High motivation enables smaller contestants to win the contests in fiddler crabs (Brachyura, Ocypodidae)

Abstract

We observed the outcomes of fights of smaller contestants against larger opponents during male-male contests in Uca annulipes (H. Milne Edwards, 1837), Uca bengali Crane, 1975, and Uca rosea (Tweedie, 1937). Smaller contestants won 30, 31 and 37% of the contests in U. annulipes, U. bengali and U. rosea, respectively, regardless of body size disadvantages. Smaller contestants won when body size asymmetries were lesser, but took a longer time to win the contests, while with greater size-asymmetries, smaller ones lost the contests in a short time. In U. bengali and U. rosea, most of the smaller winners were residents (burrow owners), but not in U. annulipes. This study shows that longer fighting duration or high motivation enables the smaller contestants, especially the residents, to overcome their inferior fighting ability and win contests against larger opponents.