Male–male contests in the hermit crab Pagurus filholi: many males do not initiate contests

Abstract

To examine whether solitary males that had been single in the field are less active in male–male contests than those had been paired in the field in the hermit crab P. filholi, we conducted a laboratory experiment of male–male contests to compare the behaviors of challenger males that had been found not paired in the field (N-male), or had guarded other females in the field (G-male). We introduced a challenger male and a guarding pair into an experimental container and observed the behaviors of challenger males. N-males showed a significantly lower frequency of initiating contests than G-males. Time to initiate contests in N-males was longer than that in G-male. Difference in body size between male contestants significantly affected the time to initiate contests, contest duration and contest outcome, but female quality did not affect these variables. We suggest that solitary males of P. filholi in the field would not be always active for competition for mates, which will decrease intensity of sexual selection in this species.