Top 10 Animals with Sexual Dimorphism

Sexual dimorphism is the condition where there is a dramatic difference between sexes, such as color, size, ornamentation, shape, or behavior.

Sometimes, males and females look so different that you might mistake them for different species.

Usually, males appear more spectacular than females because, in the competition for mates, females prefer bigger and more elaborate males. They tend to select against males that are dull in color.

In human society, things are somewhat inverted. Females often wear more colorful and ornamented clothing, along with makeup. However, males are still generally larger in size.

The Top Ten

Triplewart Seadevil

It's a type of Anglerfish. This is probably the most dramatic example of sexual dimorphism - males may be several orders of magnitude smaller than females. The length of females is about 30 cm (12 in), while males measure only 1.05 cm (0.41 in). Males attach to females near the vent and live on them parasitically.

In the lower image, the arrow points to the tiny male, and the small letters read "parasitic male". You can see the proportion.
Peafowl

Peafowl include two Asian species, the blue or Indian peafowl from the Indian subcontinent and the green peafowl from Southeast Asia, as well as one African species, the Congo peafowl from the Congo Basin. These birds belong to the genera Pavo and Afropavo in the family Phasianidae, which includes pheasants... read more

This is the male (in the image). Females lack the prominent tail and have a subdued brown coloration. Nonetheless, females are still very beautiful birds.
Golden Pheasant

What you see in the image is the male. Females are much smaller and lack the ornamental crests, wattles, and long tails of males. Females display dull colors and resemble ordinary beige farm chickens.
Lion

The lion (Panthera leo) is a large cat in the genus Panthera, native to sub-Saharan Africa and a single isolated population in western India. It has a muscular, broad-chested body, a short rounded head, round ears, and a hairy tuft at the end of its tail. Adult males are larger than females and have... read more

You see the male in the image. Females do not have the prominent bushy mane.
Sage Grouse

It's a male in the image here. The male is much larger and appears more bizarre. He has two inflatable gular sacs that he uses to attract mates by inflating them.
Mosquito

The word "mosquito" comes from Spanish and means "little fly." Mosquitoes are small flying insects known for transmitting numerous infectious diseases. These include malaria, yellow fever, chikungunya, West Nile virus, dengue fever, filariasis, and Zika virus, making mosquitoes one of the deadliest groups... read more

Only females are bloodsuckers. Males are not and follow a different diet. Females have specialized blood-sucking mouthparts.
Mandarin Duck

Again, this is the male you see. Females do not have this rich coloration and differ in shape because they lack a crest and have a more ordinary bird tail.
Frigatebird

Males have a distinctive red gular pouch (also known as a throat pouch) - it's an area of featherless skin on the neck. Males inflate this pouch into a huge red balloon during the breeding season to attract females.
Orangutan

Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the genus Pongo, orangutans were originally considered a single species... read more

I am almost sure it's a female in the image. Male orangutans have enlarged cheek flaps and a throat pouch. More dominant males exhibit larger flaps.
Great Argus

In the image, you see (from left to right): female, male. There is a big difference.

The Newcomers

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Nilgai
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Capercaillie

The Contenders

Guppy

Male guppies are adorned with colorful spots and ornamentation, while females are grey. In the image here, the upper fish is the male. The other two are females.
Chicken
Mallard

This is the male - it has a green head. Females do not have the striking green coloration.
Mandrill

This is a male (in the image). The female Mandrill is much smaller and lacks the bright exotic coloring.
Green Anole

Green Anole, also known as Carolina anole, is a lizard species. Male anoles (shown in the image) have a retractable gular fold used to attract mates.
Blue Tit

Males are "more yellow" than females.
Spotted Hyena

Hyenas, or hyaenas, are carnivorous mammals belonging to the family Hyaenidae. With only four extant species, they represent the fifth-smallest biological family in the order Carnivora. Despite their small number, hyenas play a vital role as both predators and scavengers in their ecosystems.