9 of the Most Dramatic Examples of Sexual Dimorphism

A male and female Mandarin duck
Mandarin ducks display significant sexual dimorphism. The male (left) has a bright red beak and colorful plumage, while the female's colors are more muted.

Mark L. Stanley / Getty Images

Ever wonder why males and females of the same species can sometimes look radically different from each other? It's all thanks to a condition known as sexual dimorphism, which is generally triggered by the process of sexual selection through competitive mating.

Sexual dimorphism can manifest in many fascinating ways — size, coloration, behavior and the presence of secondary sex characteristics like tail feathers, breasts or antlers. Here are nine incredible examples of sexual dimorphism in the animal kingdom.

1. Mandrills

A male and female mandrill
Mandrills are one of nature's most extreme examples of sexual dimorphism.

Curioso / Edwin Butter / Shutterstock

The mandrill is widely considered to be the most sexually dimorphic mammal species. When you examine the images of the male and female mandrills, one of the first things you'll notice is that males exhibit a more vibrant coloration on their faces and behinds.

However, if you were to encounter one of these majestic primates up-close, you'd quickly realize that the most dramatic difference between their sexes is their size. While the average female mandrill weighs about 27 pounds, some male mandrills can weigh up to 82 pounds.

2. Triplewart Seadevil Anglerfish

A diagram depicting the size difference between female and male triplewart seadevil anglerfish

Commons sibi / Wikimedia Commons / CC BY-SA 3.0

Living as deep as 6,600 feet below the ocean's surface, these anglerfish are arguably the world's most extreme and downright bizarre manifestations of sexual dimorphism.

The females of this species measure about a foot in length, while males barely reach half an inch. This dramatic disparity in size is largely due to the species' parasitic mating practices.

3. Pheasants

A male and female Ringneck pheasant

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In addition to their larger size, male pheasants are characterized by their colorful, decorative plumage, ornamental wattles and extra long tails. Female pheasants, in contrast, are quite minimal in their appearance.

4. Elephant Seals

A male and female elephant seal

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These pinnipeds are named for the males' large proboscises that slightly resemble an elephant's trunk. Their proboscis can emit incredibly loud roars during mating season.

5. Orange Tip Butterflies

A male and female orange tip butterfly

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These butterflies are named in honor of the specific sexual dimorphism they exhibit: the orange tips found on the forewings of the males.

6. African Lions

A male African lion and a female African lion with her cub

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The iconic bushy manes of African lions are highly linked to the process of sexual selection, and studies have shown that lionesses are more likely to pick a mate that boasts a dark, thick mane.

7. Mandarin Ducks

Male and female Mandarin ducks

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While both sexes of the Mandarin duck possess beautiful plumage, the males of this species are especially striking with their red bills, pronounced crests and array of colorful feathers.

8. Orangutans

Male and female orangutans

Sergey Uryadnikov / GUDKOV ANDREY / Shutterstock

As they reach sexual maturity, male orangutans begin to develop enlarged cheek flaps that are meant to exhibit their dominance. When there is more than one male within a family, the more dominant male will exhibit more exaggerated cheek flaps.

9. Peafowls

Male and female peafowls

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Peafowl are among the most well-known and gorgeous examples of sexual dimorphism. While males (peacocks) sport a flamboyant and iridescent "train" of tail feathers that can open up in a grand display, females (peahens) possess a significantly more subdued appearance.