Mating strategies based on foraging ability: An experiment with grasshoppers

Abstract

Female mate choice and the benefits of this behavior are critical aspects of Darwinian sexual selection, but they are seldom documented because it is difficult to identify the male trait(s) that females may be seeking. We conducted experiments with grasshoppers (Melanoplus sanguinipes: Orthoptera, Acrididae) to examine this behavior. Males that feed more intensively and select a diet mix that permits greater food intake (food intake per body mass per time) in laboratory trials were preferentially selected by females. These better foraging males on average provide greater paternal investment (greater spermatophore mass) to the female, which increases her reproductive rate (eggs produced per body mass per time). However, paternal investment may not entirely explain female choice of better foraging males, because these males were still selected even if they had then food intake restricted or had been allowed to recently mate, which reduces spermatophore production. Furthermore, males change their mating strategy in response to female choice and the foraging abilities of surrounding males. Poorer for aging males attempt forcible copulation rather than displaying and allowing female choice. A male will facultatively switch between these strategies depending on the foraging abilities of the surrounding males. While females attempt to reject forcible copulation, forcible copulation reduces the frequency with which females successfully copulate with better foraging males. Therefore males that are less 'attractive' to females adopt alternative mating strategies to counter female choice which would exclude them from mating.