Monday, March 24, 2014

Pongo, the weird cousin in the great ape family

Last post I talked about the differences between Bornean and Sumatran orangutans. But what makes orangutans different from all the other great apes? There are 4 extant great ape genuses: humans (Homo), chimps (Pan), Gorillas (Gorilla), and Orangutans (Pongo). Out of all these, the orangutans split off from the rest the earliest, and are genetically the least related to humans. In many ways, they are the weirdest of the great apes!

To start, they are the only remaining ape species native to Asia. All the other great apes are found only in Africa (except for humans, which today are a global species – but we originally evolved in Africa). Note that I say ‘remaining’ ape species. Millions of years ago, apes were rampant across the old world, including many species in Asia. At some point, most of these species went extinct, and only the orangutan and gibbon line survived the present day.  Were any of these species ancestral to orangutans, and if so which ones? No one really knows for sure, but some of the skeletal remains we have found in Asia show some morphological similarities to Orangutans. Search Sivapithecus if you want to find out more. Interestingly, there was a gigantic species of ape called Gigantopithecus living in Asia until fairly recently (and by fairly recently, I mean thousands of years ago). Humans were already around, and may have run into this other ape creature – in fact, some people think this may be the origin of the ‘Yeti’ or ‘Sasquatch’. Maybe when humans and Gigantopithecus coexisted long ago, humans lived in fear of this creature and shared stories to each other about it; through the retelling of these stories from generation to generation, the creature survived in our memories and into legend, even after it became extinct. Of course, there are always those who insist bigfoot/yeti/sasquatch hasn’t gone extinct, but let’s not get into that. 

Orangutans are the most arboreal of the great apes. Chimpanzees, Bonobos and Gorillas spend a lot of their time in trees, but they also spend an extensive amount of time on the ground, where they move around by knucklewalking. This is probably a big reason why orangutans have been the least studied great ape; it’s a lot harder to find them, follow them, and take date on them, if they’re constantly up high in the branches, out of view. Humans are obviously the least arboreal of the five species of great ape, given that we’re bipedal and spend virtually all of our time on the ground. Orangutans however, spend almost all of their time up in the trees. They are very well adapted for it, having long arms and long legs for reaching across gaps to grab branches, and they have very long fingers and opposable thumbs on both hands and feet, which allows them to firmly grasp the branches and trunks they use to move around.  It’s almost like the have four hands rather than two hands and two feet, allowing them to have multiple points of contact to the trees that they use to move around, which makes it safe for them to be up so high. 

They are masters at this kind of locomotion, being able to ‘polevault’ from tree to tree by bending the trunks and swinging to an adjacent tree, as well as brachiating their way throughout the canopy. Primatologists who study orangutans have traditionally thought that only the flanged males come to the ground often; however, a recent study which used a collection of camera traps distributed over a study site, found that all age-sex classes of orangutans come to the ground fairly often. Personally, I’ve seen females come down to the ground as well, but only a handful of times (and one of the females was traveling together in consortship with a flanged male, so perhaps she felt safe enough in his presence to come down). We still don’t know if this is a universal thing among all groups of orangutans, or something that varies from site to site…maybe they all do this, but just not often in the presence of people. This just shows that there is still a lot to learn about orangutan behavior.

In contrast to all of the other great apes, which are extremely social creatures with complex social dynamics and networks, orangutans spend the majority of their time alone. They do interact with other individuals from time to time, so they could be described as solitary but social. There is not much long-term social bonding. Usually mothers and their offspring will remains in association for a long time, and will overlap in home range, but eventually their social bonds weaken and they end up living independent lives. The relationship seems to last longer with daughters, as male offspring will usually migrate out of their home range into a new area. The consequence of this is that in a particular area, a lot of the females will be related, but few of the males are. Often times we see that when orangutans form a party (which is the technical term for when two or more orangutans interact and travel with each other during the course of a few hours, a day, or longer), they are all female and related.  Sociality also depends vastly on fruit availability. If fruit availability is low, they will tend towards solitude to avoid competition. If fruit availability is high, they will aggregate in the feeding trees more often and tolerate each other’s presence; there is enough food to go around and the benefits of social interaction outweigh the costs of sharing the food supply. Of course, all of these facts is what we has been traditionally written about in the orangutan literature. 
More recently, researchers are starting to find that perhaps orangutans are more social than we think. Definitely not as social as other apes, but sociality is still a very important part of orangutan dynamics. 

Flanged males (If you’re wondering what flanged males are, I’ll explain it in the next post!) prefer traveling alone, unless they are in consortship with a female; they do not under any circumstances associate with any other males, and will get aggressive upon encountering others. Unflanged males tend to avoid other males, but sometimes they will form bachelor squads with other unflanged males. 

This is just the tip of the iceberg when it comes to orangutans. What I mentioned before about flanged/unflanged males is a very interesting dynamic among orangutans, and I’ll be diving down into that on the next post. 

Wednesday, March 19, 2014

What is an orangutang? I don't know, because this post is about orangutans.

Before I begin:  I’ve been away from working on this blog for a while. I started writing this next series of posts a couple months ago, but I just never posted them. I’ve been busy up at camp and 
have had to shift my efforts elsewhere. My time here for the last year has been great . I’m not going to be here forever though, and I don’t want to leave without sharing my experiences with all of you. So I’m going to work extra hard to get at least one post out a week. But moving on…

If you’re reading this, you’re probably well aware that we’re all about orangutans here. So here’s a question…what is an orangutan? A simple question perhaps, but when it comes to simple questions, the answers are rarely as simple or as obvious as we think. As an example, ‘why is the sky blue?’ is a simple question, but to answer it you have to go neck deep into the physics of light and refraction…which means that for most of human history, a simple fact that every 
person who ever lived has been well aware of (that the sky is blue) could not be truly explained until the last 100 years.  

‘What is an orangutan?’ is a rather open-ended question, and has answers on a multitude of levels. So let’s start with something basic: what does the word even mean? Well first of all, the spelling. It's not orangutang. That's just a weird word some redneck said one day, and it somehow spread enough that a lot of people think it's how you spell and/or say orangutan. Actually, it might even be because of that fake juice drink that is supposed to taste like oranges, but really just tastes like like sweat, sugar, and food coloring mixed together. I'm talking about you, Tang. You remember the commercials in the 90s right? A bunch of orangutans running around wearing clothes, sunglasses, and  drinking fake orange juice? I think some unclever guy in their advertising department was trying to think of a name for a new orange drink, and thought "Orange? ORANGEutangs? I got i! TANG!" Uh. No, buddy. There's no G in there. Now nobody knows how to say orangutan. Thanks Tang.

Actually word ‘orangutan’ comes from the Indonesian/Malay words “orang” (person) and “hutan” (forest). So 
orangutan means “person of the forest”. Note that this is why we call the orangutans at Cabang Panti OHs.  So even before the theory of evolution was introduced, or before Alfred Russell 
Wallace came to the Malay archipelago and provided the first full description of orangutans to science, the native Indonesian/Malay people recognized the great similarity in appearance between orangutans and people. Today, we know why we’re so similar: Both humans and 
orangutans are apes, and we share a common ancestor and 97% of our DNA with them.  A word on apes: don’t call them monkeys, unless you want every primatologist within a 15-mile radius 
to track you down and give you a rant about the differences between apes and monkeys. Simply put, apes are a group of primates with upright postures, stiff lower backs, and (most importantly) 
big brains for their body size. If you want a quick and dirty way to distinguish apes from monkeys, well monkeys have tails and apes don’t. Other apes include chimpanzees, bonobos, gorillas, gibbons, and (of course) humans (no disrespect to gibbons, which are classified as lesser apes rather than great apes, because they’re smaller and more distantly related). 

There’s two species of Orangutans: The Sumatran Orangutan (Pongo abelii) and the Bornean Orangutan (Pongo pygmaeus). The bornean species is further divided into several subspecies, 
depending on where the population is found on the island. The orangutans at Gunung Palung are classified as Pongo pygmaeus wurmbii, and these are found in most of central Kalimantan as 
well. The Sumatran Orangutan is found only in Sumatra (I know, plot twist!). While both species of orangutans are endangered, the Sumatrans are listed as critically endangered, because they 
have an incredibly small population. 
There’s a few differences between the two species: Sumatran orangutans are a bit larger in body size, and seem to have a slower life history than Bornean orangutans (e.g., they take longer to 
mature and have offspring less frequently, among other differences). This may be part of the reason that Sumatran orangutans are more endangered, since their life history may make their 
populations slightly more vulnerable to hunting and habitat destruction. The Sumatran species almost rarely comes down to the ground, whereas the Bornean ones do so periodically. There is 
little danger in coming down to the ground for Bornean orangutans, but the ones in Sumatra have a big problem to worry about: the fierce Sumatran tiger! It’s a risk coming down to the ground 
for them, because there might just be a hungry beast waiting for his lunch to climb down the tree – this may account for this behavioral difference among the Bornean and Sumatran orangutans. 

Those are just a few of the differences between both species. But what makes orangutans different from all of the other apes? That’s what I’ll be talking about in the next post.