The organization of play fighting in the grasshopper mouse (Onychomys leucogaster): Mixing predatory and sociosexual targets and tactics

The body targets contacted, the type of contact made, and the patterns of d efense and counterattack elicited by those attacks are examined in the play fighting of captive male and female pairs of grasshopper mice. The nape wa s the most frequently contacted body target, irrespective of the type of co ntact made, be it nosing, allogrooming, biting, or striking with a forepaw. The types of defense varied with both body area contacted and type of atta ck performed. Based on the topography and pattern of contact, it was conclu ded that grasshopper mice, as is the case for many other muroid rodents, pr imarily attack and defend targets otherwise contacted during precopulatory encounters. However, grasshopper mice, which are obligate carnivores, also attack and defend predatory targets, although less frequently than sociosex ual targets. Surprisingly, predatory attacks were more likely to be counter attacked with predatory attacks, whereas sociosexual attacks were more like ly to be counterattacked with sociosexual attacks. Conspecific aggression i nvolves bites directed at the face, lower flanks, and dorsum. Neither the b iting of these areas nor the tactics of attack and defense usually associat ed with such bites were observed during the juvenile interactions. There we re no sex differences in either frequency or patterns of attack and defense in play fighting. The data presented for grasshopper mice shed light on th e issue of mixing behavior patterns from multiple functional systems during play. (C) 2000 Wiley-Liss, Inc.