Male courtship effort determines female response to competing rivals in redback spiders

When males compete with rivals in the presence of females, there may be a trade-off between courtship and competition. We examined responses of female redback spiders, Latrodectus hasselti, to courtship from rival males under different competitive contexts. We paired size-matched males with females, and assessed correlates of male mating success. We compared these results to published data between females and single males or size-mismatched rivals. Size-matched males attempted copulation after a brief courtship, a strategy similar to smaller, ‘sneaker’ males in size-mismatched competitions. We also found context-dependent differences in female remating frequency and premature cannibalism. In size-mismatched and single-male trials, females prematurely cannibalized smaller males and males that mated quickly, but this was not the case when rivals were size-matched. However, in both types of competitive trials, males that mated rapidly paid a fitness cost. The courtship duration of the first male to mate was inversely related to the number of copulations that females accepted from that male's rival. Thus, females use premature cannibalism to reduce the paternity of males that minimize investment in courtship if they are clearly distinguishable from their rivals (mismatched context), but they allow males to continue to compete if they are similar in quality (matched context). In both cases, biases in female remating behaviour favoured males that invested in courtship. We conclude that female reproductive behaviour partly depends on the relative size of competing males, but that male fitness depends heavily on investment in courtship.