It is often argued that females with attractive partners should produce more sons because these sons will inherit their father's attractiveness. Numerous field and laboratory studies have addressed this hypothesis, with inconsistent results, but there is surprisingly little theoretical work on...

Carotenoid pigments can directly enhance the immune responses of vertebrates, and they are used by many animals to create ornamental color displays. It has been hypothesized that these two functions of carotenoid pigments are linked: animals must trade off use of carotenoid pigments for immune...

Male-biased dimorphism in body size is usually attributed to sexual selection acting on males, through either male competition or female choice. Brown antechinuses (Antechinus stuartii) are sexually dimorphic in size, and heavier males are known to sire more offspring in the wild. We...

The avoidance of familiar individuals as mates can act to maximize the benefits of polyandry or might help to minimize inbreeding in small or highly philopatric populations. As previous mates are also familiar, the effects of familiarity and mating history can often be confounded. Here, we...

Females increase their risk of mating with heterospecifics when they prefer the traits of conspecifics that overlap with traits found in heterospecifics. Xiphophorus pygmaeus females have a strong preference for larger males, which could lead to females preferring to mate with heterospecific...

Earlier arrival to reproductive sites of males relative to females (protandry) is widespread among migratory organisms. Diverse mechanisms have been proposed that may select for protandry, including competition for limiting resources (e.g., territories) or mates. In species with large variation...

Although the killing of unrelated young (usually designed as infanticide) has been typically considered a male behavior, recent research has shown that females may commit infanticide even more frequently than do males. In rodents and primates, female infanticide represents a strategy associated...

Females of most animal taxa mate with several males during their lifespan. Yet our understanding of the ultimate causes of polyandry is incomplete. For example, it is not clear if and in what sense female mating rates are optimal. Most female insects are thought to maximize their fitness by...