down.21 Chickens sometimes do it when their head is held to the ground. Other animals have also been reported to play dead, including trout, snakes, mice,22 gerbils,23 rats,24 rabbits25 and pigs.26 In most cases, these animals can be induced to play dead by placing them in the sort of position they would experience if being attacked by a predator, and holding them there. Playing dead has fancier names: tonic immobility or thanatosis.


1 Image source:

2 The freeze response is sometimes called the tonic “immobility reflex”, “animal hypnosis”, or “death feigning”. It is similar to REM sleep: both are controlled by the brain stem and have comparable paralysis, hypocampal theta rhythms, and thermoregulatory changes. See “Rapid eye movement sleep” in Wikipedia.

3 Williams, Carey A. “The Basics of Equine Behavior.” Jul 22, 2004.

4 Williams, Carey A. “The Basics of Equine Behavior.” Jul 22, 2004.

5 Davies, Neil. “The horse as a ‘prey’ animal.” Sep 28, 2014.

6 Scorolli, Alberto L., Andrea C. Lopez Cazorla, and Lidia A. Tejera. “Unusual mass mortality of feral horses during a violent rainstorm in Parque Provincial Tornquist, Argentina.” Mastozoología neotropical 13, no. 2 (2006): 255-258.

7 Daszak, Peter, Andrew A. Cunningham, and Alex D. Hyatt. “Emerging infectious diseases of wildlife–threats to biodiversity and human health.” science 287, no. 5452 (2000): 443.

8 Gaillard, J-M., M. Festa-Bianchet, N. G. Yoccoz, A. Loison, and C. Toigo. “Temporal variation in fitness components and population dynamics of large herbivores.” Annual Review of ecology and Systematics 31, no. 1 (2000): 367-393.

9 Boyd, Lee, and Ronald Keiper. “Behavioural ecology of feral horses.” The domestic Horse, the Evolution, Development and Management of Its Behaviour. Cambridge University Press, Cambridge (2005): 55-82.

10 Gaillard, J-M., M. Festa-Bianchet, N. G. Yoccoz, A. Loison, and C. Toigo. “Temporal variation in fitness components and population dynamics of large herbivores.” Annual Review of ecology and Systematics 31, no. 1 (2000): 367-393.

11 Goodloe, Robin B., Robert J. Warren, David A. Osborn, and Cynthia Hall. “Population characteristics of feral horses on Cumberland Island, Georgia and their management implications.” The Journal of wildlife management (2000): 114-121.

12 Reale, Denis, Patrick Bousses, and Jean-Louis Chapuis. “Female-biased mortality induced by male sexual harassment in a feral sheep population.” Canadian Journal of Zoology 74, no. 10 (1996): 1812-1818.

13 Turner Jr, John W., Michael L. Wolfe, and Jay F. Kirkpatrick. “Seasonal mountain lion predation on a feral horse population.” Canadian Journal of Zoology 70, no. 5 (1992): 929-934.; Turner Jr, John W., and Michael L. Morrison. “Influence of predation by mountain lions on numbers and survivorship of a feral horse population.” The Southwestern Naturalist (2001): 183-190.

14 Turner Jr, John W., and Michael L. Morrison. “Influence of predation by mountain lions on numbers and survivorship of a feral horse population.” The Southwestern Naturalist (2001): 183-190.

15 Squirrels are both predator (sometimes eating baby birds in the nest, for instance) as well as prey (regularly eaten by foxes and hawks). Raccoons are both predator (eating frogs, crayfish, alligator hatchlings, and anything they can catch) as well as prey (killed by dogs and men with dogs, by coyotes, bobcats, alligators and cougars. Baby raccoons are also killed by large owls, hawks, and eagles). If you are a flying insect, small bird, or fish, you’ll agree that frogs are predators. But frogs are also prey: herons and egrets eat adults, and leeches, dragonflies, newts, ane more eat tadpoles. So animals don’t sort neatly into the categories of predator and prey.

16 Search for wild horses fight, and look at the Images.

17 Berger, Joel. “Organizational systems and dominance in feral horses in the Grand Canyon.” Behavioral Ecology and Sociobiology 2, no. 2 (1977): 131-146.

18 Berger, Joel. “Organizational systems and dominance in feral horses in the Grand Canyon.” Behavioral Ecology and Sociobiology 2, no. 2 (1977): 131-146.

19 Greenfield, Joanna. “Hyena”. The New Yorker. November 11, 1996.

20 For an example of how freezing can save a life, see WildVisuals “Gazelle’s lucky escape from cheetah and hyena by playing dead.” In another remarkable video, an impala seems to have stopped breathing in the grasp of a leopard who tries to suffocate her, but after the leopard and hyena leave, resumes breathing, gathers her wits, and bounds away: 100100 Channel. “Baboons save impala from leopard and hyena.”

21 “Tonic immobility” Wikipedia.

22 Bazovkina, Daria V., Marina A. Tibeikina, Alexander V. Kulikov, and Nina K. Popova. “Effects of lipopolysaccharide and interleukin-6 on cataleptic immobility and locomotor activity in mice.” Neuroscience letters 487, no. 3 (2011): 302-304.

23 Griebel, Guy, Jeanne Stemmelin, and Bernard Scatton. “Effects of the cannabinoid CB1 receptor antagonist rimonabant in models of emotional reactivity in rodents.” Biological psychiatry 57, no. 3 (2005): 261-267.

24 Zamudio, Sergio R., Lucía Quevedo-Corona, Linda Garcés, and Fidel De La Cruz. “The effects of acute stress and acute corticosterone administration on the immobility response in rats.” Brain research bulletin 80, no. 6 (2009): 331-336.

25 Verwer, Cynthia M., Geert van Amerongen, Ruud van den Bos, and Coenraad FM Hendriksen. “Handling effects on body weight and behaviour of group-housed male rabbits in a laboratory setting.” Applied Animal Behaviour Science 117, no. 1 (2009): 93-102.

26 Hessing, Manfred JC, A. Mette Hagelsø, Willem GP Schouten, Piet R. Wiepkema, and Jan AM Van Beek. “Individual behavioral and physiological strategies in pigs.” Physiology & Behavior 55, no. 1 (1994): 39-46.


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