Sexual Dimorphism

Sexual dimorphism describes differences in the physical characteristics of the two sexes (beyond sex organs)

  • These differences may be subtle or exaggerated, and include size, colours, markings and behaviours

Sexual dimorphism has evolved as a result of differential mate selection in males and females of a species

  • Exaggerated traits (ornaments) are more likely to attract female attention, despite increasing exposure to predators
  • Over many generations, these traits have become more pronounced, leading to marked differences between sexes

Examples of sexual dimorphism can be seen in a number of animals:

  • Many species of birds show clear differences between males and females of the species (e.g. peacock and peahen)
  • Male and female deer can be differentiated by the presence of large antlers on the male stags
  • Even humans demonstrate clear sexual dimorphism (e.g. facial hair and other secondary sex characteristics)

Sexual Dimorphism in Birds

sexual dimorphism