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Why Do Baboons Have Red Bottoms?

If you’ve ever visited an animal sanctuary (a zoo or an animal orphanage), there’s a high probability that you’ve spotted some monkeys and baboons with red butts.

Since it’s common for most people to wonder why these primates have red bottoms, I’ve decided to address the topic in this article.

After reading this informative piece to the end, you’ll know the specific primates with red bottoms, as well as the reasons and purpose of this unique body feature.

Why Are Baboons’ Butts Red?

When it comes to communication, primates have unique ways of communicating and expressing themselves. Surprisingly, the red bottom is an effective non-verbal communication method among these animals.

However, it’s essential to note that not all have red derrieres; only female baboons’ buttocks are red. Male baboons have pinkish butts that may appear red when observed from afar, but only females exhibit the actual red color.

Also read: Why Do Baboons Steal Lion Cubs? What Tactics Do They Use?

Reasons and Functions of the Red Butts in Female Baboons

The Main Reason For The Redness

Blood, water, and other bodily fluids fill and settle at the expanded portions of the vaginal and peri-urethral tissues of the body, particularly the ischial callosities, of female baboons.

This effect makes the external and internal genitalia swell, creating an edema (sexual swelling) that makes their bottom (where their genitals are located) expand/enlarge and have a red appearance.

Baboon with red butt and baby

Function and Purposes of The Red Butts

The purpose of the sexual swelling and its red appearance is to act as a non-verbal cue. This communication tactic notifies the male baboons that the females portraying this characteristic are ready to mate. It’s the primary reason why the redness and the swelling are called ‘sexual swelling.’

Exclusive Details Related to The Red Sexual Swelling of Female Baboons

Females exhibit sexual swellings, or enlarged red butts, every 32 – 37 days, lasting 14 days. This period starts after menstruation when the sexual swelling begins to expand gradually.

It indicates that the female baboon is in her fertile stage or cycle days and is biologically ready to become pregnant. Their estrogen hormones are at an optimum level during this period (the ovulation stage).

A reduction in the red swelling occurs after the 14 days elapse. It’s due to the decrease in estrogen and a rise in progesterone. When a female and male baboon mate during this period (the luteal stage), her chances of becoming pregnant are extremely low to nonexistent.

It’s vital to note that females with larger, red swellings have higher reproductive success. Therefore, it makes them more attractive as mating candidates by the alpha males; since they are considered more fertile and highly likely to bear healthy offspring.

Also read: Do Monkeys Eat Banana Peels? Do They Actually Eat Bananas?

Are There Other Monkeys With Red Butts?

Yes, other primates, besides baboons (Genus papio), have red butts. They include:


These monkeys (Mandrillus sphinx) are among the oldest and the largest, often confused with baboons due to their huge size. Like female baboons, female mandrills have red swellings in their rears, indicating they are biologically fertile, ovulating, and ready to mate.

A mandrill showing butt

However, unlike the baboons, male mandrills have swollen butts that appear shiny red, blue, or pink (or a mixture of all colors, commonly referred to as rainbow-like color).

This feature indicates that they have significant testosterone levels, making them rank higher and become more attractive and suitable mating candidates to females.


Popularly known as chimps (Pan troglodytes), these apes are not scientifically recognized as monkeys. However, female chimps share this unique feature (swollen red butts) with female baboons, indicating they are ovulating and ready to mate.

Japanese Macaques

Also known as snow monkeys (scientific name: Macaca fuscata) due to their habitats which are usually covered in snow; they are common in the northern parts of Japan, such as Shikoku, Kyushu, and Honshu.

Although all these snow monkeys have distinct red faces, despite their gender, only females have red butts serving the same purpose as those of the baboons (to indicate fertility and readiness to mate and conceive).

Rhesus Macaque

Scientifically known as Macaca mulatta, both genders of these monkeys have red faces and butts, but females have darker and swollen rears.

Surprisingly, both genders prefer to mate with those that exhibit a dark red color on their butts; hence the darker a male or female buttocks are, the more attractive and superior they are as a mating partner.

Celebes Crested Macaque

Celebes Crested Macaque

These monkeys (scientific name: Macaca nigra) have very short tails and black fur covering their huge body. It is believed that Celebes males also used to have rainbow-colored buttocks similar to the Mandrill males, but their butts are now pale red.

The female behinds’ have a dark red color when they are ovulating. Additionally, their sexual swelling significantly enlarges and becomes extremely red during mating.

Also read: How Strong is an Orangutan? (Much More Than You Think)

Why Do Monkeys Show Their Bottoms?

Let’s take a closer look at some of the main reasons why monkeys show their bottoms.

As A Sign That They Are Fertile/Ovulating

As previously stated, female monkeys and baboons have a red enlarged butt, referred to as ‘sexual swelling,’ which indicates that they are currently ovulating.

Therefore, they display their red bottoms; as a non-verbal way of showing that they are presently in their fertile phase.

To Attract Potential Mates

Since both genders of most monkey species, especially the macaques and mandrill monkeys, have red butts; they usually display their bottoms to attract/seduce mates of the opposite sex.

Since the redness of male butts is a sign of their high testosterone levels, the species use it to prove to their female counterparts that they are the ideal candidates to consider and prioritize when it comes to mating.

To Prove That They Have Superior Genes in Conceiving

According to recent studies conducted on primates, most male monkeys preferred females with significantly enlarged buttocks as they appeared to be more sexually attractive compared to those with medium to small ones.

Scientists researching chimpanzees called it the ‘inversion effect.’ When interpreted in the chimps’ language, it means that a female with a red and enlarged ‘sexual swelling’ has a higher probability of attracting and arousing plenty of males, especially the alpha, by indicating that she is ready for business!

Therefore, female monkeys and chimpanzees will always try to display their red ‘sexual swellings’ to prove that they have the best genes needed to mate, conceive and breed healthy offspring.

Since the law of the jungle dictates that the strongest one gets to survive, female monkeys use their reproductive powers (enlarged red, sexual swellings) to gain a competitive advantage over their less-endowed counterparts.

A baboon with red bottom

To Gain Respect and Special Favors

It seems that monkeys were aware of the inversion effect before scientists realized the phenomena. Females with more enormous red swellings have always flaunted their behinds, especially when a new alpha takes over a territory.

Since the females mating or bearing the offspring of a dominant male receive special favors (such as feeding priorities) compared to other members, they will try to prove that they deserve to be included in the VIP class by flaunting their bottoms to the King of the territory.

When a female captures the alpha’s attention, her social rank significantly rises. She automatically gets to enjoy special favors, such as being among the first members to feast on a meal before the other inferior monkeys are allowed to eat.

Final Thoughts

The world is full of wonders, and the significance of the red bottoms among baboons and the specific monkey species mentioned above is one of them.

It’s marvelous how such a fascinating and unique body feature is essential to the lives and survival of these primates. It proves that all creations were meant to serve their specific purpose.

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