Male attractiveness covaries with fighting ability but not with prior fight outcome in house crickets

In many species males that tend to win fights against other males are more attractive to females. There are three ways in which male fighting ability and attractiveness may be associated; (1) attractiveness and fighting ability are influenced by the same underlying traits (e.g., body size), (2) females prefer males that have directly observed winning fights, or (3) winning previous fights indirectly improves a male's chance of being preferred by females. The last possibility may arise as a consequence of the "loser effect"; in many species when a male loses a fight his probability of losing subsequent fights increases. There are, however, no studies testing whether such a "loser effect" also influences male attractiveness. Here we show that male attractiveness and fighting ability are positively correlated in the house cricket, Acheta domesticus. Our experiment was designed so that females could not directly observe the outcome of fights, thus eliminating possibility (2) above. We then tested between possibilities (1) and (3) by making use of the fact that in some cricket species the "loser effect" can be eliminated experimentally by 'shaking' a male and stimulating the motor program for flying. We showed that in A. domesticus 'shaking' does affect the outcome of subsequent fights. Males that had won two previous fights were less likely to win a fight after being 'shaken' than when subject to a control treatment. In contrast, males that had lost two previous fights were more likely to win a fight after being 'shaken' than when they were not shaken. There was, however, no effect of 'shaking' on male attractiveness. We conclude that the "loser effect" does not alter the tendency for large, dominant males to be attractive to females. Instead, it appears that there are traits correlated with both fighting ability and attractiveness. One such trait is body size. Fight winners were significantly larger than losers and attractiveness was positively correlated with male body size.