section_path: Other animals
section_name: Other animals
paragraph_text: Other animals
  
  Evolutionary psychologists believe that there must be an important benefit of play, as there are so many other reasons to avoid it; observations have shown it has arisen independently in such varied groups as mammals, birds, reptiles, amphibians, fish, and invertebrates. Animals are often injured during play, become distracted from predators, and expend valuable energy. In rare cases, play has even been observed between different species that are natural enemies such as a polar bear and a dog. Yet play seems to be a normal activity with animals who occupy the higher strata of their own hierarchy of needs. Animals on the lower strata, e.g. stressed and starving animals, generally do not play. However, in wild Assamese macaques physically active play is performed also during periods of low food availability and even if it is at the expense of growth, which highlights the developmental and evolutionary importance of play.
  
  The social cognitive complexity of numerous species, including dogs, have been explored in experimental studies. In one such study, conducted by Alexandra Horowitz of the University of California, the communication and attention-getting skills of dogs were investigated. In a natural setting, dyadic play behavior was observed; head-direction and posture was specifically noted. When one of the two dogs was facing away or otherwise preoccupied, attention-getting behaviors and signals (nudging, barking, growling, pawing, jumping, etc.) were used by the other dog to communicate the intent and/or desire to continue on with the dyadic play. Stronger or more frequent signaling was used if the attention of the other dog was not captured. These observations tell us that these dogs know how play behavior and signaling can be used to capture attention, communicate intent and desire, and manipulate one another. This characteristic and skill, called the "attention-getting skill" has generally only been seen in humans, but is now being researched and seen in many different species.
  
  Observing play behavior in various species can tell much about the player's environment (including the welfare of the animal), personal needs, social rank (if any), immediate relationships, and eligibility for mating. Play activity, often observed through action and signals, serves as a tool for communication and expression. Through mimicry, chasing, biting, and touching, animals act out in ways that send messages to one another; whether it's an alert, initiation of play, or expressing intent. When play behavior was observed for a study in Tonkean macaques, it was discovered that play signals weren't always used to initiate play; rather, these signals were viewed primarily as methods of communication (sharing information and attention-getting).
  
  One theory—"play as preparation"—was inspired by the observation that play often mimics adult themes of survival. Predators such as lions and bears play by chasing, pouncing, pawing, wrestling, and biting, as they learn to stalk and kill prey. Prey animals such as deer and zebras play by running and leaping as they acquire speed and agility. Hoofed mammals also practice kicking their hind legs to learn to ward off attacks. Indeed, time spent in physical play accelerates motor skill acquisition in wild Assamese macaques. While mimicking adult behavior, attacking actions such as kicking and biting are not completely fulfilled, so playmates do not generally injure each other. In social animals, playing might also help to establish dominance rankings among the young to avoid conflicts as adults.
  
  John Byers, a zoologist at the University of Idaho, discovered that the amount of time spent at play for many mammals (e.g. rats and cats) peaks around puberty, and then drops off. This corresponds to the development of the cerebellum, suggesting that play is not so much about practicing exact behaviors, as much as building general connections in the brain. Sergio Pellis and colleagues at the University of Lethbridge in Alberta, Canada, discovered that play may shape the brain in other ways, too. Young mammals have an overabundance of brain cells in their cerebrum (the outer areas of the brain—part of what distinguishes mammals). There is evidence that play helps the brain clean up this excess of cells, resulting in a more efficient cerebrum at maturity.
  
  Marc Bekoff (a University of Colorado evolutionary biologist) proposes a "flexibility" hypothesis that attempts to incorporate these neurological findings. It argues that play helps animals learn to switch and improvise all behaviors more effectively, to be prepared for the unexpected. There may, however, be other ways to acquire even these benefits of play (the concept of equifinality). The social benefits of play for many animals, for example, could instead be garnered by grooming. Patrick Bateson maintains that equifinality is exactly what play teaches. In accordance with the flexibility hypothesis, play may teach animals to avoid "false endpoints". In other words, they harness the childlike tendency to keep playing with something that works "well enough", eventually allowing them to come up with something that might work better, if only in some situations. This also allows mammals to build up various skills that could come in handy in entirely novel situations.
  
  A study on two species of monkeys Semnopithecus entellus and Macaca mulatta that came into association with each other during food provisioning by pilgrims at the Ambagarh Forest Reserve, near Jaipur, India, shows the interspecific interaction that developed between the juveniles of the two species when opportunity presented itself.