Abstract
Same-sex sexual behavior (SSB) is widespread among animals and is often treated as an evolutionary anomaly or mistake. An alternative view is that SSB occurs because individuals have broader or more permissive "mating filters." A broader filter means directing courtship toward anything that resembles a potential mate, while a narrower filter means having stricter criteria about when to court. Broader filters help ensure animals do not miss out on mating opportunities. However, it may be advantageous for individuals to narrow their mating filters under some conditions, such as when the costs of courtship increase because courting individuals are in poor condition. We examined whether mating filters, and the expression of SSB, is condition dependent in the Pacific field cricket (Teleogryllus oceanicus). When males were in poor condition (because they were reared on a poor diet), they courted other males less. However, condition did not influence courtship toward females. This finding provides evidence that animals can decrease their expression of SSB by flexibly narrowing their mating filters when in poor condition. Our results demonstrate the benefits of a mating filters approach to studying SSB-rather than being a mistake or an anomaly in need of special explanation, SSB may be better viewed as a consequence of flexible, condition-dependent changes in mating behavior. Such an approach can be applied to other contexts where behavior is directed toward unintended targets. We emphasize that our results, like other studies of SSB in nonhuman animals, tell us nothing about sexual identities in humans.