Amazing adaptations of the Angolan colobus

Adaptations. They are all around us. Some are more visible, such as the cheek pads on a male orangutan, and some are not as visible, such as cheek pouches in monkeys or a giant panda’s pseudothumb. But every single adaption serves a purpose for that individual animal. And if you pay attention, you will notice that all of an animal’s adaptations work together to help that animal survive and reproduce.

Now I could talk all day about the numerous adaptations the animals here at Zoo Atlanta, have but today I am going to focus on my favorite species, the Angolan colobus monkeys. Now if you recall, my last blog was also about our colobus monkeys and how the offspring are born completely white. While that is one of their more well-known adaptations, today we are going to be talking about two of their other major adaptations. The first one is going to be another well-known adaptation, and that is their thumb, or lack thereof. It is often a misconception that colobus monkeys don’t have thumbs. This is not the case, but their thumbs are just really small and do not provide any function. I don’t know if you have ever injured your thumb, but if you have, you quickly realize how important your thumb really is to everyday life. So why in the world would an animal evolve not to have one that is functional?

Having a really small thumb allows Angolan colobus to swing through the trees easier and more efficiently by having the four fingers act almost like a hook. Since colobus monkeys are considered the most arboreal (tree-dwelling) monkey species, they spend a lot of time swinging through the trees. One thing I have learned in my time working with animals is that often times, an adaptation doesn’t just have one purpose or reasoning behind it. Because they spend most of their time in the trees, it would make sense that their diet mostly consists of leaves. Leaves are obviously very easily ripped off branches. So easy that one doesn’t necessarily need a thumb to do it. So even though to most primates, the lack of a functional thumb would be detrimental to them, it is not to a colobus, as they don’t really have a need for it.

The second adaptation we are going to talk about today is one that is a little lesser known and one that is not as visible. As mentioned above, a colobus monkey’s diet mostly consists of leaves. Since monkeys are primates, that means that most of them have a very similar digestive system to us. And if you didn’t know, humans’ and monkeys’ digestive systems are not designed to digest that many leaves every day. So how are colobus able to do it? Well they have developed a special digestive system that is actually very similar to that of cows. In order to breakdown the leaves and get the nutrients from them, the body has to ferment them. So, their stomach has evolved to do just that. Now I won’t get into all the science that goes into the process, but to sum it up, their stomach contains a bunch of microbes that ferment and break down all those leaves which then allows their body to absorb the nutrients. This process does take more energy than normal digestion does, though. Because of this, colobus are going to spend more time resting than most monkeys do.

Learning about and studying an animal’s adaptations is something that I find extremely interesting. My favorite part is seeing all those adaptations tie in together and work with each other, just like the ones we just talked about. Because they spend so much time in the trees, they have developed a way to move through the trees easier and have developed a way to eat the food source that is most available: leaves. So even though a small thumb and a specialized digestive system don’t seem related, they are. So next time you are at the Zoo, see if you can spot some adaptations!
Sonny Christopher
Keeper I, Primates