Do animals play and is there a benefit from play? Do animals play, and if so, how? Is there a benefit to play behavior? How

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1 Kieffer 1 Do animals play and is there a benefit from play? Do animals play, and if so, how? Is there a benefit to play behavior? How could play behavior have evolved? Several investigators have looked into these topics and come up with some similar, and some very different, answers. Both mammals and birds species are known to play (Barrett et al. 1992, Pellis 1991, Miller and Byers 1991, Cheney 1978) and according to the various definitions of play, some species play and some do not. Ortega and Bekoff (1987) defined play broadly as any purposeless motor activity that includes patterns from other contexts such as mating or stalking. Harcourt (1991a) described play as activity having no immediate benefits for the animal, and it may actually incur a high cost due to an increased risk of predation during play. How do animals play? Several different types of play have been defined, most commonly in mammals. In a study of baboons (Papio cynocephalus ursinus), Cheney (1978) described play as locomotor patterns that involved chasing or wrestling among immature animals. Caro (1995) observed cheetahs (Acinonyx jubatus) and characterized five types of play: locomotor, contact social, object, non-contact social, and exploration. Locomotor play included rushing around vigorously and bounding about with no immediate benefit. Contact social play was patting, biting, kicking, or grasping family members. Object play included patting, biting, kicking, stalking or carrying various objects. Non-contact play included stalking, crouching, chasing, fleeing, or rearing up towards family members but without

2 Kieffer 2 actual contact with them and exploration play was considered sniffing at objects with no apparent benefit. Gomedio (1988) found four distinct types of play in Cuvier s gazelle (Gazella cuvieri). Two were similar to Caro (1995), locomotor play, excessive and apparently unbeneficial movement, such as running or fast turns and stops, and object play or play-fighting with inanimate objects. However, two new categories were added; sexual play and play-fighting. Sexual play consisted of one animal following another followed sometimes by foreleg-kicking and mounting. Play-fighting was between two or more individuals and butting, sparring, clashing, pushing and neck-fighting occurred. Although most of the research has involved mammals, some avian play has been observed. Captive immature American Kestrels (Falco sparvirius) play with objects in various manners and specifically, prefer to play with objects that resemble natural prey (Negro et al. 1995). In this study, play was determined to be any manipulation of the object placed in the kestrels pens. Kilham (1974) also observed play by various woodpeckers in two forms. He observed a Downy Woodpecker (Picoides pubescens) dodging in and out between a courting Whitebreasted Nuthatch (Sitta carolinensis) and his mate with similar observations in Hairy Woodpeckers (Picoides villosus). The second form of play observed was wild, erratic flight looping in, out and around trees by various woodpecker species. So why play?

3 Kieffer 3 The top theory is that play develops adult predator and fighting skills, social bonding and communication, cognitive and innovative abilities, and energy regulation (Bekoff and Byers 1992). Caro (1995) suggested that for cheetahs there was a benefit to play that may be achieved in adulthood such as chases, stalking practice and predator avoidance. Ficken (1977), examined avian play and suggested that play: 1) enhances muscular growth and development, 2) encourages discoveries and experimentation in the environment in relation to the animal s behavior, and 3) adjusts the animal to the relationships that occur in adulthood in social species. Play behavior, therefore, seems to be an important part of the development of young of many species, but not all animals play. Who does not play? In a study comparing altricial and precocial species of birds, precocial young demonstrated a lack of play (Ortega and Bekoff 1987). Because precocial young are more self-sufficient from hatching, an individual s time was spent mostly on foraging, with play being limited to small amounts of locomotor play. Altricial young, however, being more dependent on parental care, had more time to interact with conspecifics and, in turn, play. Therefore, in altricial species, play behavior was selected for because it was not detrimental to the young. Precocial young that play, however, incur a higher cost because play burns energy as well as taking time away from foraging which could promote growth and fitness. Adults of most species studied did not play. Adult American Kestrels showed no interest in prey items left in the cage, and no play was observed (Negro et al. 1996). Adult South American fur seals (Arctocephalus australis) did

4 Kieffer 4 not show signs of play (Harcourt 1991b). As gazelles aged, play decreased. The closer the fawns were to reaching adulthood, the less play was observed (Gomendio 1988). Play is mainly associated with, but not restricted to, the juveniles within a species. Costs vs. benefits of play In relation to costs, not only does play increase the immediate energy load, but play may come with a high risk of increased predation. Harcourt (1991a) studied play in the South American fur seal and determined that 84.6% of observed attacks and kills on pups occurred while pups were playing. Play activity is thought to be highly conspicuous (Harcourt 1991a), which may encourage predation. Another risk incurred by play behavior is alerting prey that a predator is present. Caro (1987) found that cheetah cubs alerted prey 16.4% of the time that the mother was stalking. This number is partially attributed to play activities in the young. This risk, although indirect, may harm the young if play causes the adults to miss an opportunity for a kill, which, in turn, decreases food for the young. However, there are benefits to play as well. The benefits of this potentially energetically-depleting behavior are not immediate. The fitness of the individual may only be higher when the animal reaches maturity (Gomendio 1988). Animals go through experimentation and muscle building while playing as juveniles which have led them successfully to adulthood. Play likely allowed the animal to learn about the social hierarchy and the environment in which it will reside as an adult, but are all the benefits received later in life, or are there some immediate benefits to play?

5 Kieffer 5 Gomendio (1988) stated that because natural selection operates at all stages of a life cycle, behavior must benefit both the current stage as well as future stages leading to the idea of an ecological niche for play in immature animals. The ontogeny of play, therefore, must have an adaptive significance within a species, or it would have been selected against because it is energetically costly. Conclusion Play behavior has evolved to benefit both the young and adults. The young benefiting in each stage of life, including immaturity and the adults by the experiences gained through playing. However, that does not mean that play is mandatory and will occur in all species of animals. Natural selection has selected for this behavior in some species and not others. Play has developed in those species where the benefits outweigh the costs. The adaptive significance of play is that although this behavior has benefits for many species, little or no play is more beneficial to others and it has evolved accordingly.

6 Kieffer 6 Literature Cited Barrett, L., Dunbar, R.I M., and Dunbar, Patsy Environmental influences on play behaviour inimmature gelada baboons. Anim. Behav. 44: Bekoff, M. and Byers, J. A Time, energy and play. Anim. Behav. 44: Caro, T. M Indirect costs of play: Cheetah cubs reduce maternal hunting success. Anim. Behav. 35: Caro, T. M Short-term costs and correlates of play in cheetahs. Anim. Behav. 49: Cheney, D. L The play partners of immature baboons. Anim. Behav. 26: Ficken, M. S Avian Play. Auk 94: Gomendio, M The development of different types of play in gazelles: implications for the nature and function of play. Anim. Behav. 36: Harcourt, R The development of play in the South American fur seal. Ethology 88: Harcourt, R Survivorship costs of play in the South American fur seal. Anim. Behav. 42: Kilham, L Play in Hairy, Downy, and other woodpeckers. Wilson Bull. 86: Miller, M. N. and Byers, J. A Energetic cost of locomotor play in pronghorn fawns. Anim. Behav. 41: ,

7 Kieffer 7 Negro, J. J., Bustamante, J., Milward, J., and Bird, D. M Captive fledgling American kestrels prefer to play with objects resembling natural prey. Anim. Behav. 52: Ortega, J. C. and Bekoff, M Avian Play: Comparative Evolutionary and Developmental Trends. Auk 104: Pellis, S. M How motivationally distinct is play? A preliminary case study. Anim. Behav. 42: Study Questions 1. In what way do animals benefit from play? 2. Why do precocial young not play while altricial young are known to play? 3. What is the top theory as to why play occurs in animals?