The trouble of categorizing play lies partly in the lack of apparent immediate biological function (Fagen,1981) or payback (Heinrich). It is typically costly in terms of energy expenditure, and potentially risky; noise or movement may attract unwanted attention, or a participant may be injured. However researchers are likely to generally agree that play helps to foster motor development, cognitive skills, and protocols for social interactions.
Play behaviour can be broadly classified as social play (involving other individuals) or non-social play (involving objects or locomotor play). It is likely to be initiated by a nose-to-nose approach, nudging, nipping, tossing the head and pawing at the prospective play partner (McDonnell and Poulin, 2002).
Some forms of play may include running, frolicking, chasing, bucking, jumping, prancing, leaping, manipulation of an object, play fighting and play sexual behaviour (McDonnell and Poulin, 2002).