Blog Post

Lessons learned in tropical tree climbing

"Oh yeah, I forgot about that..."

The beginning of any field study includes at least a few remedial lessons. For weeks before I start climbing, I wake up in the middle of the night in a panic that I have forgotten all my knots. I look over old gear lists trying to figure out what I’ve brought with me in the past, and whether I really need all those karabiners, batteries, and feet of rope. I worry that I will not be quite as adept with the 8-foot-tall slingshot I use to help me get my rope into the tree.

All of this of course could be solved with a bit more disciplined climbing practice between field seasons, but somehow that always seems to drop down my priority list when there are new datasets to analyze, grants to apply for, papers to write, and the many other desk-bound tasks required of a scientist. As such, I have to accept the fact that some of my equipment leaves me scratching my head until I take the time to think it through and test it out.

Inevitably once I get started, I realize that after hundreds hours of practice the knots are fortunately locked in my muscle memory, the seemingly extra equipment all gets used and is thus worth the extra baggage fees, and my slingshot game is actually still pretty strong.

The Rainforest Discovery Center (RDC) is operated by the Sabah Forestry Department. RDC is adjacent to the Sepilok Forest Reserve outside the city of Sandakan.

I recently arrived at my first research site at the Sepilok Forest Reserve located in the eastern part of Sabah, one of the two Malaysian states in Borneo. I am based at the Rainforest Discovery Centre (RDC), an environmental education center run by the Sabah Forestry Department.

After a long hiatus from intensive climbing, RDC provides a perfect setting to get back into the swing of things with my fieldwork: highly kept (and sometimes paved) trails to help me get into the forest, a canopy walkway that gives me an 11-meter head start up the some of the largest trees in the park, and a refreshment stand right at the exit where I can grab an ice cream at the end of the day (which I need or else I’ll die). Conditions won’t always be this posh, but I’ll enjoy the amenities while I’m here.

The Canopy Walkway at RDC is 347 meters long with two towers that extend 25m above the forest floor. Visitors can walk through the treetops to observe canopy flora and fauna...and also helped me cheat my way into some of the tallest trees in the park.

On my first day searching for trees, there was a nearby fig tree that was producing ‘fruit’ at the time (figs are actually a modified flower, not a true fruit), so I decided to take advantage of the opportunity.

Figs are an important food source for many animals, and a fruiting fig tree acts like an aromatic dinner bell. The branches teem with life as the smell of ripe figs attracts bats, monkeys, birds and other frugivorous (fruit-eating) wildlife to the tree. In exploratory surveys, it can be extremely helpful to document activity at attractive sites like fruiting trees, mineral deposits (salt licks), or in dryer climates, watering holes.

As I set up my rope, my mind was focused on the images I was sure to capture: a squirrel scampering down the branch on its way to a feast, a macaque with a ‘chubby bunny’-style face full of figs ambling past the camera. Internet memes had taught me to hope for images of a monkey (or in this case, a chimp) walking upright, dropping figs as he tried desperately to gather them in his arms. That, of course, is ridiculous, at least up in the trees. But for the record, if you’ve never seen a primate scampering on two feet, its little legs whirring under an uneasily balanced body, you have simply never witnessed true humor.

What I did not have in mind was the other frequent visitor to a fresh crop of figs.

Predatory ants can help defend fig trees from parasitic insects. In the process they can also discourage larger animals (like me) from spending time in the tree.

Fig (Ficus) trees are quite famous for their relationships with insects, namely the wasps that pollinate them. Ficus trees emit a unique chemical into the air to signal to its specific wasp pollinator that the figs are ready to receive pollen. The wasp arrives, crawls through the hole in the base of the fig and simultaneously pollinates the fig while depositing its eggs. A great deal of attention has been placed on this mutualistic relationship (in which both parties stand to gain something from the other), but Ficus trees can also benefit from the activity of another six-legged inhabitant – ants.

There are many different types of ants that can be found on Ficus trees. Some are there to feast on the figs themselves like all the other animals. However, there are also predatory ants that hunt the other insects that are drawn to the sugary bounty in the tree. In the process, they fend off insects, lizards, and sometimes me-sized animals as well.

Most ants tend to be fairly indiscriminate about what they devour, perfectly happy to hunt the pollinator wasp along with any other prey that may show up. However, pollinator wasps are quite efficient at entering their target fig, which allows them to escape the hungry ants. Some pollinator wasps can even ‘mask’ themselves with scents that mimic the chemicals of the figs.

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In addition to the pollinator wasps there are non-pollinating wasp species that show up trying to lay their eggs inside the same figs as the pollinators. Because they offer no benefit to the tree, these wasps are actually parasites that prevent the figs from maturing. Presence of predatory ants on Ficus trees can keep parasitic wasps numbers low. So even though the ants may devour the occasional beneficial pollinator wasp, overall they provide a net benefit for the tree.

I have a tepid relationship at best with ants. I’ve done a fair bit of complaining about ants in the past, sometimes in writing, but mostly in end-of-day rants to anyone who will listen. That said, I just looked up a bunch of facts about why they are important, so I feel like I have some ant credit now.

In the past I’ve learned to inspect trees beforehand for ants and use caution when I see them crawling up and down the trunk around a nest on a branch. You can minimize contact with them if you avoid stepping on branches and rely on your ropes alone to position you in the tree. But these lessons were completely lost on me as I powered my way into the tree.

By positioning yourself in the tree using only your ropes, you can minimize contact with crawling insects, which also reduces damage to the bark and the free-living plants (epiphytes) that grow on the branches. This technique is sometimes called “climbing on a bridge.” Photos by Sean Mattson

I launched my line into the tree and brushed away the ants that came crawling down to inspect it. I pulled my rope over the branch I was to climb and again ignored the tiny sentinels inspecting the nylon vine that had just entered their territory. I attached my harness to the rope and started to climb, flicking the occasional ant off my ascender and away from my hand. And then I made my biggest mistake yet.

Eyeing the spot where I wanted to set up my camera, I stood up on a branch below and an explosion of crawling legs and biting jaws came rushing onto me. Before I could even think to pull my feet up I was completely covered. I was shocked at how quickly it all happened, but of course the reality is that in this environment they are fast and I am slow – in movement and in thought, apparently. Flailing about, I desperately tried to brush, smash, and pull anywhere I could reach.

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I am neither an entomologist nor did I take the time as they were plunging their mandibles into my skin to count the segments on their antennae or the ridges on their bodies in order to properly identify them (utter laziness, I know). Thus, I have no idea exactly what species these were, but I’d say they were on the less dangerous, though somewhat angry side.

It is worth mentioning, however, that while not in a position to threaten my life, these ants do come with the lovely ability to produce formic acid, which they deliver with their bites. This causes a rather uncomfortable stinging sensation, one that returns hours later when you attempt to rinse off your lacquer of sweat, dirt, and smashed ant parts.

I didn’t manage to take any pictures of the ants as they were actually biting me, but I made a Instagram story (@mclean_ka) to express my feelings about the ones I’ve gotten to know so far.

I briefly considered staying in the tree to set up my cameras – to endure the pain in the name of science. My tolerance for pain, however, is far from impressive, particularly when it can be avoided. The few times in life I’ve considered getting a tattoo have been quickly dismissed when I begin to consider the needle. I’m not afraid of needles per se, but what’s the point if it’s not going to protect you from disease? Might give you one, actually. When they invent a way to get a tattoo that feels like it’s being licked on by kittens, maybe I’ll reconsider.

Giving up on the climb, I made a rapid albeit uncomfortable descent to the ground and did a painful little dance to rid myself of the remaining attackers. Feeling the defeat of a failed day in the field, I returned home only to realize that I had forgotten a key piece of the camera mount, which would have prevented me from setting up the camera even if I had decided to brave the swarm.

With the bites still tingling on my most-of-me, I returned the next day with a more careful climbing strategy and all the necessary equipment. After successfully deploying two cameras without incident I tried to avoid thinking about the very real possibility that the animals I hoped to document might also be deterred from the tree just as I had been. With that, I pressed on. As I write this all 23 cameras I brought to Malaysia are running, and I will be making my first collection soon.

Ant attacks following my own ignorance are perhaps just part of this year’s climbing bootcamp. And hey, at least they weren’t bees.

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