Sights and Sounds from the Tree Canopy

It was June 2008, and a former colleague asked if I wanted to work in the Kalakad Mundanthurai Tiger Reserve. I was just out of college and aspired for a career in ecological research. I remember saying yes, without a moment’s hesitation, and only later asking what the project was about. It was an opportunity to work with the first canopy biologist in India and study epiphytes — plants that grow on other plants — in the tall forest canopy of the southern Western Ghats.

Growing up in the city, I had little exposure to climbing trees and the thought of being up in the tall forest trees made me wonder if I made the wrong choice. A few months later, I was in the wet, evergreen forests of the Kalakad Mundanthurai Tiger Reserve (KMTR) in south Tamil Nadu, looking up at a Cullenia exarillata tree, which I was told, was a window to what is called the last frontier in biological research — the forest canopy.

Humans tend to look up to the sky both for practical purposes such as to check on the weather, and for existential purposes, such as to ponder if there is a heaven or hell up there. Perhaps it is with this same notion that we began to look up at the tall, often unbroken, chain of forest crowns where life appears to thrive. The forest canopy has always been a mystery to us earthbound bipeds. Over time, we have tried to explore canopies in many ways, and our understanding of them has now advanced. One of the easy ways in which canopies were once studied was to simply cut down the tree and look at what was in the crown, but that is, needless to say, destructive. The other method was to send monkeys trained to collect leaves, fruits, and even orchids. There is a limit to how much can be done with such tools. Thus, canopies remained a mysterious place on Earth until the 70s when researchers began to use rock climbing equipment to get into the canopy. This method was called the single rope technique, where a fishing line is shot over a branch using a powerful catapult and a climbing rope is hauled up. One end of the rope is tied and the other end is used to climb up using a pair of ascenders, which are devices that move only in one direction on the rope, and the person climbing goes up like a worm, sitting and standing attached to a harness.

Up in the tree, I was suspended on a rope in a three-dimensional space, with life all around me. Reaching the safety of a branch, I made myself comfortable and slowly began to look around. The tree was laden with epiphytes of several species. The constant drone of cicadas was interrupted occasionally by a flock of black bulbuls flying from an Elaeocarpus munronii tree. With a gentle breeze shaking the leaves, it felt surreal. Soon, it was time to descend and that was both scary and relatively easy. I had to push myself off the branch and use a friction controlled device to regulate the speed of the descent. I spent the subsequent two years going up and down trees in search of epiphytes.

Epiphytes are a fascinating group of plants with several adaptations to survive the harsh environments of the canopy. Their ability to grow without soil has been a fascinating aspect of their biology. Most epiphytes depend on what is called “canopy soil organic matter”, which is the debris of leaf litter, bark, and fruit — decayed among the nooks and crannies of branches. Here is where epiphytes typically tend to grow. Epiphytic plants such as the mistletoes are parasitic when they start, sucking all the nutrition they need from the host plant until they put out their leaves and become independent. Members of the mistletoe family also recruit two other birds for their survival: a species of sunbird to pinch the flower open and pollinate it; and a flowerpecker to disperse the seeds. The flowerpecker consumes the fruit as a whole and passes the seed. The seed is coated with a sticky pulp and the poor bird has to literally rub its bottom on a tree to get the seed off. Other epiphytes such as orchids are rather harmless to the host and only use it as a substrate to grow. Orchids have specialised roots called ‘haustoria’, through which they absorb nutrients and moisture.

One day, while in the canopy, I was lucky to encounter a troupe of the endangered lion-tailed macaques. They were not particularly shy and were watching my assistant Chian and me climb up a tree. All the while, we could hear their soft, cooing communication calls. Once we reached the top, the alpha male appeared a little startled and began to challenge us by shaking the branch vigorously. We looked away and did not make eye contact, and soon, he lost interest and moved away. Another day, we climbed up a tree and encountered a green-bodied large-scaled pit viper, which is found only south of the Palghat Gap in the Western Ghats. This snake was perched among branches at around 32 m above ground. We did not have to think too hard about why the snake was up there — there were plenty of frogs up among the leaves.

At night, the forest canopy turned into an orchestra of sounds. We climbed up the tree late one evening and spent the night curled up in the canopy, just like monkeys. Through the night, we shone our torches towards the sounds of frogs. Within a few hours, we spotted a frog that was not known to science. A year later, we described the frog as the Kakachi bush frog (Raorchestes kakachi) after the place where we first saw it. This later led to a research project to monitor frogs in the canopy over longer periods.

The canopy may be the last biological frontier, but it is the first layer that intercepts the atmosphere. Here, the climate is extreme, with harsh rainfall, wind, and relentless sunshine. It is a difficult place to survive. With the effects of climate change, canopies are the first layer to take the hit. It is imperative to at least document what is up in the canopies, let alone observe and document what is happening to them over time. If we don’t start paying attention now, canopies will fade away as a mysterious thing of the past, of which we know nothing.