Top 10 Animals with Sexual Dimorphism

Sexual dimorphism is the condition where there's 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 look more spectacular than females because in the competition over mates, females prefer bigger and more elaborate males and females select against males that are dull in color.

In human society things are inverted - usually females wear more colorful and ornamented clothes, and makeup. Males are still bigger in size though.

The Top Ten

1 Triplewart Seadevil Triplewart Seadevil

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

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), of males - 1.05 cm (0.41 in).
Males attach to females near the vent and live on them parasitically. - Metal_Treasure

2 Golden Pheasant Golden Pheasant

What you see in the image is the male. Females are much smaller and have no ornamental crests and wattles, and long tails. Females are with dull colors and look like the most ordinary beige farm chicken. - Metal_Treasure

3 Peafowl Peafowl The peafowl include two Asiatic bird species (the blue or Indian peafowl originally of India and Sri Lanka and the green peafowl of Myanmar, Indochina, and Java) and one African species (the Congo peafowl native only to the Congo Basin) of bird in the genera Pavo and Afropavo of the Phasianidae family, more.

This is the male (in the image).
Females have no the prominent tail. They have a subdued brown coloration. Females are still very beautiful birds though. - Metal_Treasure

4 Lion Lion The lion is one of the big cats in the genus Panthera and a member of the family Felidae. The commonly used term African lion collectively denotes the several subspecies in Africa.

You see the male in the image. Females don't have the prominent bushy mane. - Metal_Treasure

5 Sage Grouse Sage Grouse

It's a male in the image here. The male is much bigger and looks more...bizarre.
The male has two inflatable gular sacs that are used to attract mates - the male just inflates them. - Metal_Treasure

6 Mosquito Mosquito Spanish for "small fly," mosquitoes are flies that have been known to cause various diseases . A sample of diseases caused by mosquitoes: malaria, yellow fever, Chikungunya, West Nile virus, dengue fever, filariasis, Zika virus .

Only females are bloodsuckers! Males are not. They are on a different diet.
Females have different and very specialized blood-sucking mouthparts. - Metal_Treasure

7 Mandarin Duck Mandarin Duck

Again, this is the male you see. Females have no this rich coloration. Females are dull and have a different shape because females don't have a crest and the tail is different, i.e. ordinary bird tail. - Metal_Treasure

8 Frigate Bird Frigate Bird

Males have a distinctive red gular pouch (aka 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 / courtship to attract females. - Metal_Treasure

9 Orangutan Orangutan

I am almost sure it's a female in the image. Male orangutans have enlarged cheek flaps and a throat pouch. More dominant males have bigger flaps. - Metal_Treasure

10 Great Argus Great Argus

In the image you see (from left to right): female, male. Big difference. - Metal_Treasure

The Contenders

11 Guppies Guppies

Male guppies have colorful spots and ornamentation while females are grey in color.
In the image here, the upper fish is the male. The other 2 are females. - Metal_Treasure

12 Nilgai Nilgai
13 Mallard Mallard

Yes, these are very familiar ducks - LightningStrike

This is the male - it has a green head. Females don't have the great green coloration. - Metal_Treasure

14 Chicken
15 Mandrill Mandrill

This is a male (in the image). The female Mandrill is much smaller and has no bright exotic coloring. - Metal_Treasure

16 Green Anole Green Anole

Green Anole, aka Carolina anole, is a lizard and male anoles (in the image) have a retractable gular fold that is used to attract mates. - Metal_Treasure

17 Blue Tit Blue Tit

Males are "more yellow" than females. - Metal_Treasure

18 Capercaillie
19 Spotted Hyena Spotted Hyena Hyenas or hyaenas are any feliform carnivoran mammals of the family Hyaenidae /haɪˈɛnᵻdiː/. With only four extant species, it is the fifth-smallest biological family in the Carnivora, and one of the smallest in the class Mammalia.
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