Sexual dimorphism: what it is and examples - Summary

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You may have noticed that animals have differences that identify them as males and females. This is known as sexual dimorphism and it is an indispensable mechanism for reproduction and population dynamics. Such differences can occur in coat patterns, change in coloration, change in the size of structures such as antlers, or even in sound patterns. But why does sexual dimorphism occur? Is it really necessary if the sexual organs already exist?

In this Green Ecologist article we inform you about it by explaining what is sexual dimorphism and examples of this. The phenomenon also occurs in humans, so you will find it even more interesting.

What is sexual dimorphism

Sexual dimorphism refers to the physical differences of the organisms of a same species for sex differentiation, that is to say, between male and female, but they are different from those that the sexual organs already present.

Although sexual dimorphism is more common in animals, it is important to emphasize that in the plant kingdom there are also some cases. Plants are usually monoecious, meaning that they are males and females on the same plant, but some species have separate males and females. In certain cases there is usually sexual dimorphism, presented in the size and height of the plants.

Dimorphism begins to express itself with the arrival of the sexual maturity of an animal. This dimorphism serves so that the organisms of the opposite sex identify competent partners and sexually available.

Among the factors that give rise to this differentiation are the genetic information that is expressed in sexual development and the environmental factors on which the animals depend, where seasonality indicates to the animals that they are ready to show themselves as competent and available.

These signals are essential for sexual selection, in order to identify fertile couples and with whom a relationship is created. genetic recombination originator of suitable offspring. The dimorphism process can generate deterrence, or disappointment if it is not successful, in the opposing organism in order to modify its behavior. This is how dimorphism is also a type of communication between animals.

We advise you to read about the Playback function: what it is and why it is important.

Types of sexual dimorphism

Within sexual dimorphism we can find different types:

  • Sexual dichromism: difference in color, usually in more striking versions, to attract the opposite sex. Females tend to prefer the more showy males.
  • Sexual dimorphism: difference in the shape of the body or of any of the appendages, aimed at specific reproductive and gestational activities. For example, male crabs have a larger pincer to hit the ground and attract females through vibrations.
  • Sexual Dimegetism: difference in sizes, as a differentiating quality in polygynous species where males have to compete for females for their harem. In some species, large females represent better fertility, giving it an advantage when selected.
  • Sexual cycling: difference in sound patterns. In some groups such as amphibians and birds, song is important for courtship. In birds, this song denotes the health of the specimen, thus attracting the male to the females.
  • Sexual defamation: difference in intensity and light patterns. It can be used to attract the opposite sex, as adult female fireflies do, or to scare off threats, which is the case with larval-stage male fireflies.
  • Sexual diolpism: difference in defense appendages, especially in females to defend their nest or habitat.
  • Sexual dimorphism of the brain: differences in the behavior of animals, whether sexual behaviors or to protect their offspring. They occur due to structural changes at specific sites within the brain, where hormones such as estradiol also play an important role.
  • Behavioral sexual dimorphism: other animals that do not have such advanced cephalization develop their behavior with responses to chemical or visual signals. They may also have differences in their sexual behaviors.
  • Dietary sexual dimorphism: differences in feeding behavior, as in the case of sexual dimorphism in lions. The females are the ones who hunt the food while the males wait.

Examples of sexual dimorphism

Finally, we have just clarified this concept with some easy examples of sexual dimorphism:

Human sexual dimorphism

The human has a marked sexual dimorphism that begins to manifest itself from puberty and is what we recognize as sexual attractiveness. Although each person has their tastes and today there are many factors that come into play, biologically speaking there are differentiating modifications and standards between men and women. Women begin to accumulate fat in the thighs, hips and buttocks, while generally men are larger, usually 5 to 13% more. This proportion in size is also visible in hominoid monkeys. Another important trait, which is also common for sexual dimorphism in mammals, is the development of visible mammary glands.

Here you can get to know Mammals better: characteristics, types and examples.

rooster and hen

Sexual dimorphism in birds is presented by the presence of having more colorful plumages. This is the case of the sexual dimorphism of the rooster and the hen, where the first has more striking colored feathers, in addition to being larger than the hen, with spurs on the legs and high ridges on the head. They also present sexual cyclagism, as the rooster crows and the hen does not.

Learn more about the Characteristics of birds and Classification of birds by reading these other posts

Beta fish

Beta fish are a clear example of sexual dimorphism in fish. Males have showy tails with fiery colors and large veil-like sizes. Females show breeding stripes, indicating that they are ready to breed, and their tails are much shorter than those of males. They also have dimorphism in their behavior, where the males fight violently among themselves. In the process of courting the female, they swim around her to expose their impressive tails.

Learn with this other article more about the characteristics and Classification of fish.

Praying mantis

Sexual dimorphism in invertebrate animals is highly developed and, in fact, homomorphism does not exist. An excellent example are the Praying mantis. After copulation, the females kill the males and then eat them. Here we have a case of sexual dimorphism of behavior. Even males show a modification in behavior. There is also dimorphism of sexual digmemetic, as the female is larger. If this curious animal surprises you, don't miss this other post about the question: Is the praying mantis poisonous?

You can learn more about this other group of animals, to which the mantises belong, by reading this article on the Classification of insects.

If you want to read more articles similar to Sexual dimorphism: what it is and examples, we recommend that you enter our Biology category.

  • Fanjul, M. (2013) Ecological neurobiology. Mexico City: Siglo XXI Editores
  • Obeso, J., and Retuerto, R. (2002). Sexual dimorphism in holly, Ilex aquifolium: Cost of reproduction, sexual selection or physiological differentiation ?. Chilean journal of natural history, 75(1), 67-77.
  • Martínez, M., Navarro, F., and Martínez, S. (2013) Development of sexual dimorphism in the brain: the origin of identity and sexual behavior. Ibero-American fertility magazine. 30, 12-17. Available at
  • Camargo, M. (2012) Sexual dimorphism and deviation in the proportion of the sexes in preimplantation embryos. CES Veterinary Medicine and Animal Husbandry, 7(1), 101-115. Available at
  • Beingolea, O. (1987) The Lobster Schistocerca interrita on the north coast of Peru. Peruvian Journal of Entomology. 35-40. Available at
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