Steve Yanoviak, tropical biologist
Tuesday, 29 Aug 2000
MONTEVERDE, Costa Rica
I looked in the mirror this morning and found seven very itchy kissing-bug welts on my left shoulder. I only recall three bites, so I guess you could say the bug has the adaptive advantage.
It rained throughout last night with plenty of thunder and lightning. I get a real kick out of thunder and lightning — if it is going to rain like hell, it might as well be interesting! This morning was absolutely beautiful, so I went up the tree I rigged yesterday. Before I tell you about what I experienced up there, I want to talk a little about the equipment I use to climb trees and about the biology of this particular tree. (If it is not already apparent, you can count on some kind of lesson every day — I love biology, and I love to teach.)
The equipment I use to climb up the ropes is pretty basic. I wear a standard rock-climbing harness that is outfitted with a variety of carabiners and slings made of tubular webbing. The webbing and ‘biners enable me to safely climb around on branches, away from the rope. I use a pair of ascenders (also called “Jumars,” which is a brand name) to go up the rope. Each ascender is just a metal handle with a toothed cam inside. The ascender will go up the rope without resistance, but the teeth of the cam grab the rope when downward force is applied. So, it is basically a unidirectional system that allows a person to move along or up a rope without fear of sliding down. I have one ascender tied to my harness, and the other has two loops of webbing for my feet. To go up, I lift my feet and use my hands to slide the foot ascender up the rope. Then I stand up in the foot slings while sliding the other ascender up the rope. I lift my feet again, stand up again, and so on. Just imagine a human inchworm.
Climbing 30 meters up a rope is not as difficult as it sounds. After some practice, it takes about the same effort as climbing 10 flights of stairs. I have taught all sizes of people to do it. Most try too hard at first, and it typically takes them about 30 minutes to go up 30 meters. After some experience (and after the fear subsides), most people can do the same in less than 10 minutes.
The tree I climbed today is a strangler fig (Ficus sp.). Many people in the U.S. have smaller versions of this tree growing in their homes. I talked a little about epiphytes in my first diary entry. True epiphytes live on top of other plants without a connection to the ground. Strangler figs are called hemi-epiphytes because they start out as small trees growing on top of other trees, but eventually send roots down from the canopy and establish a connection with the ground.
Strangler figs get started when a bat or a bird eats a fig fruit and deposits the seeds in the crown of another tree. The fig sapling grows into a small tree within the crown of the host tree, and its roots grow down the host’s trunk, eventually enveloping the host tree completely. Hence the name “strangler” fig. After may years, the host tree dies and begins to rot, leaving the large hollow fig tree behind. The jury is still out on what causes the host tree to die — it is either literally strangled by the fig, or the dense fig foliage in the crown out-competes the host tree for sunlight. It is probably a combination of the two.
The trunks (old root systems) of figs are convoluted and easy to free climb. The local kids have many favorite hollow fig trees that they climb from within, greatly impressing the tourists when they poke their heads out of the top of the tree trunk.
I have climbed more than 200 tropical trees, most of them more than once, for a total of well over 1,000 separate ascents. No two climbs have ever been the same, and I can safely say that I have seen something new each time. Today it was a big (3-4 cm length) long-horned beetle that flew into the crown of the tree shortly after I arrived. I had just secured myself to a branch and unclipped from the rope when I heard the buzzing of a large flying insect headed my direction. There was a big “thwap!” as it landed ungracefully on a leaf about a meter away. I grabbed it so I could photograph it for you. As soon as I picked it up, it started making a high-pitched buzzing sound, which is probably pretty effective at deterring birds and other predators — not to mention that it has big mandibles that can easily cut through skin!
The branches of this tree are completely covered in epiphytes — lots of orchids, ferns, and bromeliads. It also has several woody epiphytes, most of which are related to blueberry bushes. I sat there almost motionless for at least a half hour watching the hummingbirds and bananaquits forage among the epiphyte flowers. There was only a light breeze blowing today, so things were pretty quiet in the tree. In the distance I could hear the howling of howler monkeys and the occasional call of a pair of prong-billed barbets. I saw a group of odd-looking flies hovering among the branches. I’m just guessing, but I think they were males of the same species in competition for the best patch of space to attract females. A fly would hover for several seconds before being attacked by a second fly. An air battle immediately followed, and it reminded me a lot of jousting — each attacker trying to knock the resident fly out of that particular patch of air space. I think I could have watched this go on for hours, but clouds were building on the horizon and I had other things to tend to …
My purpose in climbing today was to look around for spiders. I have an assistant coming down here soon who will be doing a project related to canopy spider diversity, and I wanted to start thinking about the logistics of such a project before she arrives. Spiders are abundant in the canopy, and are perhaps the most important predators of caterpillars and other insects that hang out in vegetation.
Today, like other days when I’ve searched for spiders, I found surprisingly few. Most spiders are active at night, and I’m pretty certain that we will have to do some night climbing in order to get enough data for the project. I’ve done a few night climbs before, and I can tell you that being in a tree at night is a completely different experience from day climbing. For one thing, you can only see as far as your light. This means that the ground is never in view, and it is very easy to forget how high up you are. Also, there is a completely different fauna active in the canopy at night. A sort of changing of the guard occurs as diurnal animals go into hiding and nocturnal animals come out to feed. I will not be doing any night climbing this week — perhaps in a future Grist diary.
Tomorrow I will be working on the ground in the forest. I’m sure I’ll have plenty to share with you afterward.
It is pouring rain outside again, with plenty of thunder and lightning. A fresh batch of gallo pinto awaits me …