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3 friends at base of huge tree

By Griëtte “Lady D” van der Heide

I wish I could be writing this “Grove of the Month” while hanging upside down in a tree somewhere in Georgia, with my feet on a branch, where my friend Will Cottrell seems to be 24/7. Instead, this story is coming to you from West Harlem, where I am temporarily staying while teaching and doing lab work at Hunter College. As these words hit the paper, I feel immensely fortunate that I was introduced to tree climbing. At the same time, my brain cannot seem to comprehend that so many kids these days are deprived of such outdoor adventures.

View of Kibale National Park from a fruiting Ficus natalensis standing tall in the swamp.

Before heading to NYC, as a Dutch transplant living in hot, shrubby Texas, at the University of Texas in San Antonio, I started to miss my previous indoor and outdoor rock climbing adventures. This, combined with my tendency to hang around primates, led me to my first tree climbing adventure in 2013 at the Institute of Tropical Ecology and Conservation, in Panama. With some help from my academic advisor Dr. Joanna Lambert, Joe Maher as instructor, and two amazing graduate students as climbing buddies, I was all set for a month long rollercoaster ride-like tropical tree climbing course. Joe definitely has special hawk-like skills, spotting mistakes in my climbing hitch from tree crowns away. Jodie Rosam, beyond the ability to descend superfast whenever necessary, has special skills climbing with webbing in small trees. And Adam Clause spots, catches, and releases arboreal lizards in emergent figs before anyone else has a chance to catch their breath from the climb up. Without Joe’s brother Bill, I would not have been able to experience climbing on “stomach loads of grit” in the beautiful forests of Georgia. All these guys helped me tremendously and have been wonderful hosts and friends.

I have recently started to apply tree climbing techniques to my own doctoral dissertation research. I am interested in primates of all sorts; lemurs, monkeys, apes, nocturnal, diurnal, in zoos, and in the wild. Of all primates, I am most interested in arboreal, fruit-eating species. I adore Neotropical forests and their inhabitants, especially the subtropical forests in the Argentinean Chaco where I worked as a research assistant, for Dr. Eduardo Fernandez-Duque, with owl monkeys. These monogamous, territorial creatures roam the forest in small social groups, mostly during the dark hours of the day. High above the ground, they climb beautiful trees, using branches and lianas as hiding places, paths, and food sources. It was in Argentina, that I realized that the key to understanding arboreal primates means joining them in their canopy habitats. 

At Kibale National Park, in Uganda, I have started focusing my research on two monkey species: the grey-cheeked mangabey, and the red-tail guenon. I focus on fruit odors and how monkeys use smell to figure out if fruits are edible. Many primates have outstanding color and stereoscopic vision; thus the sense of smell has been deemed less important in the daily lives of primates. However, being a proper primate myself, I test my food by smelling, touching, and visually inspecting it, even before checking the “use before” stamp that other humans have conveniently added to my processed foods. Other primates must be using multiple sensory cues as well, but how and when do they use odor?

I probably climbed “a fig a day” during my three month stay in the high-altitude tropical forests of Kibale. Some fig species have fruits growing directly from the main trunk and branches. These figs have been challenging to climb, since the short white rope that I use to transfer got stuck behind these fist-sized fruits all the time. I gave up on those fig trees. They won the fight in 2014, but they will be challenged once more, when I return to Kibale. Chimpanzee researchers Dr. Martin Muller, Dr. Sherry Nelson, and graduate student Marian Hamilton, were not only great climbing friends at Kibale, but also a great resource. They “introduced” me to the best fig species of the forest (Ficus capensis), and… by accident, to life in the trees with chimpanzees. Although I had asked another primatologist what to do, ethically and wisely, when chimps happen to enter the tree you are climbing, I was not prepared for the long, silent, wait during the heat of the day. Since I was not in Kibale to disturb the monkeys and apes in their arboreal homes, I stayed in the fig for 3-4 hours, quietly, and slowly changing position occasionally, until – finally – the last chimpanzee left the tree and I descended with fruits and leaves as trophies. Back on the ground, I inhaled a liter of water and some chapattis. 

3 friends at base of huge tree

Griëte van der Heide, Jodie Rosam, and Adam Clause before climbing a giant tropical oak in Boquete, Panama. Picture by Joe Maher.

As part of my research, I collect fruits from the canopy to analyze olfactory cues. Obtaining the fruits from the tree crowns has been a major challenge. Once I am in a good position in a tree, I normally ask one of my Ugandan field assistants, Bruce and Sylevaster, to connect two or three 6-ft poles to a pruner head. I then haul up this system and try to let the heavy pruning head “fall” on some fruit-carrying terminal branches. It has become clear that I was not born to be an arborist. Respect for arborists though; pruning equipment is heavy! After collecting the cut fruits, and safely descending the pruner and myself, I carry the fruits back to camp. At night, I weigh, measure, and photograph them, after collecting the odors emitted from the fruits with a vacuum-pump. I then dry the fruits to analyze for nutritional content and toxins. We also watch monkeys feeding from figs and observe how they inspect fruits. 

I taught Bruce and Sylevaster some basic tree climbing facts. During my last week at Kibale, Bruce and I tried to rig this humongous Ficus natalensis. Even a sidewinder with extra extension (!) could barely get a weight bag over the nearest branch. Of course the weight bag got really, really stuck. We tried every trick I could think of, but only time made this fig forgive its potential intruders. Several days later, when he checked the tree for foraging monkeys, Bruce was finally able to release the bag from its airborne trap. Although Bruce and Sylevaster never climbed a tree, I am hoping that this year I can train to become a Facilitator and take several Ugandans up in a tree.

But let’s not fool myself. I also want to facilitate climbs for selfish reasons. Hanging out in trees with some buddies is much more fun than experiencing tropical tree canopies by myself!!