Professor Allen Moore explains that because females have a limited number of offspring compared to males they are slightly more discriminating in their choice of mate.

Mate-choice is an interesting area of study, because it turns out that in most species it isn’t just two individuals coming together and therefore they mate. It turns out that in many different species, females will choose which males they are willing to mate with, and that is called mate-choice. And the reason that we think this occurs, is that females have a limited number of offspring they can produce compared to males who can fertilize an unlimited number of females. So for females, it costs more to reproduce and they are slightly more discriminating in who they will mate with, whereas males will mate with just about any female they run in to. So mate-choice is where (typically) females discriminate among different males and find males that are slightly better than average, or more compatible with what they are interested in, in terms of what makes a good mate. What makes a good mate typically depends on the species you study.

mate choice, mating, species, males, female, allen, moore