Male dominance and immunocompetence in a field cricket

Female preference for dominant males has been found in many species, and it is generally thought that winners of male-male competition are of superior quality. Success in contests probably depends on male condition and overall health. Thus, females could avoid infection and gain genetic benefits in terms of more viable offspring by mating with dominant males. In the present study, we tested whether dominant males of the Mediterranean field cricket, Gryllus bimaculatus, had higher immunocompetence than did their subordinates in experimental trials. We found that dominant males had better immune defense, as indicated by significantly higher encapsulation rate and lytic activity, than did subordinate males of the same size. Dominant males were also more successful in obtaining matings, but this was measured nonindependently of dominance status. Our results suggest that a male's dominance status and success in fights may indicate his immunocompetence to females.