Why do some monkeys have red bottoms

They also have extremely long canine teeth that can be used for self-defense—though baring them is typically a friendly gesture among mandrills. These are primarily terrestrial monkeys, and they move with long arms to forage on the ground for fruits, roots, and animals such as insects, reptiles, and amphibians.

Their cheeks have built-in pouches that are used to store snacks for later consumption. Though mandrills spend much of their time on the ground, they can climb trees and do so to sleep. Mandrills live in troops, which are headed by a dominant male and include a dozen or more females and young. These colorful primates are threatened. They are often hunted as bushmeat, and many Africans consider them to be a delicacy.

Mandrills are feeling the squeeze of spreading agriculture and human settlement—both are shrinking their rain forest homeland. All rights reserved. Common Name: Mandrill. Scientific Name: Mandrillus sphinx. Type: Mammals. Diet: Omnivore. Group Name: Troop. Size: 3 feet. Weight: 77 pounds. Size relative to a 6-ft man:. Before it gets detected by your eye, a single photon that penetrates a biological tissue like skin will randomly scatter within the tissue many times.

But it is important to consider that skin is more complex than the forest analogy. Skin is composed of many layers and contains pigments such as melanin, and this affects how photons scatter. This added complexity is the secret to the blue monkey butt. To understand how photons move through a complex tissue like skin, lets compare a red photon with a blue photon as it hits two tissue layers. If layers A and B were both white like milk , they would reflect red and blue photons equally and you would see both colors.

In the picture above, both the red and blue photons bounce scatter 4 times while they are penetrating the skin. But because the red photons travel a longer distance in between scattering events, they manage to penetrate both layers of skin. They do not make it past Tissue A before they emerge and hit your eye. Only the blue light makes it out and gets into our eyes.

Callus is just a thickened and hardened portion of the skin or soft tissue, especially found in those body portions which are or have been subjected to repeated friction, irritation, and pressure. Just like in our body, our feet are most likely to see calluses thickened skin found on the bottom of our feet, just on the bony areas that carry our weight. The same happens in the case of other monkeys and baboons as well.

When we refer to the hard red butt of baboons we term it as Ischial Callosities. This thickened callus Ischial Callosities provides cushioning for the monkeys when they seat to support their body weight.

The Ischial Callosities are composed of large blood vessels and lymphatic vessels that go deep into the skin layers. In fact, large arteries are also located in the superficial dermis just deep to the epidermis. We also know that the blood contains Hemoglobin.

These Hemoglobin molecules when bound to oxygen start to absorb blue-green light from the surrounding, and only reflect the red-orange light into our eyes. Thus, it aids in spreading the red hue and making the blood red in color. So, due to the presence of numerous blood vessels with smooth muscular walls, and the swelling nature of the butt, the red hue of the blood flowing through the vessels gives the portion of the butt its red to light pink color depending on the number of vessels and thickened nature of the Ischial Callosities.

Sexual Swelling in baboons is due to the filling and retention of blood, water, and other body fluids in the enlarged areas of genital and perineal tissues of the body, including the ischial callosities. This sexual swelling causes the external and internal genitalia to swell forming edema and thus giving it a red to pink colored appearance. So, the baboons that show swollen bottoms or swollen butt are actually due to the biological reason of Sexual Swelling.

Sexual Swelling is just a way to advertise the sexuality and mating readiness of the females to the males. This is because it indicates the time she is most fertile to reproduce.

It is noticed that after every 34 to 37 days time period female baboons show swollen bottoms or the so-called sexual swellings. And so, during these 14 days time period, she is biologically prepared to enter into her heat phase and follicular phase and perform ovulation.

Just after the 14 days time period, there is a rapid decrease in swelling size which is actually due to the rising progesterone levels in their blood. So, it can be clearly stated that when the swelling size increases, this indicates the increase of estrogen levels showcasing that the baboon is entering into her follicular phase from her first day of menstruation to the time ovulation occurs. The time when ovulation occurs as mentioned above is the most fertile reproductive phase as during this timeframe if the female mates with the male, then the chances are the highest for her in getting pregnant.

And, when the swelling size decreases, this indicates the increase of progesterone levels and decrease of estrogen levels showcasing that the baboon is entering into her luteal phase. During this timeframe of the luteal phase, if the female mates with the male, then the chances are the lowest to almost nil for her in getting pregnant. Individuals can show moderate-sized to larger-sized swelling.

And, the female baboons with larger swellings also have higher lifetime reproductive success because of their very good increase in estrogen levels. Males are often attracted to those females who have larger swelling, thus giving the females more mating options. It is to be noted here that only the Female Baboons have a red swollen butt or we can say red swollen bottom.