Is Play Behavior Sexually Dimorphic in Monogamous Species?

Play behavior involves both risks and benefits. It demands energy and exposes the animal to risks such as injuries, falls and greater susceptibility to predators (Fagen 1981). Sharpe et al. (2002) demonstrated that meerkats with less food availability could not afford the cost of play because they were either conserving their energy or looking for food. Furthermore, not only is play risky for the individual, sometimes the individual’s supervising parents are at risk as well (Fagen 1981; Nunes et al. 1999). However risky it may be, animals may benefit by practicing and preparing for future situations through play. For example, the animal may hone its locomotor and motor skills when play-fighting or chasing (Spinka et al. 2001; Nunes et al. 2004; Burghardt 2005), increase its reproductive fitness by engaging in sexual play (Mitchell 1979), maintain friendships or test dominance relationships (Pellis & Pellis 1998). If we are to assume that play is adaptive, species have presumably compromised between costs and benefits in a way in which the benefits outweigh the costs (Burghardt 2005). Polygynous species commonly exhibit sex differences in play (Poirier & Smith 1974; Mitchell 1979; Meaney et al. 1985; Nunes et al. 1999, 2004; Power 2000). In general, males of polygynous or promiscuous species (such as rats) demonstrate more roughand-tumble play (Pellis et al. 1997). This relationship holds true across taxa; squirrel monkey (Saimiri sciureus) males play rougher, more often and for longer Correspondence Karen L. Bales, Dept. of Psychology, One Shields Ave., University of California, Davis, CA 95616, USA. E-mail: [email protected]