Like all the other nights, this one also feels like a warm blanket around me. There has been little rain lately, so it’s not clammy. With my big backpack filled with field equipment I walk over the path, carefully holding my two speakers in my hands. The slope is steep, will I get my speakers down in one go? Carefully I balance, and then a small jump. I look back: how I’ll get them back up is a care for later.
I set up my new experiment (read here about my previous one). Speaker on one side, speaker on the other side. In this new experiment we investigate the influence of habitat on the predation preference of bats. Does vegetation affect the echolocation of bats? Aside from that, there is the suspicion that vegetation influences the amount of flies bothering the frogs. The speakers play the sound of the tùngara frogs (listen here), sometimes with vegetation on top of the speakers and other times without. With this experiment, we hope to see an interaction between vegetation and predation risk by bats or parasitic load by the bloodsucking flies. I put the cameras in their place, so they can be the silent witnesses of the visiting bats. The fly traps are ready to catch ignorant flies with their stickiness. Infrared lights, cameras, action!
I walk back through the dark forest. While I walk, small white diamonds shimmer around me. In the understory, on fallen trees or overhanging palm leaves, you see them everywhere. The small diamonds are spider eyes, and we call their glitter ‘spidershine’. So nice to know for an arachnophobe (someone who’s afraid of spiders, ed.) like me. In the past few months I’ve learned to appreciate it: at least you’re never alone in the rain forest.
Not just the eyes of spiders reflect the light of my headlamp. From their eyeshine (tapetum lucidum) you can identify many more animals. Small white eyeshine are as mentioned spiders, but if the eyeshine is small and red, it’s most likely a moth. Big, red and in the water are caimans and crocodiles. Big, white and (almost) imperturbable on the road are nightjars. Big, white and moving through the canopy are kinkajous or olingos: sometimes they curiously look down on you. The eyeshine I haven’t seen yet is green: wild cats like ocelots.
My focus on the reflection of light in the eyes of wildlife illustrates how limited our visual capabilities are in the night. You’ll only see as far as your headlamp reaches, outside your bundle of light it’s pitch-black. Other senses become stronger: sounds are there all the more. Like the tree next to me, which is firing its fruits like bullets. Rattatat. It almost feels like it wants to be set free from this burden as soon as possible, rather today than tomorrow. Cicadas overrule the sounds of other insects. Howler monkeys sound like the rumbling thunder, which sometimes seems to come closer and other times dissipates in the distance. Gladiator frogs drum on the wood of the branches they rest on with their calls. The sound of fluttering wings betrays the presence of bats. The frogs and birds confuse me as a Dutch person: some frogs sound like Dutch birds and I would identify some bird sounds more as frogs. Last but not least, the rain forest wouldn’t sound like the rain forest without the sound of drops on the big diversity of leaves. For more sounds of the rain forest, listen here to recordings made by Peter Marting.
Circle of life
Aside from all these sounds there is one smell which is incredibly distinct for the rain forest: the smell of rotting fruit. The smell is almost a symbol of the fleetingness of this place. An abundance of nutrients for an abundance of species. Birds, monkeys or bats eat ripe fruits and play an important part in dispersing seeds (and some species in pollinating plants). What remains, is too much or is overlooked by other species, is food for wasps or ants. Fallen leaves are converted in nutrients for the soil, which helps other plants grow again. Dead animals are skillfully dissected and are food for maggots. The reason why researchers here at STRI are performing research in the tropics for more than 80 years now, is the huge complexity and diversity. In the tropical rain forest many more species are involved in the circle of life than in other ecosystems, like our Dutch nature. All the above mentioned parts maintain the circle: the end of one element stimulates the start of a new one.