Why do Baboons Have Red Bottoms?

Baboon monkeys are truly fascinating creatures for many reasons. For one, they do not have tails and, unlike their other monkey cousins who swing from tree to tree, they live mostly on the ground.

However, these traits are greatly overshadowed by this monkey’s peculiar derriere — specifically, by its shocking red color. Join us as we dive deeper into the signature red bottoms of the baboons.

Why Do Baboons Have Red Bottoms?

The red bottoms that baboons are so popularly known for are actually an indicator used for mating. That’s right — the colored buttocks that set these monkeys apart are actually an indicator of fertility.

Only female baboons have red bottoms. Male baboon buttocks may appear pinkish but never totally red. At the same time, female baboon butts aren’t always red.

Instead, the color of the female baboon’s butt can be indicative of what stage of their fertility cycle they are in.

When the female baboon’s bottoms swell and turn red, it is usually an indication that they are fertile and ready for mating.

Aside from turning red, the baboon’s bottoms also swell four to up to almost ten inches (roughly around 10 to over 25 centimeters) which further emphasizes their buttocks.

What are the Functions of a Baboon’s Red Bottoms?

While these red bottoms certainly are amusing to look at, this is not the only function that this unique derriere serves.

These buttocks actually serve several functions in the baboons’ lives that are often overlooked.

Indicator of Fertility

As mentioned above, a female baboon’s butt will turn red as an indicator of her fertility. This phenomenon occurs once each month and will last around 10 to 20 days at a time. 

When a baboon’s butt swells and begins to turn visibly red, it signals to the male baboons that she is in a specific stage of her monthly cycle and biologically ready to conceive

However, while a female baboon’s body may be ready to conceive, the baboon herself may not be receptive to mating advances all the time especially if she has just given birth.

Most baboons usually take a break for around one year to focus on raising their newborn infant.

During this time, multiple cycles may occur wherein the female’s bottom will appear red and swollen but she will not receive any invitations to reproduce.

Indicator of Chances of Conception and Infant Survivability

It was also once believed that the bigger and redder the female baboon’s buttocks were, the better the chances for this specific baboon to conceive and successfully raise their young past infancy.

It was also believed that females with bigger bottoms will not only begin mating at an earlier age, but will also be able to produce more infants all of which have a higher survival rate as opposed to those with smaller buttocks.

However, recent studies done in 2015 have shown that this is simply not the case. Many factors affect the female’s ability to conceive and successfully rear her young.

These include ranks within the troop, post-partum cycles, and so on.

As a result, the size or amount of swelling that occurs in the female’s bottoms during her fertile period is no longer used as an indicator for conception success and survivability of infant baboons.

Measure of Attractiveness

Why do Baboons Have Red Bottoms?

Another once accepted belief around the buttocks of the baboon is that male baboons were more attracted to females with bigger and brighter bottoms.

The size and color of the female baboon’s bottoms were believed to function as an aphrodisiac to the male members of this monkey community and served as a measure by which they gauged the attractiveness of a potential mate. 

In short, the bigger the better.

This theory has been debunked as of late as studies have shown that male baboons preferred to mate with women who have had more post-partum cycles since giving birth. 

The same study suggests that males count females’ post-partum cycles and avoid making advances towards mating if they feel it is “too soon.”

What Makes a Baboon’s Bottom Red?

A female baboon’s butt swells and turns red due to the retention of blood and body fluids in this region as a result of sexual swelling.

Sometime around the 37th day of their fertility cycles, the female baboon may experience sexual swelling that causes blood, water, and other body fluids to be retained in the reproductive areas of the baboon’s body. 

This retention of fluids gives the baboon’s bottoms the flush red appearance that this monkey is so well known for. This event is also what causes the baboon’s bottom to swell to a much larger size than usual.

After this period in the female baboon’s fertility cycle, her bottom shrinks back to its normal size and goes back to its usual color.

Can a Baboon Voluntarily Make Her Bottom Red?

While the reddening and the swelling of a baboon’s bottom are mostly controlled by the monkey’s fertility cycle, there are rare occurrences wherein the baboon can trigger this mechanism in a form of self defense or preservation.

Whenever a new male dominates the troop, one of its main goals is to dominate the female population by mating with them. 

It is also often in their best interest to kill all infants sired by the previous dominant male in order to assure that his genes dominate the next generation.

Some may even go as far as to cause pregnant baboons to terminate the pregnancy by miscarriage. 

In order to protect their infants and unborn babies, some female baboons may cause their buttocks to swell and appear red in order to feign fertility to give the male the chance to mate with them and prevent the male from killing their infants.


The red bottoms of the baboon may appear to most as just a unique physical quirk. However, it is actually an indicator of a great social function in the world of the baboons.

The distinguishing red bottoms of the baboon serves an important function in the mating system of these monkeys. In addition, they can serve as a preservation technique that saves the lives of their most vulnerable members — their infants.