RITUALIZED BEHAVIOR DURING COMPETITION FOR FOOD BETWEEN 2 FORMICINAE

Polyrhachis laboriosa and Camponotus brutus are two syntopic ants of t he African equatorial forest. Although they occupy two different ecolo gical niches (nesting area, diet, rhythms of activity), they are in co mpetition for the exploitation of large permanent food sources. C. bru tus, which is nocturnal, changed its rhythm of activity in the presenc e of large permanent food sources to exploit it day and night, while P . laboriosa, diurnal, did not change its rhythm of activity. Encounter s between workers of the two species at the food source always resulte d in duels, even though several other workers were present. When attac ked by C. brutus, P. laboriosa workers showed a novel ''flee-return'' strategy (fleeing over a 20-cm distance and returning to the source) i nstead of escaping definitively from the source and displayed ritualiz ed behavior (i.e., fleeing, raising the gaster, flexing the gaster). T hese types of behavior appeased C. brutus workers and enabled P. labor iosa to avoid overt aggression and to exploit the source in spite of t he presence of a competitor. C. brutus also exhibited ritualized behav ior during the duels (i.e., back-and-forthjerking of the body, series of light bites on a leg). C. brutus intimidated P. laboriosa rather th an really attacking it. This ritualization, used at an interspecific l evel, may be the result of a coevolutionary process or the effect of l earning that certain types of behavior are beneficial. In any case, bo th species benefit from the possibility of exploiting large permanent food sources through confrontations that never lead to overt aggressio n.