Last revised April 15, 2017.
G and me in an arena at the farm where I met him. He got the hang of pushing the ball around the ring, and needed little encouragement.1 Notice the slack rein and lack of bit, saddle, stirrups, and spurs.
What is play? Wikipedia tells us that “play is a range of voluntary, intrinsically motivated activities normally associated with recreational pleasure and enjoyment.2” Burghardt3 notes more characteristics of play: “ no obvious immediate function; pleasurable affect; sequentially variable; stimulation-seeking; quick and energetically expensive behaviour; exaggerated, incomplete, or awkward movement; most prevalent in juveniles; special “play” signals; a breakdown in role relationships; mixing of behavior patterns from several contexts; relative absence of threat or submission; and the relative absence of final consummatory acts (e.g., biting, intentional injury, killing, eating, or copulation)” One researcher sees play as an outgrowth of joy. Sounds right to me.
Play often contains incomplete sequences, reordered sequences, and incomplete movements.4 Through such movements, a young animal can work out the elements of a sequence and improve skills needed for each element.
Play falls into three categories: locomotor play, object play, and social play.5
In horses and other prey species, locomotor play focuses on aspects of anti-predator behavior, such as running and jumping. Object play focuses on activities related to food handling, such as manipulating balls and sticks with the mouth. Social play focuses on activities related to fighting and sexual behavior.6
In predators, locomotor play focuses on aspects of predator behavior, such as stalking, running and pouncing. Object play focuses on activities related to food handling, such as tearing up the sofa or chewing on a stick. Social play focuses on activities related to fighting and sexual behavior.
It is easy for us to spot play in children and domestic mammals. We’ve heard that there is a place where the deer and the antelope play. Those who have looked closely have found play in birds7 and even reptiles.8 But play is harder to spot in amphibians or insects9 or plants. Horses certainly play, and young horses are especially prone to play.10
Benefits of Play
Over 30 hypotheses have been advanced by scientists to account for play,11 but there is not solid support for any one of these hypotheses. Play likely has multiple benefits.
Many have reported that play is more common in young, healthy, well-fed and securely attached animals,12 suggesting its occurrence indicates well-being. But it is also more likely in barren or boring environments, suggesting that it serves to reduce boredom13 — a condition not associated with well-being.
Play is believed to improve chances of survival. In a youngster, play allows the development of social skills, including skill in social coordination and communication, social relationships, skill in combat, and development of strength and fitness.
In the following list of benefits, I do not think any of these is a direct cause of play. They are just benefits. But evolution might have made play rewarding because it could produce all of these benefits. When your horse pushes a ball or picks up your glove, it is not because he seeks social development or conditioning but because it is fun.
- Social development. Play may influence social development by developing social cohesion or skills.14 Through play, a young horse learns, develops friendships, and practices motor skills involved in social interactions.15 Young colts and fillies, for instance, may mount each other or their parents during play.16
- Conditioning. Movement in foals is important for conditioning the musculoskeletal system,17 and play accounts for most foal locomotion.18 Before the age of 6 weeks, play accounts for over 2/3 of total running, and 95% of high speed turns.19 Exercise during the first few months of a foal’s life20 and during adolescence21 has significant positive effects on the development of tendon strength and flexibility,22the musculoskeletal system,23 and gait. The physical proficiency of youngsters endures into adulthood24, so early play has long-term benefits for a horse’s musculoskeletal system and gait. A study of feral horses has found that play improved body condition in yearlings and increased the chance of survival. Play is exercise.
- Development of behavioral flexibility. Play is flexible in form, and may contribute to flexibility in behavior later in life.25 A horse needs complex, generalized skills for interacting with many social and physical environments.
- Practice for combat. Males frequently show greater motivation to play or initiate play in both domestic horses26 and other species27. At least some of this difference may be because play serves to develop skills in combat, which males will do more of as they age.
- Stimulation. A bored animal may be motivated to play. When they do so, they are stimulated, and rewarded for playing.
- Dissipate excess energy. When I was a kid, my mom often said to us boys “Why don’t you go out and play?”. She knew an essential truth: baseball is more safely played outdoors. And likely another: if you are feeling energetic, activity will consume some of that excess, returning you to the world of the exhausted.
- Stress reduction. Given toys such as a basketball, hose, and stick, a turtle that had been mutilating himself at the National Zoo spent about 30% of his active time playing with the toys, and self-mutilation decreased greatly.28 This turtle’s stress seems to have been reduced by the play. For us boys, perhaps my mom had discovered a useful principle: Rambunctiousness was triggered by stress and confinement, and outdoor play reduced that stress.
- It turns out that horses that play most in the paddock may be more prone to chronic stress.29 I imagine that a correlation between play and stress must be this: stress is undesired, horses know that play reduces stress, so the stressed horse chooses to play. With a correlation, of course, we could also conclude that play is stressful, and increases stress. The best test of these two theories would be to manipulate a horse’s stress level, and see how much play then occurs. Or to measure stress levels before and after play.
Two horses play with an empty feedbucket in the snow.30
I don’t think science yet has an accounting of the neural causes of play. So I’ll need to call upon my special training in making stuff up…
Chaser is a dog that has learned over 1,000 words. John Pilley, the psychology professor/owner/partner of Chaser, taught her these words.31 If he had used little treats as rewards, I suspect that Chaser would weigh as much as I do. Instead, Pilley used play as a reward. When Chaser got something right, he would reward her with play. It is hard to imagine anyone working for something that they did not want, did not enjoy. Play must cause pleasure.32 Perhaps it is also triggered by pleasure.
I believe that animals play because it is fun for them to do so.33 When it happens, there is likely a big release of dopamine. As I say in the section on the Neuropsychology of the Horse, “The brain contains several dopamine pathways which are involved when we are motivated by a reward, when we meet a goal, or when drugs or alcohol make us feel intoxicated. Dopamine underlies both addiction and the effectiveness of positive reinforcement. Operating in the reward circuit, dopamine is released to produce pleasure.”
I suspect that there are elevated levels of endorphins present at the initiation of play. You’ll recall that endorphins are responsible for the euphoria of a runner’s high. They may also be stimulated by laughter, and I suspect by play. Play may trigger the release of endorphins in the same way that running triggers the release of endorphins. After running, the endorphins begin to dissipate, and the only solution is to run some more. Back in my running days, I sometimes had to pull over on my home from an event to run a little bit more. Foals may have play bouts for the same reason.
If play triggers the release of dopamine and endorphins, and if play has all the benefits that are described above, then it would stand to reason that birds and mammals evolved to release these neurochemicals in young animals to motivate play.
Play seems to be rewarding.
Not every horse in the pasture is equally likely to be found playing.34
- Play is more likely when diet and nutrition are adequate35, particularly for young colts.36
- While colts and fillies spend equal amounts of time playing, colts are more likely to initiate play37, and spend more time than fillies in play fighting.
- Colts engage in interactive play more often than fillies. In one study,38 when foals were 1-4 weeks old, 48% of a colt’s play activities were interactive play, whereas only 12% of a filly’s play activities were interactive play. When they did engage in interactive play, a typical play session lasted twice as long for a colt as for a filly on average. These differences between the sexes become even greater as the foals moved from weeks five to eight.
- Play is more common in geldings than stallions.39
- Play is more common in younger animals40. Playfulness is a quality that differentiates older horses from younger ones.
Changes in Rate of Play
Play drops off with age — usually. Play is most common in the young of all animals that play. In precocial animals (those hatched or born able to move about at birth) such as the horse, play begins at birth. In altricial animals (those hatched or born in a state that requires parental care and feeding) like the human, play begins later and may last longer. Elsewhere I discuss neoteny (the retention of juvenile features through sexual maturity) which is believed to affect humans and dogs, and which extends the play period indefinitely.
Play drops off as the temperature rises.
Mean rate of play at various temperatures. Play drops off as temperatures rise from 5 deg C (41 deg F).41
Horse play begins at mother’s side, and young foals play alone or with their moms. Moms play back, or at least tolerate rough treatment. By the age of 8 weeks, foals increasingly play with others of their age and older, if available.42
Play provides mental stimulation
If there are no foals handy, foals will try playing with anyone. I once was standing in a pasture surrounded by carrot lovers. A foal, unweaned, wanted to get in on whatever was going on, but was too young to appreciate a good carrot. The bigger horses kept crowding him out. Finally he found an opening, and walked up to within a few feet of me. Splat! He was carrying a mouth full of water, and squirted it out on me. I was too amazed for words, and watched as he returned to the water tub for another mouthful. This was a game that he had invented, and a wonderful one. Try teaching your horse to do that with a clicker! What else is involved in foal play? Let YouTube.com show you. Foal play is uninterrupted invention.
Whatever the explanation for play, the brain must have something to do with it. Playful behavior is behavior that produces mental stimulation and feels good. Bigger brains might enjoy it more. Three Canadian researchers43 looked at the relationship between brain size in various Orders of mammals (an Order is a classification between Kingdom, Phylum, Class, and Family, Genus, Species) and the prevalence and complexity of play. Their conclusion was that at the level of Order, the average size of brains correlated with the prevalence and complexity of play. But the relationship is not so simple. Domesticated breeds appear to be more playful than their wild ancestors,44 but often have brains that are 30% smaller45, and within an Order there are wide variations in playfulness across species.
Initiating Play, Halting Play
And in the case of the horse, how does horse play differ from fighting? If horse A chooses to play with horse B, how does he tell horse B that this is play? If the play gets too rough, how does a horse deescalate the play?
We know our dogs, and know that a “play bow” is a signal from a dog to another dog that “I want to play”. In the play bow, the front legs go out, front end goes down, back end stays up, and the tail is up, making broad waves. The play bow may include dilated pupils and an open mouth. After holding this position for a bit, the dog may break into a run in some random direction. The signal is so clear that even humans know it.
Typical play soliciting gesture of a young dog (1 year old male)46
Dogs also have a position that they take if the play gets too rough. The dog may tuck his tail over his genitals, roll onto his back exposing stomach and throat, pull ears flat and back. He may turn its head to avoid eye contact, and partly close his eyes. A few drops of urine may be sprinkled. The overall position lowers this submitting dog’s threat (avoiding eye contact and partly closing eyes, exposing stomach and throat) and protects some vulnerable parts (tail tuck and ears back).
So how do horses signal that they want to play, and how do they signal if play has gotten too rough? I have not seen any signals for “let’s play”. It seems foals simply initiate running or jumping, and other nearby foals join in. If play becomes too rough, there are clear signals that break it off: ears back, and optional kicking.47
My horse G with a short lead rope. He plays by grabbing the free end in his mouth, leading himself, and sometimes by twirling it.48
1 Image source: David Stang.
2 “Play (activity)” WIkipedia. https://en.wikipedia.org/wiki/Play_(activity)
3 Burghardt, Gordon M. “On the origins of play.” Play in animals and humans (1984): 5-41.
4 Ficken, Millicent S. “Avian play.” The Auk (1977): 573-582.
5 Burghardt, G.M. “The evolutionary origins of play revisited: Lesson from turtles” In M. Bekoff & J.A. Byers (Eds.), Animal play: Evolutionaty, comparative, and ecological perspectives 1998. Pp 1-26. Cambridge, England: Cambridge University Press.; Burghardt, G.M. “Play”. In G. Greeway and M. Harraway (Eds.), Comparative Psychology: A handbook. 1998. New York, Garland. Pp. 757-767.
6 Power, Thomas G. Play and exploration in children and animals. Psychology Press, 1999.
7 Ficken, Millicent S. “Avian play.” The Auk (1977): 573-582.
8 Burghardt, G. M. “Play in reptiles.” New encyclopedia of reptiles and amphibians (2002): 112-113.
9 Charles Darwin cites a friend’s story of ants chasing and pretending to bite each other, like so many puppies. Darwin, Charles. “The descent of man, 2 Vols.” London 81 (1871): 130-1. page 448.
10 Fagen, R. M. & George, T. K. 1977. Play behavior and exercise in young ponies (Equus caballus L.). Behavioral Ecology and Sociobiology, 2, 267-269.; Crowell-Davis, S. L., Hosupt, K. A. & Kane, L. 1987. Play development in Welsh pony (Equus caballus) foals. Applied Animal Behaviour Science, 18, 119-131.; Zharkikh, T. L. 1999. Development of the Przheval’skii horse, Equus przewalskii (Perissodactyla) play behavior at the ‘Askania-Nova’ Reserve. Zoologichesky Zhurnal, 78, 878-884.; McDonnell, S. M. & Poulin, A. 2002. Equid play ethogram. Applied Animal Behaviour Science, 78, 263-290.
11 Smith, P. K. 1982. Does play matter? Functional and evolutionary aspects of animal and human play. Behavioral Brain Science, 5, 139e184.; Baldwin, J. D. 1986. Behavior in infancy: exploration and play. In: Comparative Primate Biology. Vol. 2A. Behavior, Conservation and Ecology (Ed. by G. Mitchell & J. Erwin), pp. 295-326. New York: A. R. Liss
12 Donaldson, Tammy M., Ruth C. Newberry, Marek Špinka, and Sylvie Cloutier. “Effects of early play experience on play behaviour of piglets after weaning.” Applied Animal Behaviour Science 79, no. 3 (2002): 221-231.; Fraser AF, Broom DM (1990) Farm animal behaviour and welfare.
CAB International, London.; Hausberger, Martine, Séverine Henry, Claire Larose, and Marie-Annick Richard-Yris. “First suckling: A crucial event for mother-young attachment? An experimental study in horses (Equus caballus).” Journal of Comparative Psychology 121, no. 1 (2007): 109.; Henry, Séverine, Marie-Annick Richard-Yris, Sylvie Tordjman, and Martine Hausberger. “Neonatal handling affects durably bonding and social development.” PloS one 4, no. 4 (2009): e5216.
13 Burghardt, Gordon M. The genesis of animal play: Testing the limits. Mit Press, 2005.
14 Caro, T. M. 1988. Adaptive significance of play: are we getting any closer? Trends in Ecology & Evolution, 3, 50-54.; Holmes, W. G. 1995. The ontogeny of littermate preferences in juvenile golden-mantled ground squirrels: effects of rearing and relatedness. Animal Behaviour, 50, 309-322
15 Fagen, R. M. 1981. Animal Play Behavior. New York: Oxford University Press; Smith, P. K. 1982. Does play matter? Functional and evolutionary aspects of animal and human play. Behavioral Brain Science, 5, 139-184; Caro, T. M. 1988. Adaptive significance of play: are we getting any closer? Trends in Ecology & Evolution, 3, 50-54.
16 Crowell-Davis, Sharon L., Katherine A. Houpt, and L. Kane. “Play development in Welsh pony (Equus caballus) foals.” Applied Animal Behaviour Science 18, no. 2 (1987): 119-131.
17 Kurvers, C. M. H. C., van Weeren, P. R., Rogers, C. W. & van Dierendonck, M. C. 2006. Quantification of spontaneous locomotion activity in foals kept in pastures under various management conditions. American Journal of Veterinary Research, 67, 1212e1217.
18 Fagen, R. M. & George, T. K. 1977. Play behavior and exercise in young ponies (Equus caballus L.). Behavioral Ecology and Sociobiology, 2, 267e269.
19 Fagen, Robert M., and Timothy K. George. “Play behavior and exercise in young ponies (Equus caballus L.).” Behavioral Ecology and Sociobiology 2, no. 3 (1977): 267-269.
20 Cherdchutham, W., Meershoek, L. S., van Weeren, P. R. & Barneveld, A. 2001. Effects of exercise on biomechanical properties of the superficial digital flexor tendon in foals. American Journal of Veterinary Research, 62, 1859e1864.
21 Firth, E. C., Rogers, C. W., Doube, M. & Jopson, N. B. 2005. Musculoskeletal responses of 2-year-old thoroughbred horses to early training. 6. Bone parameters in the third metacarpal and third metatarsal bones. New Zealand Veterinary Journal, 53, 101-112.; Rogers, C. W., Firth, E. C. & Anderson, B. 2005. Musculoskeletal responses of 2-year-old thoroughbred horses to early training. 5. Kinematic effects. New Zealand Veterinary Journal, 53, 95-100.
22 Cherdchutham, W., Meershoek, L. S., van Weeren, P. R. & Barneveld, A. 2001. Effects of exercise on biomechanical properties of the superficial digital flexor tendon in foals. American Journal of Veterinary Research, 62, 1859e1864.
23 Brama, P. A. J., TeKoppele, J. M., Bank, R. A., Barneveld, A. & van Weeren, P. R. 2002. Biochemical development of subchondral bone from birth until age eleven months and the influence of physical activity. Equine Veterinary Journal, 34, 143e149.
24 Back, W., Schamhardt, H. C., Hartman, W., Bruin, G. & Barneveld, A. 1995. Predictive value of foal kinematics for the locomotor performance of adult horses. Research in Veterinary Science, 59, 64-69.; Santamaría, Susana, Maarten F. Bobbert, Willem Back, Ab Barneveld, and P. René van Weeren. “Evaluation of consistency of jumping technique in horses between the ages of 6 months and 4 years.” American journal of veterinary research 65, no. 7 (2004): 945-950.
25 Fagen, Robert. “Evolutionary issues in development of behavioral flexibility.” In Ontogeny, pp. 365-383. Springer US, 1982.
26 Crowell-Davis, S. L., Hosupt, K. A. & Kane, L. 1987. Play development in Welsh pony (Equus caballus) foals. Applied Animal Behaviour Science, 18, 119-131
27 Pellis, S. M., Field, E. F., Smith, L. K. & Pellis, V. C. 1997. Multiple differences in the play fighting of male and female rats. Implications for the causes and functions of play. Neuroscience and Biobehavioral Reviews, 21, 105-120; Pasztor, T. J., Smith, L. K., MacDonald, N. K., Michener, G. R. & Pellis, S. M. 2001. Sexual and aggressive play fighting of sibling Richardson’s ground squirrels. Aggressive Behavior, 27, 323-337.; Nunes, S., Muecke, E., Sanchez, Z., Hoffmeier, R. R. & Lancaster, L. T. 2004. Play behavior and motor development in juvenile Belding’s ground squirrels (Spermophilus beldingi). Behavioral Ecology and Sociobiology, 56, 97-105.
28 Burghardt, Gordon M., Brian Ward, and Roger Rosscoe. “Problem of reptile play: Environmental enrichment and play behavior in a captive Nile soft‐shelled turtle, Trionyx triunguis.” Zoo Biology 15, no. 3 (1996): 223-238.
29 Céline Rochais, Carole Fureix, Martine Hausberger. On the significance of puzzling behaviours: What do yawning and adult play tell us about horse (Equus caballus) welfare. 2nd Congress of International Equine Science Meeting (IESM 2012), Mar 2012, Regensburg, Germany. Xenophon Verlag, pp.978-39808134-33, Proceedings of the 2nd IESM; Hausberger, Martine, Carole Fureix, Marie Bourjade, Sabine Wessel-Robert, and Marie-Annick Richard-Yris. “On the significance of adult play: what does social play tell us about adult horse welfare?.” Naturwissenschaften 99, no. 4 (2012): 291-302.
30 Image source: David Stang. My horse G is on the right, a friend on the left.
31 Pilley, J. W., & Hinzmann, H. (2013). Chaser: Unlocking the genius of the dog who knows a thousand words. Houghton Mifflin Harcourt.
32 In humans, there are a number of studies suggesting that play can reduce depression. For example: Li, Jinhui, Yin-Leng Theng, and Schubert Foo. “Effect of exergames on depression: A systematic review and meta-analysis.” Cyberpsychology, Behavior, and Social Networking 19, no. 1 (2016): 34-42.
33 Bekoff, Marc, and Colin Allen. “Intentional communication and social play: how and why animals negotiate and agree to play.” Animal play: Evolutionary, comparative, and ecological perspectives (1998): 97-114. P. 97
34 Cameron, Elissa Z., Wayne L. Linklater, Kevin J. Stafford, and Edward O. Minot. “Maternal investment results in better foal condition through increased play behaviour in horses.” Animal Behaviour 76, no. 5 (2008): 1511-1518.
35 Southwick 1967; Loy 1970; Baldwin & Baldwin 1974; Lee 1984; Barrett et al. 1992; Sommer & Mendoza-Granados 1995; ungulates: Geist 1971; Mu¨ller-Schwarze et al. 1982; rodents: Smith 1991); (e.g. Baldwin & Baldwin 1976; Nunes et al. 1999; Sharpe et al. 2002; (e.g. meerkats, Suricata suricatta: Sharpe et al. 2002; gelada baboons, Theropithecus gelada: Barrett et al. 1992; Hanuman langurs, Presbytis entellus: Sommer & Mendoza-Granados 1995; Belding’s ground squirrels, Spermophilus beldingi: Nunes et al. 1999; white-tailed
36 Cameron, Elissa Z., Wayne L. Linklater, Kevin J. Stafford, and Edward O. Minot. “Maternal investment results in better foal condition through increased play behaviour in horses.” Animal Behaviour 76, no. 5 (2008): 1511-1518.
37 Cameron, Elissa Z., Wayne L. Linklater, Kevin J. Stafford, and Edward O. Minot. “Maternal investment results in better foal condition through increased play behaviour in horses.” Animal Behaviour 76, no. 5 (2008): 1511-1518.
38 Crowell-Davis, S. L., Hosupt, K. A. & Kane, L. 1987. Play development in Welsh pony (Equus caballus) foals. Applied Animal Behaviour Science, 18, 119-131
39 Mcdonnell, S.M., Poulin, A., 2002. Equid play ethogram. Appl. Anim. Behav. Sci. 78 (2–4), 263–290.; Tyler, S.J., 1972. The behaviour and social organisation of the New Forest Ponies. Anim. Behav. Monogr. 5, 85–196.; Waring, G.H., 2003. Horse Behavior, second edition. William Andrew Publishing, Norwich, NY.
40 Mcdonnell, S.M., Poulin, A., 2002. Equid play ethogram. Appl. Anim. Behav. Sci. 78 (2–4), 263–290.; Tyler, S.J., 1972. The behaviour and social organisation of the New Forest Ponies. Anim. Behav. Monogr. 5, 85–196.; Waring, G.H., 2003. Horse Behavior, second edition. William Andrew Publishing, Norwich, NY.
41 Crowell-Davis, S. L., Hosupt, K. A. & Kane, L. 1987. Play development in Welsh pony (Equus caballus) foals. Applied Animal Behaviour Science, 18, 119-131
42 Crowell-Davis, Sharon L., Katherine A. Houpt, and L. Kane. “Play development in Welsh pony (Equus caballus) foals.” Applied Animal Behaviour Science 18, no. 2 (1987): 119-131.; Tyler, S.J., 1972. The behaviour and social organization of the New Forest ponies. Anim. Behav. Monogr., 5: 85-196.
43 Iwaniuk, Andrew N., John E. Nelson, and Sergio M. Pellis. “Do big-brained animals play more? Comparative analyses of play and relative brain size in mammals.” Journal of Comparative Psychology 115, no. 1 (2001): 29-41.
44 Budiansky, Stephen. The covenant of the wild: why animals chose domestication: with a new preface. Yale University Press, 1992.
45 These comparison in brain size obviously adjust for the size of the animal. There are sophisticated allometric formulas. See Kruska, Dieter. “Mammalian domestication and its effect on brain structure and behavior.” In Intelligence and evolutionary biology, pp. 211-250. Springer Berlin Heidelberg, 1988.
46 Image source: Wikipedia. https://commons.wikimedia.org/wiki/File:Vorderkoerpertiefstellung_THWZ.jpg
47 Crowell-Davis, S. L., Hosupt, K. A. & Kane, L. 1987. Play development in Welsh pony (Equus caballus) foals. Applied Animal Behaviour Science, 18, 119-131
48 Image source: David Stang.