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PSY/BIO 226: Comparative Animal Behavior
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animals at play


What is it? We all know it when we see it, but try to define it--I dare you!

No one knows for sure what play is, or why critters do it.

Some common elements include frolicksome leaps (sololocomotor rotational play), running, quick turns, rolling about, climbing, exaggerated or unconventional movements, knocking, kicking, throwing, tossing objects, wrestling, inhibited biting


chimp infants at play

Social play--play with others
Solitary play--play by self

foal at play

dog at play
Object play--play with things
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*it seems to have no immediate purpose or function

Because of the ultimate belief that attributes only arise under selective pressure, it is easy to think that play must have some adaptive value or it would not have evolved. But making that link has been hard, and in fact, play is COSTLY and DANGEROUS. Calls attention to an individual, makes noise, can result in injuries.

*It cannot be experimented with.

Trying to prevent a developing animal from playing is nigh on impossible, because to do so you have to screw up so many other aspects of an animal's life. How do you know that the missing play is all that accounts for any differences you see later?


1. Play seems to be restricted among various taxonomic groups.

Few invertebrates have been reported to play (an exception might be octopus: Service, 1998), nor have many poikilotherms, such as reptiles, been reported to play (a few exceptions: American alligators (Lazell & Spitzer, 1977), komodo dragons (Burghardt, 20020, juvenile African chameleons (Burghardt, 1982), and some turtles (Burghardt, 1998)).

Bird and mammal species are the taxonomic groups most often reported to show play.

2. Play is seen more often in species that have altricial rather than precocial young

ex. parrots play more than ducklings, chimps play more than antelope

3. Play is a characteristic of organisms with relatively long life-spans

ex. elephants play more than horses, chimps play more than macaques

4. Play is seen more often in species that are predators than it is in species that are prey animals

ex. wolves play more than rabbits

5. Play is seen more often in highly social species than it is in solitary species

ex. Yellow-bellied marmots play more than do their solitary-living cousins the groundhogs

6. Play is seen more in critters with more forebrain development and with greater visual and manipulative abilities

ex. parrots and monkeys play more than do sparrows or burros

7. Species that maintain significant levels of playfulness into adulthood typically also retain other neonatal characteristics (Crick, 1998)

Ex. adult domestic dogs play a lot (although not as much as puppies do), and also show many other neotenous characteristics (such as a shortened muzzle)

8. Play lacks any apparent, external goals

9. Play is generally only engaged in, in the absence of any other goal-directed situations

Ex. a youngster who really wants to eat does not play with his or her food. Play bouts may be broken off at the appearance of danger, etc. Play lacks the seriousness of "something that needs to be done."

10. Play is seen more in youngsters than it is in adults, and peaks during periods of maximal cortical development (Chick, 1998)

ex. young chimps play more often than do older adult chimps (Lawick-Goodall, 1968). Adults may play, however, when all other needs have been met.

11. The movements of play are generally borrowed from other behaviors, but often reordered and engaged in "out of context"

Ex. mock fighting, mating, predatory behavior, flight, eating. Incomplete or disordered sequences are common.

12. Play is more likely to be seen in relaxed, familiar conditions; it tends to disappear under stress

In absence of mom, for ex., most lion clubs will not play

13. Play is costly and dangerous

ex. 5 of 14 ibex kids sustained injuries during play bouts that resulted in limping. Think about falls, etc. Juvenile vervets are most often caught by baboons when the young vervets are playing.

14. Play appears to involve feelings of pleasure.

This is a hard one, because it smacks of anthropomorphism, but animals do appear motivated to play (think about your dog, for ex.) The argument goes like this: If humans feel pleasure in play and we evolved, then it is possible that our relatives also feel this pleasure. Pleasure could be the proximate motivator for play

15. Play often contains elements of surprise

(think about peek-a-boo) and the seeking of the unexpected, or thrills. Ex. ambush and pouncing of kittens Ex. tag games among squirrels aleviation of boredom? an interesting subject! Ex. ungulates chasing birds

16. Play appears often to overlap with exploration

Ex. from "What does this do?" to "What can I do with it?"

17. Play is typically signalled in some way as "other than" what it might appear; that is, it typically involves the communication, "This is play" (Beckoff, 1974; Beckoff & Allen, 1998)

dog play bow

ex. "play face" (relaxed open mouth display) Ex. play bow in canids Ex. laughter, not screams Ex. bites inhibited, claws retracted, etc.


Several theories

1. Surplus Energy Theory

Herbert Spencer (the "survival of the fittest" guy) said that infants play because they need to get rid of excess energy. Most efforts to test this hypothesis have failed, though. Ex. Muller-Schwarze found no increases in play in deprived black-tailed deer. Similarly, Chepko found no diffs in play of control and deprived goat kids.

2. Pleasure Theory

They do it because it feels good This is hard to test! Hasn't been tested yet

3. Arousal/Stimulation theory

sic. theory of behavioral hyperactivity Ellis suggested a drive that undelies play, a drive to increase arousal. But again, not easy to test, and not tested yet.

4. Practice Theory

Play helps kids to practice movements, etc. that they will need later. Ex. kids playing house, infants play-fighting, play-pouncing, etc. BUT play deprived animals seem to do fine. So, what?

5. Exercise theory

The use of muscles and other systems in play stimulates and helps contribute to their development. No data, but seems good.

6. Social Functions Theory

Play is where you figure out who's who in the hierarchy. Except, solitary animals play; something you would not expect were this the sole function of play.

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Beckoff, M. (1974). Social play and play-soliciting by infant canids. American Zoologist, 14, 323-340.

Beckoff, M. & Allen, C. (1998). Intentional communication and social play: How and why animals negotiate and agree to play. In M. Beckoff and J.A. Byers (eds.), Animal Play: Evolutionary, Comparative, and Ecological Perspectives. Cambridge, UK: Cambridge Univ. Press.

Burghardt, G.M. (1982). Comparison matters: Curiosity, bears, surplus energy, and why reptiles do not play. Behavioural and Brain Sciences, 5, 159-160.

Burghardt, G.M. (1998). The evolutionary origins of play revisited: Lessons from turtles. In M. Beckoff & J.A. Byers, (eds.), Animal Play: Evolutionary, Comparative, and Ecological Perspectives. Cambridge, UK: Cambridge Univ. Press.

Crick, G. (1998). What is play for? Sexual selection and the evolution of play. Keynote address presented at the annual meeting of The Association for the Study of Play, St. Petersburg, FL, February.

Lawick-Goodall, J. van (1968). The behaviour of free-living chimpanzees in the Gombe Stream Reserve. Animal Behaviour Monographs, 161-311.

Lazell, J.D., Jr. & Spitzer, N.C. (1977). Apparent play in an American alligator. Copeia, 1977, 188.

Service, R.F. (ed), Random samples: Suckers for fun. Science, 281, 909.

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