The Rainforest: a place full of amazing.

Why is rainforest biodiversity so special, and why do so many plants and animals call it their home?

In the last two years, I’ve had the privilege of visiting two of the great tropical rainforests of the world: the Ecuadorian Amazon, and the Bornean rainforest. I consider it a privilege, because the majority of people in the world never set foot inside of a rainforest. 50% of the world population live in cities, and that number is projected to jump to 70% during the next 35 years. The tropical rainforest is just about the last place the average human would want to venture into, and it’s not that hard to see why. It’s almost impossible to live in it.

Somewhere hidden between all those leaves and branches are countless species of insects, and other animals, invisible to our eyes. 

When western explorers first ran into the rainforests of the Amazon, Africa, and Southeast Asia, and saw the immensely dense growth and all of the gigantic trees, they concluded that the soils there must be the most fertile on earth. Counter to intuition however, the soils there are some of the most nutrient poor on earth. This is because nutrient cycling is incredibly fast in the rainforest, and any nutrients that make it into the soil are immediately absorbed by the roots of all the plants and taken up into the canopy. In fact, 99% of the nutrients of the rainforest is found in the vegetation itself, and not the soils. So any crops one tries to plant in the rainforest will surely fail.

Other than the puny human (try to spot the climber up there!), within those trees are a whole lot of nutrients. 

If that wasn't enough of a deterrent to any would-be residents of the rainforest, the rainforest is also an incredibly dense and arguably one of the most difficult to navigate environments in the world. There are few landmarks, and the trees are so high and the vegetation so dense that one can’t see more than 50m into the distance. It’s no coincidence that the word “jungle,” which is of sanskrit origin, means wasteland.  Without sufficient training, equipment, and supplies, a trip alone into the rainforest would end in disaster for the average person. Our primate ancestors called the rainforest their home, but ever since humans evolved their way into the savannas of Africa, few have ventured back into their ancestral home. We just can’t live in it.

Funnily enough though, in the grand scheme of things, humans seem to be the great outlier in terms of where we live. Covering less than 2% of the earth’s surface, the rainforest nevertheless contains more than 50% of the world’s species of plants and animals. More and more are discovered every day. And not just small things like insects (like the plant hopper!) or plants (like this crazy Chilean chameleon vine – technically not in the rainforest but too cool to not share). Mammals have been discovered as well, as shown by the recent discoveries of the Olinguito in the Amazon, and the venomous Slow Loris in Borneo (the only known venomous primate in the world!). Considering all of the life that’s out there, it’s crazy to think that many scientists estimate that only one fifth of the world’s species have been described. Even how the rainforest became so biodiverse is kind of a mystery, and there’s a multitude of theories proposed to explain it. One of the reasons given is that the environment is so heterogeneous and complex (to begin with, there is a vertical element not seen in other environments to the extent as it’s seen in the rainforest, which has trees 200+ft) that there are thousands of potential niches for different animals to occupy, and speciate.

The golden-mantled tree kangaroo, recently discovered in the Foja mountains of Indonesia. I didn't even know there were kangaroos on this side of Wallace's line!

So with all of this biodiversity in the rainforest, you might think that if you walk into the rainforest, you’ll be running into all sorts of animals left and right. The truth is not quite that however. With all those impressive biodiversity facts and species numbers I always heard about, the first time I visited the Amazon rainforest in the fall of 2012, I was expecting to run into all sorts of crazy animals the minute I walked out. So you can imagine my surprise when I found the rainforest to appear overwhelmingly uniform. And to the untrained eye, that’s exactly what it looks like: one big pile of green. Broccoli broccoli broccoli, everywhere. Out in the open, there are no animals in sight or anything besides bunches of of branches, vines, and leaves. You might spend a few days in the rainforest, and then leave thinking “alright, I think I saw all there is to see.” But in actuality, that couldn't be farther from the truth.

To get the most out of the rainforest, and experience the biodiversity that it has to offer, it takes a lot of patience, and a very observant eye. You know for a fact that everything is out there because your ears don’t lie. You can hear the call of the wild every morning and every night, when multitudes of species in the rainforest – cicadas, gibbons, birds, etc. – call out and resonate throughout the rainforest. But everything, absolutely everything is hiding. Under leaves, blending into the cracks of tree trunks, high up in the canopy, almost every form of life out there blends into its surroundings, and appears invisible to those who don’t know where to look. But it The longer you spend in the rainforest, the better you’ll be at spotting everything. It’s not ‘til then that you realize you could spend every hour of every day walking around in the rainforest, and not see everything. Even the big things! I have spent almost a year now living at Gunung Palung National Park in Borneo, and I’ve yet to see any sun bears, leopards, pythons, or lemurs. But they are out there, and I’m still holding out hope that I’ll at least get to see a bear before I leave!

If I act like a sun-bear, maybe all the sun-bears will come out too.

It takes a bit of luck to see cool things out here, some of which I’ve had during my time at Gunung Palung. I’ve definitely seen over 15 orangutan matings now (so many that I’ve lost count!), which tend to be pretty rare events to see, much less capture on film (which I also have!). I’ve also seen two male orangutans go at it head to head on the ground, extremely rare events to witness. My most notable sighting, and the source of a bit of jealousy at camp, was when a Binturong (AKA, a bearcat!) ran up to me as I was sitting somewhere up in the mountain; I heard a noise coming down hill, and prepped my camera, unknowing of what exactly was coming down but ready to get it on film. I got really excited when I saw what it was, but it passed by me so quickly that I could only capture a moving blur on the camera. But the ‘cat’ in the bearcat was a curious creature indeed, and when it spotted me it turned around for a closer look. As it stared at me from a few meters away, I managed to snap this photo, proof of my sighting to everyone at camp!

A Binturong, AKA a Bearcat. I bet there are only a handful of non-camera trap photos in the world taken of these guys in the wild. 

Every time you step into the rainforest, what you see is luck of the draw, a spin of the wheel. But with some patience and a good eye, you can double the odds. The rainforest can definitely be a bit overwhelming, but it is without a doubt an awesome place to explore. 

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.