Assessment strategy of fighting crickets revealed by manipulating information exchange

The assessment strategy used by adult male crickets, Gryllus bimaculatus (de Geer), during conspecific aggression was deduced from the effects of handicaps (disabled mandibles, blackened eyes, size) and altered aggressive motivation (after defeat and flying) on aggressiveness, fight duration and win probability under laboratory conditions. The contestants received either the same (symmetrical) or different (asymmetrical) treatments. Despite handicaps, all crickets showed essentially normal escalating fighting behaviour. In symmetrical contests, fights became even harsher and longer with multiple handicaps. In asymmetrical contests, neither disabling the mandibles nor blackening the eyes significantly influenced win probability. However, ‘blinded’ crickets nearly always defeated opponents with disabled mandibles that could not inflict bites. Furthermore, small crickets and losers showed physical fighting more frequently when prevented from seeing. Handicap effects became more pronounced when both contestants were flown, to maximize aggressive motivation, before fighting. Our findings conform to the cumulative assessment hypothesis. We conclude, first, that contestants need longer to accumulate the cues required to surpass a threshold to flee when visual and physical inputs are reduced. Second, the decision to flee is based solely on the opponent's actions. Third, flying enhances aggressiveness by reducing disparities in motivation, making other disparities, such as in weaponry, more decisive. Thus, a cricket's aggressiveness is a trade-off between its inherent, experience-dependent agonistic motivation and the accumulated perceived actions of the adversary.