National Geographic : 1994 Dec
* Play for the sake of play: Among the most vivacious of animals, a dolphin leaps near the bow wave of a freighter in the Pacific. Known for their antics in captivity, dolphins in the wild sometimes seek out human companions, such as surfers and scuba divers, to play with. Dolphins' superb swimming and navigational skills almost always prevent them from collid ing with ships they surf with. But in other species play can be costly. Falls or falling rocks can injure or kill intrepid climbers like ibex. Play can expose the young to predators-yellow baboons, for example, attack juvenile vervet monkeys playing too far from adult supervision. Or, as a merely irritating price of play, uproarious offspring may scare off prey that adults have been patiently stalking.