Gift carrying in the spider Pisaura mirabilis: nuptial gift contents in nature and effects on male running speed and fighting success

► We examined ecological costs of nuptial gifts in the spider Pisaura mirabilis. ► Gift-carrying males are frequent in nature, and their gifts contain edible prey items. ► Thus, nuptial gifts are possible honest indicators of male foraging success. ► Gift carrying reduced male running speed, but did not affect a male's fighting success in male-male contests. ► This is the first demonstration of a transportation cost for nuptial gifts in an arthropod.