Leafcutter ants

Near the upper edge of our research area, Alex pointed out an opening in the forest canopy above and the sunlight actually made it to the forest floor here where it shone on a massive dirt hill. The hill and the opening in the canopy were the work of leaf cutter ants; they had stripped the trees of their leaves above their huge colony. These ants forage into the vegetation, cutting off bits of leaves and bringing them back to their nests. It is said that the ants can defoliate a small tree in a single day. A web of ant trails spread out into the forest, each trail swarming with a line of ants coming or going. Some trials went up the trunks of the massive trees near the colony.

Large soldiers ran along the trials guarding the more numerous workers. Worker ants were carrying pieces of leaves as large as their own bodies. From a distance these trails looked like small streams of green leaves moving along toward the colony. The worker ants ran along the trails back inside the nest, left the leaves, and then scurried back the other way for more. The soldiers were always patrolling for predators that might eat the workers, including ants from other colonies.
Some smaller ants seemed to be hitching a ride on the backs of the ants that carry the leaves. My first thought is that these were the lazy ants. It turns out these are small soldiers that are the first line of defense against attack. They run along the trial unassisted but they also apparently ride on the back of the workers to fight off parasitic flies that try to lay their eggs on the ants’ heads.

Leafcutter ants cannot get nutrition from eating the leaves themselves, and tend gardens of fungi that grow upon the leaves taken into the chambers within the ant hill. Deep in the colony there is an even smaller bodied ant that tends rooms where the leaves are inoculated with the desired fungal food. The smallest bodied ants tend the fungi on the leaves, tend the larvae and attend to the queen.

The rooms below the jungle floor are the optimal humidity and temperature for the fungus. The ants weed other kinds of fungus and bacteria out and eat their preferred crop of fungus from their dark gardens. The ants also have bacteria in special glands that excrete antibiotics that keep the food fungi from being overgrown. Species of leaves that do not allow the proper fungi to grow are removed, and somehow the workers are signaled not to collect that species any more. If leaves that are growing the desired fungi are removed from the colony, the species of fungus that the ants like to eat is quickly overgrown by others. When a winged queen leaves to mate and start a new colony, she takes a bit if the fungus with her to start the new colony. The fungus would not compete without the ants, and the ants could not survive without the fungus, yet another example of coevolution.

The ants continually replenish their gardens with fresh leaf clippings for the fungi and remove the waste to the outside of the colony. The large dirt hill is made up of soil particles from the excavation of the colony and waste from the colony. Humans are not the only species that has had an “agricultural revolution”. When jungles are cut down the hills remain and can be a hazard for livestock. When cattle walk over the once active ant hill, it can collapse into the large area of caverns excavated below and a cow can become trapped. The ants damage crops and their colonies can damage roads.

These ants are common in the tropics and there are 41 species from two genera of ants, and they tend any of several species of fungi. Termites and ambrosia beetles are the only other insects known to tend fungi. This species is a fascinating result of evolution of social insects, with the adaptation to use fungi, the bacteria that helps maintain the fungi, and the six morphologies of ants all in the same species inhabiting the same colony (the smallest workers inside the nest, the slightly larger soldiers outside the nest, the still larger workers that collect the leaves, the largest soldiers, the queen, and during certain times males).

One enemy of the leaf cutters is the army ants that patrol the forest. These ants are predators that move in a continuous stream across the jungle floor. If you follow the trail of the army ants you will eventually come upon their nest. It is a bivouac that is a ball of ants as big as a watermelon suspended a few feet above the jungle floor. The queen is inside this seething ball of ants. The ants control the interior temperature of the ball by the rate they cycle to the inside. Follow the trail that leads from this ball of ants a mile or two through the jungle, and you will find the next bivouac with the next queen. These ants move through the forest, occasionally in swarms. The ants kill every insect that cannot escape and will even take smaller animals. Birds follow these army ants to snatch the insects the ants scare up.

It is fascinating to follow a trail of these ants. Where they come to a place that is difficult to cross, the ants grasp the one in front of them and make a chain of ants. Several of these chains side by side make a bridge for the remainder of the ants to cross over. If leaf cutter ants are the farmers, these are the raiders. Army ants are aptly named. They will overcome any other insect colony they encounter, or any animal that cannot get out of the way, regardless of size.

From El Valle to Rio Maria

Having gotten settled into the hotel with plans made, lists created, and some materials packed and organized, the group piled back into the vehicles and headed into town for dinner. The small restaurant we went to on the main street was also a hotel that catered to young tourists. It was open to the front and to the side overlooking a lush garden. The lone server eventually showed up at our table (it was not exactly clear what took her so long as there was nobody else in the restaurant, but that is Panamanian time) and we ordered some drinks and dinner.

Panamanian food is unique; Americans might assume it is spicy, like Mexican food, but mostly it is not. As with all Central American food, rice and black beans are common. However, fried green plantains (patacones) are often served as a starch instead. Other common starches included potatoes and tortillas. The tortillas are corn patties that are substantially thicker than those common in Mexico. They are fried in oil and are very flavorful. There are a variety of meat dishes and beef is common. Chicken is served in several more diverse dishes. One of my favorites was chicken with garlic (pollo al ajillo). While most Panamanian food is not spicy, this dish is loaded with garlic, about a head of garlic per plate. Those who want chili head in their food can use the habanero pepper sauce that is regularly on the table. The food in the restaurant, while simple, was delicious.

After dinner we returned to the hotel and started going through lists of experimental equipment required for the next day. It took an hour or so to get ready and go over plans with Piet asking questions. We needed to charge up the batteries for field gear and make sure we did not forget anything because the 1.5 hour drive back to the hotel from the field site would preclude getting all our field work done if we had to return for additional equipment. After a rum nightcap, we headed to bed with plans to wake at sunrise.

It was an early start with a quick breakfast of fruit and cereal. Coffee drinkers had theirs, and I had a warm diet coke that I had picked up from the grocery store the day before, yum. We finally loaded the gear into the four wheel drive trucks and hit the road. The trucks are really well set up for the research. They are diesel, and have quite powerful engines, extended cabs, and take a lickin’ and keep on tickin’.

There was actually a road going up along the crater walls through that looked like cliffs from the hotel. The dirt road to the research site wound its way up through the inside of the crater walls and eventually crossed the lip of the crater; the entire road was extremely steep and rough.
As we worked our way up the steep valley leading out of the volcano it became evident that a number of people lived in the valley. A few miles up the road there was a small store and a school. A small soccer field clung to the edge of the hill. A couple times a day, a small bus came along. Most of the small farms up the side of the hill used foot or pack animals to carry materials in and out to the edge of the road, some all the way down to El Valle. As we wound our way up the side of the volcano the jungle became more predominant and the farms farther apart.

Eventually we reached the steepest hill on our trip. At this point the trucks had to be shifted into low 4-wheel drive, and we needed to get a running start at the hill. The trucks are old-style 4-wheel drive and we got out and locked the front hubs before starting. Some of the more nervous (experienced?) passengers got out and started walking up the worst of the hill on foot. This road went straight up the side of the mountain and had deep ruts from winter rains and other 4-wheelers. The vehicles bounced up and down and rocks shot out behind as the wheels spun. One of the drivers did not start fast enough and had to back all the way down and start again. If driving up such a steep hill was difficult, you can imagine the danger of backing down.
We finally got to the top of the hill and wound our way over the rim of the volcanic crater. When gaps in the jungle allowed, we could see all the way down to the coast, and other hills and mountains in the distance. The view was spectacular. The jungle here is very thick and lush. It is a rain forest that catches moisture from the clouds that roll in from the ocean, and the trees are covered with moss, lichens, and epiphytes including orchids. This dense green vegetation occasionally opened up to frame views of a thousand foot high pinnacle created by old cinder cones (Picachao Mountain) on the edges of the volcano. Near the top there were several hundred feet of sheer vertical cliff face of rock, where the volcanic deposits that formed the ancient eroding cone were exposed, otherwise the jungle clung to the cliffs and hills. Flocks of parrots flew across in the distance. A small lake was nestled into the bottom of the pinnacle, this lake had formed when a secondary explosion opened a crater that subsequently filled with water.

After working our way a few miles down the outside flank of the volcano we started to catch glimpses of the valley for the Rio Maria, our research stream. The stream originates high in the steep outer walls of the ancient volcanic crater, as the rivulets combine it forms a large valley that winds its way down the mountain across the coastal plains to the ocean, 20 miles or so away. We parked our trucks near the edge of the bridge and we got out to look at the stream. The sound of calling frogs met us immediately. There were two golden frogs on the stream bank across from where we parked, and we started taking some pictures, but we needed to get our first experiments started so we did not spend too much time looking around.

Flying to Panama

Despite the facets of traveling overseas to accomplish research, we were committed to getting to the site before the frog extinction wave hit, making the necessary measurements, and going back again after the wave had passed through. Planning such a trip is not an easy task. As with all trips to developing countries in the tropics, immunizations and travel precautions were required. Packing for an extended trip is always difficult. Adding the requirement of accomplishing cutting edge research exponentially increases the difficulty.

We needed to plan the experiments in exact detail, while accounting for the inevitable contingencies that arise in the field when plans meet reality. I have driven three hours to a research site, only to turn around 15 minutes after arriving for having forgot an essential piece of equipment. The prior Panama research team had a pump break down and a student sat next to the stream for hours making exact additions of test solutions. Best laid plans go awry, which could spell disaster in places so far removed from sources of scientific equipment and materials. Requirements for air travel (chemicals cannot be packed in suitcases so must be ordered by an institution in Panama) compound the situation. Travel restrictions following terrorist attacks now preclude carrying significant amounts of fluids onboard, yet solvents and chemicals that cause concern are required for our research.

Not only does is planning required to get research equipment overseas, but also arrangements must be made so samples can be brought back. It is difficult to keep a significant amount of sample material frozen during international travel. Only very small quantities of dry ice are allowed on airplanes and many samples are unusable if they thaw out. Also, permits are required to remove biological materials from other countries and transport them into the United States. Permits necessitate a lot of advanced paperwork, planning, and waiting.

Restrictions on bringing biological materials back into the States are reasonable; incalculable economic and ecological damage could result if the wrong pest was released into the US. It has happened before, and will happen again. Take for example kudzu, water milfoil, purple loosestrife, zebra mussels, and many other nuisance species introduced into the states. People try to smuggle all kinds of animals and plants across international borders. Restrictions are also in place to stop trade in endangered species, living or dead.

Pieces of equipment absolutely essential for successful completion of experiments must be carried onto planes. This expensive equipment could be lost in transit or damaged by inattentive baggage handlers. In simpler times carrying undefined, but complex electronic equipment onto airplanes was not problematic. Our $8000 oxygen/ temperature probes with data loggers are long, bazooka-like tubes crammed with electronics. These tubes are guaranteed to catch the attention of airport security. Every time we try to check into a flight with them, we are questioned and searched.

We made it onto the plane. Lists had been made and checked, experiments designed and discussed, travel arrangements made and verified, equipment checked and packed, and the adventure was beginning for real. The plane took off, and we all worked on papers or other materials to offset the time we were losing to a day of travel.

We had left our comfortable homes typical of the middle class in the United States, and arrived in Panama City around 10:00 pm after a long day of travel. I had started at 5:00 am. We boarded the plane in North America in February, wearing jeans and long-sleeved shirts and stepped into a hothouse climate as we exited the airplane.

The wet tropics smell unique. If you have never smelled it before, it is hard to describe. If you have smelled the tropics before, the sensation rushes back at you every time you return, like the smell of grandma's closet never quite leaves you. It is a sweet funk that never develops, even in the summer, in temperate climes. It is not the reek of party effluvia that courses through Bourbon Street, but part of that odor is there. The odor, in part, is spiced by the perfume of tropical flowers that always bloom where there is no winter. Flowers that would smell like sleazy perfume in a cheap bar, were they not the real thing. The odor is part mashed bananas and citrus, slightly fermenting. The smell is mixed with the musk of fungus and rot encouraged by moisture and continuous temperature optimal for growth of microbes.

Humidity envelops the traveler immediately as they leave the confines of the temperature controlled jet. On my walk into the terminal, the heat and humidity, the smell, and the language on the signs and of the travelers in the airport affirmed that I was not in Kansas anymore.
We stumbled through immigration and the Panamanian officials only took a cursory look at our passports. They obviously wanted to go home and we were clearly not a threat. We made our way to the baggage claim, where we met with some of the members of the party who were already in Panama City, Roberto Brenes (a student from Matt?s department), Edgardo Griffith (hired to live in Panama and help with the project) and a couple of temporary workers on the project.

Edgardo made a strong impression at first, but I did not realize he would end up being one of the central figures in this story, and that we would make a strong bond of friendship over the next few years. Edgardo is a large personality, so difficult to tell how tall he is. He has dark skin, curly hair, liquid brown eyes and a huge smile with prominent white teeth. He wears the clothing of youth with large sagging shorts and t-shirts. Edgardo has the Creole look of Caribbean jambalaya heritage, difficult to put a finger on, maybe some African, some native Indian, and some Spanish. Whatever, I suspected that he has little trouble getting noticed by women. More importantly his gregarious smile puts everyone at ease immediately.

There were lots of bags and it was to be expected that it would take awhile to get them all. After the last bag came off the carousel, mine still had not appeared. Shoot! Immediately I started thinking through what equipment I had that we might have to do without. I was glad that I had carried on my digital camera and wished I had carried on my toiletries. It was obviously going to be a late night because we needed to fill out the baggage tracking forms. Luckily Edgardo helped with the baggage claim service. My Spanish is good enough to get a hotel, a bathroom, a drink and a meal with a bit of struggle and copious hand signals. Describing a lost bag and understanding how the airline would deal with it was beyond me, and the airlines had no English speakers on duty. Edgardo settled things as far as they could be settled and gave them all our Panamanian contact information.

A motley crew

The immensity of the loss of an entire group of animals was abstract to me, until I took my first trip to Panama and saw a jungle stream teeming with so many types of frogs I had never seen before in my life; so the story begins with the trip to get there. Most of our research group met in February 2006 in the Atlanta airport to fly to Panama. This was an eclectic group of individuals who are science nerds (Ph.D.s), globe trotters, adventurers, and generally workaholics. Our common bond is a drive to understand the natural world. Everyone in the group has research experience in aquatic ecology around the world; studying streams is the thread that flows through all of our lives. Matt Whiles, Bob Hall, Alex Huryn and I were the lead researchers that traveled together on this trip.

Our connection in Atlanta was tight, and a bit of running was required to make it from the domestic terminal to the international departure gates. Bob Hall is the kind of person who is amusing to watch run for an airplane. Although I am told he is an excellent skier, he is tall, gangly and awkward looking when he runs, like a camel or a stork. He has the look and the accent of an Ivy League aristocratic intellectual. Bob looked a bit worse for the wear because he had recently returned from a research trip to streams in Venezuela and had not yet decompressed from that experience. He had a touch of the Chavez’s revenge as well.

Currently, Bob is an Associate Professor at the University of Wyoming. We have been friends since we met years ago in the North Carolina Adirondacks. We were attending a workshop to explore the use of stable chemical compounds to trace movement of elements (nitrogen) in streams. This new technique opened up an extremely productive area of research. We could use it to dissect out the basic processes that nourish all the plants and animals living in the streams. The method ultimately allowed comparison of streams from the tropics to the tundra, and resulted in a large project and ultimately a publication in the prestigious journal Science. Many investigators never are able to publish in this journal, as it is one of the top scientific outlets in the world and extremely competitive to get papers into.

It was our expertise in this tracer method that prompted Matt to involve us in the Panama project. In North Carolina, Bob and I hit it off immediately when we discovered our shared interest in home brewing. He had brought several small kegs of some of the best and more exotic beer I had ever tasted, a fact guaranteed to make me sit up, sip up, and take interest. Bob has since published some of the seminal papers on how animals and other organisms mediate movement of nitrogen through stream environments.

Alex Huryn was at the gate when I arrived. Alex is tall and slender, with a matching ambling bearing, thoughtful personality, and a preoccupied air. Many ecological researchers of my generation never left the 1970’s with regard to their hair, and between Alex’s brown hair over his collar and a substantial mustache, it was unlikely that he would be mistaken for a businessman outside of the silicon valley. He has studied stream invertebrates across North America, including the tundra of Alaska. Alex did stints in New Zealand and Maine, among other places, before he landed at the University of Alabama. Like so many ecologists with a pedigree from the University of Georgia (Matt and Bob included) he has a reputation for top level ecological research and partying hard, presumably to balance the tremendous intellectual and work load required to answer the questions that they doggedly pursue (or maybe that is just the excuse). They don’t call them the Georgia bulldogs for nothing.

I had seen Alex out-on-the-town at conferences. The last time I had seen him, he had crawled across a dance floor in New Orleans and bit me on the calf. The bulldog connotation again comes to mind. Before being bit on the calf, I had admired his research papers, but did not know him well. I was hoping he was easy to work with, but was not sure given our prior interaction.

Matt Whiles had a delayed flight from St. Louis and came to the gate at the last minute. He has been a close friend of mine since the 1990’s when we worked at Kansas State University together. Now he is a professor at Southern Illinois University in Carbondale. He is a very gregarious person; people are compelled to tell him their secrets for some reason, probably his friendly face. He has hair about the same as Alex, another child of the 70’s. Matt is gifted in the art of diplomacy and a perfect leader for a group such as ours with strong personalities and the professors’ common trait of always being certain of being right and ready to argue the point exhaustively.