July 31, 2019 by anon
My first day in La Selva and here we were, just having finished lunch. Still new to everyone and everything, I’d found the rice and beans delicious and my joy on discovering fresh local fruit at the salad bar was unbounded. The shower and the meal had revived me sufficiently that I could ignore my lack of sleep. Now I was eager, impatient, for Hilda to take me to the forest and show me where we were going to work.
The work itself was to be focused on the foraging behaviour of a single species of bat: Glossophaga commissarisi, a Neotropical species native to Central and South America. They were a little smaller than a typical house mouse, but several times cuter in my very unbiased opinion. It mystified me that anybody anywhere could find bats ugly, and that was especially true of this species. They had sweet little teddy-bear faces and a leaf-shaped nose typical of their family (which also included the true vampire bats), involved in directing their echolocating calls. G. commissarisi was commonly known as Commissaris’s long-tongued bat for a good reason: they used their ridiculously long tongues to probe flowers for nectar, their main food. They were the hummingbirds of the mammal world, hovering animals with a metabolism so insanely high, they could eat 150% of their body mass in a single night.
It was my little joke that our beloved bats were on a permanent sugar high, and that’s why catching them took some practice. When we had them in captivity in a flight cage it usually involved chasing them around with a butterfly net and that was relatively easy. Catching bats from the wild, on the other hand, was a different story altogether. As I’d soon find out.
The idea was simple: we would catch bats and put a small group of them into a ‘flight-cage’, a small cabin in the middle of the forest where we would set up a system to record their behaviour. Then we’d release them back into the wild, after their few pampered days in our experiment. All the bats had to do was play with small electronic devices that logged every one of their visits and rewarded them with small drops of sugar water (their “nectar”). We called those devices ‘flowers’, because that’s what they were as far as the bats were concerned. For a human, however, it was difficult to imagine an uglier blossom – all plastic and wires on a metal support rod. The head of the flower was circular, where the bat could stick in its little leaf-nose to pick up its sweet reward. We would catch the bats soon enough, but our task for the day was to check the equipment and calibrate it so we were sure the drops of sugar water were of the right volume.
Hilda led me to the office first. She pulled out her field backpack and began throwing things into it. A notebook and pencil, a syringe, an Eppendorf tube, miscellaneous tools, a spare headlamp and batteries.
“Take your headlamp,” she advised, “It’s dark inside the flight cage.”
“But it’s broad daylight!”
“Trust me, you’re going to need it.”
She pulled on what looked like a man’s button-down shirt and strapped on her head-lamp. I snapped on my own and pulled on a thin but full-sleeved jacket – I didn’t need anybody to tell me that exposed flesh in the forest was a bad idea. Boots were slipped on and Hilda led the way behind the office and past the entrance to the laboratories, where a washing line hung low with dripping white sample bags and a row of bicycles were suspended from a rack by their front wheels. Just behind the building, the forest suddenly began. No gradual thickening of trees or grass getting higher – you were simply plunged into the understorey.
As we crossed a tiny wooden plank, the precarious bridge into this magic kingdom, I could just discern a foot-path into the trees made of square tiles covered in moss. The advantage of this over a dirt-path was clear: the tiles wouldn’t disappear into the mud when it rained.
“How far is the flight-cage?” I asked.
“There’s three flight-cages, and it’s not far, it’s just ten minutes we have to walk.”
“Awww.” My hopes of heroically long treks in the jungle every morning vanished.
Ants swarmed over the ground. Daddy Long-legs were visible on every tree. Vines smacked you across the face when you least expected it. The mosquitoes whined eagerly in your ear. If this wasn’t the real forest, I didn’t know what was. I took deep gulps of the warm, misty air and filled my lungs with a thousand earthy fragrances.
We had been walking a couple of minutes when Hilda pointed to the left.
“That’s one of the flight-cages. We have three, and that one is destroyed. A tree fell on it.”
“No, it did, it was a bad storm. A lot of people have their equipment set up in this part of the forest and it all got destroyed.” She hopped off the path, walked to the door of the broken cage and pushed it open.
The cage was the size of a small room, high enough to walk in without bending and three feet to spare. There was a thick carpet of dried leaves on the floor and a gaping hole in the roof through which sunlight streamed in. There wasn’t an actual tree trunk lying in the cage but branches hung through the gap in the roof. The frame of the cage was wooden but rotted through. I couldn’t imagine doing any more experiments in here. Even repair was out of the question; the cage simply had to be built again. It wasn’t just the fallen tree; to me, it seemed the whole thing had been literally devoured by the forest.
We walked a little further and two large shapes loomed up directly ahead. These were the flight-cages we were working with, and in remarkably good condition by comparison. They had sloped roofs made of large sheets of iron screwed into the framework of the cages. One of the cages had a frame of light but solid-looking metal bars; the other had one of wooden planks nailed together. Mesh was draped over the frames of both cages and tightly secured to create a snug, green cube that the mosquitoes couldn’t penetrate.
“I’ve prepared the flight set-up in this one,” Hilda indicated the metal cage and opened the door. I shot a look over my shoulder at the second cage – it was obvious even at first glance that in many places its wooden frame had been nearly eaten through – and followed Hilda into the metal cage.
I was thrilled. Here were our ugly little flowers, hanging from a light set of plastic poles and spaced in a circle like a maypole around the high table in the centre that held the pump that would push liquid through the system. None of them had the little doors in front of the flower heads I was used to, but they had circular plastic cones around them instead.
“These don’t have any doors! And where is the RFID reader?”
“These are the readers.” Hilda tapped one of the plastic cones. “See they have this little wire here and that’s the antennae. There are no doors though, we never used them here.”
As soon as we introduced a bat into the experiment, we would give it a little necklace – a Radio-Frequency Identity tag that the readers of the flowers could detect. That was essential: it was only when the correct bat was detected at the correct flower that a reward would be triggered. The computer would log the presence of the bat and give the system a signal, a pinch-valve would open, the pump would move, and a drop of sugar water would be pushed out of the flower for the bat to lick up.
“Can the bats even get in there?” I poked one of the flowers doubtfully. “This cone thing seems kinda deep.”
“Yeah, it works good because they have to really stick their noses into the reader close to the antennae to get the nectar.”
She tossed down her backpack, opened it and we started to prepare for the tasks we had to do. The plan was to measure the volume of liquid dispensed by each of the flowers to ensure there wasn’t too much variation around the value we programmed into the system. We played ‘bat’, setting off the readers with a little RFID tag so the flowers produced a little drop of water; we carefully collected the water in the Eppendorf tube, sucked it up with a graduated glass syringe and took the reading. It all struck me as a little on-the-fly, but Hilda anticipated my unasked question.
“You can see we improvise a lot here in the field. This is not a very precise way of doing stuff, but it works. And here, when we find something that works, we stick to it.” She smiled, and the wealth of meaning behind that simple statement struck me. Failed attempts at improvement, updated software that could not interface with the hardware, animals refusing to learn experimental protocols, apparatus that fell apart the first night of training, months of wasted time… These were the occupational hazards of scientific research but here they were compounded by the simple fact that help was far away in both time and space. There were no engineers around to fix a broken part, and if the software didn’t cooperate, it could take days of emailing across time-zones to figure out why. It came home to me all over again as I saw the outdated versions of the software, the slow pumps, the powdery white fungus on some of the equipment, the Pepsi bottles used to collect the waste liquid out of the system, even the mushrooms growing in a corner of the cage.
The weak sunlight coming through into the cage walls had changed to a deep shade of gold with the approaching sunset, and the crickets were just beginning to sing when we were finished. My feet were aching in their new boots and exhaustion had crept over me like a thick fog, blurring my vision and dulling my mind until I couldn’t form coherent sentences. Silently we packed away our equipment and I stumbled back through the forest in Hilda’s wake, no longer caring to swat away the hordes of mosquitoes pursuing us.
I have a dim, hazy memory of three people joining Hilda, Alejandro and myself for dinner, their faces all swimming together in one colourful blur. I remember snapping out of it just enough to walk the twelve minutes between the mess and the River Station, successfully avoiding snake-bites, ants and stepping on frogs. I remember the room, changing into something comfortable and then finding myself in bed. I had been more or less awake for forty-eight hours and was severely jet-lagged to boot; I was so far into the realm of exhaustion I lay in bed for nearly half an hour before sleep came.
The last thing I remember is an orchestra of frog calls and cricket-song outside my window, the music of this magic kingdom all around me, as I succumbed at last to the deepest of deep sleep.
Header Image Credit: Dr. Sabine Wintergerst
Shambhavi’s stories from the Costa Rican rainforest are published as a four-part series here on Amicable Scientists. This is part two; do check out the other parts as well!
Guest post written by Shambhavi Chidambaram.
Shambhavi (AKA Sam) is a biologist studying animal behaviour and neuroscience at the Humboldt University, Berlin. When she’s not chasing bats or running trails, she’s usually busy hunting for a perfectly-tailored humorous metaphor. Science writing for her is an art; she believes her work is done when anybody who reads her pieces has not only learned something fascinating but feels smarter in the process. While Sam mostly writes about biology and Open Science, she’s always keen for new ideas. You can follow her on Twitter at the handle @Quidestvita.