Rio Maria and the jungle

Our research group had a central goal of finding out what would happen to the high elevation jungle streams after the tadpoles disappeared, so it was necessary to measure everything we could about the biology of the streams while the frogs and tadpoles were still there. Part of the process of scientific understanding is detailed observation, and we needed to be sharp and pick out the most important details to measure in this stream, to capture the true way the system worked. The baseline conditions of how the organisms influenced their environment, which organisms were there, and how they interacted all needed to be measured. We had limited time on this trip and had to make the best use of that time. This is the scientific way to talk about the environment we were about to enter, but there is more to biology than just measuring things.

It was hot in the sun out with the trucks as we fussed around with our gear. We got all the stuff we needed for our first set of measurements and started loaded up for our first trip into the jungle. The edges of the road were overgrown with a tangle of grass and bushes, as is always the case in the tropics; a road cut lets in valuable light and the plants fight for a toehold in this newly opened habitat. We needed to force our way through this on a tiny trail that had been hacked out by machete a few days before, and there were holes, fallen logs, and slippery muddy bits that needed to be negotiated with heavy loads of equipment. Our gum-boots did not making the footing easier, but they probably would protect from the fangs of a snake, and did keep our feet dry. Of course, we needed to also keep an eye out for sunning fer-de-lance, the extremely toxic snake that frequented the area.

As I entered the damp shade of the dense jungle near the stream, the temperature became more pleasant. This was another world. Rio Maria was a beautiful stream as it flowed through the jungle. A few shafts of sunlight found their way through the riot of tangled green to dance on the surface of the stream and dapple the rocks at the bottom of the clear waters.

Clear-winged butterflies flitted through the forest. These butterflies are fantastic as they have a rim of color around one or two almost completely clear wings. The oval-winged butterflies appear to fly slowly, but prior experience with a butterfly net convinced me that the clear wings make it difficult to see them and judge what direction they are going to fly. Or maybe I just suck at catching flying insects. Clear wings are probably a good predator defense, at least against inexperienced collectors.

Garish red flowers (hibiscus, passion flowers) dangled from overhanging vines or grew from the jungle floor. The vegetation is not extremely dense at the forest floor because so little light reaches it. Mosses covered most surfaces, including the tree trunks, fallen logs, older leaves, and the edges of the rocks near the streams. Tropical rainforest is part of what lured me back to Central America, and reality exceeded memory.
There were frog calls from hundreds of feet above in the tree canopy, down in the low vegetation, near the stream, and from the hillsides that surrounded us. The sound of chirping frogs constantly came from all directions. The calls blended with the insect sounds (cicadas and others) and bird calls.

Our first task was to decide which section of the stream would serve as the research site, so we set off through the jungle upstream to have a look. With each step in the forest, small brown frogs jumped out from under our feet. We had to be careful not to step on them. At the stream crossing (chosen with care so as to not disturb the bottom of the stream for our experiment) the pool had hundreds of small tadpoles swarming along the bottom.

I have spent quite a bit of time studying aquatic systems and the only time I have ever seen so many frogs and tadpoles at these densities was in the quaking bogs surrounding small lakes high in the Oregon Cascades in the 1980’s. These bogs form at the upstream end of lakes and have floating vegetation mats and deep water holes that the unwary will fall into. The conditions, once the snow melts, are perfect for breeding frogs, and they are everywhere there. My mind drifted back to Oregon, and then snapped into focus on the jungle frogs at hand.

Water in the stream gurgled between the rocks, rocks rounded by the many floods over the centuries rolling them along the stream channel and grinding them to smoothness. First they were eroded by the weather until were free from the volcanic hillsides above, then they fell and washed down the outer slopes of the crater, and eventually they would be ground by the energy of the water scraping them against other rocks to end up as grains of sand on the ocean beaches tens of miles away.

Occasionally parrots would make a racket in the distance, a toucan would fly high overhead, or a blue butterfly with a wingspread wider than my head (Morpho) would glide past. I found myself looking for monkeys and sloths, but found none.