A friend and I were recently watching a program about baboons and she mentioned that she heard of a baboon that has a heart on the outside of its body. Is there really a baboon in Africa with a heart on the outside of its body,  or was my friend pulling my leg?

–Anne, Harrisburg, PA, U.S.A.

Well, your friend was and was not pulling your leg. There is a species in Africa that is known as ‘the bleeding heart monkey,’ but I swear its all-important internal organ is exactly where it is supposed to be.

The Gelada (Theropithecus gelada) is often times called ‘The Gelada Baboon,’ although it is not a baboon at all (it gets this misnomer from being very close in appearance to baboons). Baboons are a species of primate in the genus papio. The gelada (no last name–like Cher) is a primate in the genus theropithecus and is the only living species in this genus.  That being said, the gelada and the baboon are closely related cousins (sort of like zebras and horses: zebras aren’t horses but they are equines and thereby related) and because of this relation, many scientists believe the gelada should be included in the papio family and yet other scientists believe it should remain in its own genus. Unlike any other primate, the gelada has the distinctive feature of an hourglass-shaped patch of skin on its chest. To the human eye, it looks very much like a window to the gelada’s heart, hence its handle, ‘the bleeding heart monkey.’ Although this patch of skin occurs on both males and females, the males’ patches may be more pronounced but it is the female’s that get to be studied.

The Lion Baboon - A male gelada

As geladas are 100% herbivores (i.e., vegetarians), unlike their baboon cousins, they spend most of their day in a sitting position foraging for grasses. Because of this sitting position, scientists believe the ‘bleeding heart’ patch developed as a genetic modification to their baboon cousins’ swelled buttocks: when a female baboon is in estrus, her buttocks swells and reddens, letting the males know she has not lost that lovin’ feelin’.  With female geladas, the ‘bleeding patch’ acts in much the same way- it reddens and becomes surrounded by fluid-filled blisters when in estrus. Scientists believe this genetic modification came about as, since the female gelada is in a sitting position for most of the day, if she’s in estrus- how are any of the males supposed to see her love signals? Hence, the ‘bleeding patch’ acts as the female geladas own ‘Bat Signal,’ letting the males know she is ready to mate.

Did You Know…?

• Because of the male geladas brilliant tuft of hair around its head, shoulders and tail, this creates a lion’s mane-like effect, which is why the male gelada is also known as ‘The Lion Baboon’
• Geladas live in matriarchal families known as tribes or troops
• The geladas live in the mountains of northern Ethiopia, with the highest population in the Simien Mountain National Park. They are found nowhere else in the world.
• To escape predators at night, the gelada creep over the cliffs edge and-literally- hang on to the rocky mountainside with their fingertips.

Author: Erin

Heading up AWF’s membership desk for the past eight years, Erin Keyes has amassed quite a bit of knowledge about Africa’s wildlife and unique wild lands. She’s also an expert on AWF’s membership benefits and programs. She started this blog to share what’s she’s learned and to give AWF supporters another forum for asking questions