Thursday, December 15


Obviously, to reproduce successfully, a female has to attract a sexual partner, but the consequences of anisogamy--that males are more mobile, have a higher sex drive, and seek multiple partners--means that this is a fairly easy task. This circumstance allows females an element of choosiness when it comes to purely sexual partnering.

In most species, females are only receptive to sexual advances when they are fertile, i.e., during a 'breeding season' or, in the case of non-seasonal breeders, as related to her own biorhythms. To be the target of a sexual advance, then, a female must signal that she is in breeding condition. Examples of physical signals of breeding readiness include the estrous swellings of the genitalia of many primates (e.g. Altmann, Hausfater & Altmann, 1988; Hrdy & Whitten, 1987) and the release of sex pheromones by other mammals, reptiles and insects (e.g. Crews, 1992, Thornhill & Alcock, 1983). In some species of amphibians and fishes, the key physical indicator might be as simple and direct as the bloated outline of the body when it is full of eggs (e.g. Rowland, 1994). These signals of breeding readiness can attract many males simultaneously-- just think of the randy males that arrive on the scene when a neighborhood cat or bitch is “in heat.”


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