Figure 1.
Stereotyped fighting and the winner effect in crickets.
A Pictograms illustrating the escalating levels of aggression that characterize cricket fights (adopted from [15]): Level 0 mutual avoidance: non-aggressive interaction. Level 1 pre-established dominance: one cricket attacks, the other retreats. This level is in accordance with the avoiding behaviour of losers. Level 2 antennal fencing: the two crickets fence with their antennae. Level 3 mandible spreading (unilateral): one cricket displays broadly spread mandibles. Level 4 mandible spreading (bilateral): both crickets display their spread mandibles. Level 5 mandible engagement: the mandibles of both contestants interlock. Level 6 grappling: all-out fighting involving repetitive biting, mandible pushing, and opponent flipping. B, C Bar graphs giving the level and respectively duration of aggression for encounters between pairs of male, weight matched, fight-inexperienced crickets (naive, N), winners of one previous encounter (W1), winners of two previous encounters (W2) for inter-fight intervals (IFI) of 5 min (left side, grey bars) and 20 min (right side, dark bars). Numbers in parenthesis in (B) give the number of contests for each round, circles with bar the median, boxes the interquartile range and asterisks significant differences between all rounds in the tournament (Kruskal-Wallis one way variance test, *** p<0.001, n.s. not significant).
Figure 2.
Effect of amine-receptor antagonists on the winner effect.
A, B Bar graphs giving the level, and respectively duration of aggression for encounters between pairs of male, weight matched, fight-inexperienced crickets (naive, N), winners of one previous encounter (W1), winners of two previous encounters (W2) for inter-fight intervals (IFI) of 5 min following treatment with (from left to right): vehicle (white bars), propranolol (cross-hatched bars bar), yohimbine (stippled bars), fluphenazine (bold-hatched bars) or epinastine (dark grey bars). Numbers in parenthesis in (A) give the number of contests for each round, circles with bar the median, boxes the interquartile range and asterisks significant differences between all rounds for each tournament (Kruskal-Wallis one way variance test, ** p<0.01, *** p<0.001, n.s. not significant).
Table 1.
Numerical summary of the aggressiveness exhibited by crickets treated with amine-receptor blockers in knockout tournaments.
Figure 3.
Influence of different winning experiences on subsequent aggression.
A, B Pictograms illustrating the paradigms “winning without fighting” and respectively “fighting without winning”. C, D Bar graphs giving the level and respectively duration of aggression for encounters between pairs of male, weight matched crickets with different winning experiences, from left to right: control - no previous fighting experience (naive, N, white bars), “winning without fighting”, i.e. crickets that were tested following 2 successive encounters against non-aggressive losers (W-F2, stippled bar), “fighting without winning”, i.e. crickets that were tested following 2 successive fights that were interrupted before a win occurred (F-W2, grey bar). The inter-fight interval (IFI) was 5 min in all cases. Numbers in parenthesis in (C) give the number of contests for each round, circles with bar the median, boxes the interquartile range and asterisks significant differences between all rounds in the tournament (U test, * p<0.05, ** p<0.01).