Extinction

Dealing with extinction is difficult. All this was written because of my despair over the extinction of the frogs at El Valle, yet most of the writing dances around the actual issue. As the second trip approached, my dread at seeing Rio Maria without frogs increased. As a scientist the response is often to study the problem. Take for example cancer researchers that start a career because someone close to them is affected. Describing the science is like working harder to avoid thinking about the death of a loved one, it is ducking the fact that the frogs will never been seen in nature by people again.

The harsh reality, to me, is that most people do not care much about extinction of other species. In my introduction to biology course I ask a class of 80 students about this issue. I describe a local species that is going extinct, a small fish that is spiny and non-descript (the Topeka Shiner). I ask the class to raise their hand if they think the fish should be saved. Most of the class puts their hand up. Then I tell them to leave their hand up if saving the fish would be worth it if it required some personal expense to them. Over half the people in the class put their hand down.

A man has a business that removes gravel from some of the streams where Topeka Shiners still remain. He argues, in public hearings, that he is strongly against listing the species as endangered. He thinks that his right to make a living one particular way is greater than the right of that species to exist. He asks the crowded room, “what is more important, people or fish?” Many in the room nod in agreement with his arguments.

How willing are people to actually pay to save species? Is the life of a single person more important than the existence of an entire species? Is there a monetary value to a species? In a recent paper I wrote with my students we attempted to answer this question. The US requires recovery plans to be filed when species are listed as endangered. The average recovery cost was $732,000 per year. Some species cost much more to replace. Tens of millions of dollars have been spent on recovery of the black footed ferret. Total costs of recovery for the California Condor are in excess of $35 million over the last half century. Clearly some species are thought to be very valuable. However, putting a monetary value on species is dangerous. This sets up a situation where somebody could simply pay to be allowed to do an activity that threatens or causes extinction of a species.

Evolution is slow and mutation is random so that once a species has gone extinct, there is essentially zero probability it will ever return. The potential exception to this in the future is the technology for sequencing and synthesizing DNA is growing so rapidly that we might be able to completely recreate a species if the sequence of its entire genome is known. Scientists have already done this for bacteria. It is possible because bacteria have very simple genomes. It is not completely impossible that a complete genome could be synthesized and inserted into an egg of a similar species, allowing for recreation of an entire species. That is not possible for most species now, and probably for decades it will not be possible. For now, extinction is forever.

Current rates of extinction are thousands of times greater than rates of evolution of new species. It has taken 3.5 billion years for life to reach its current level of complexity. Over half the existing species are predicted to be gone in most of our lifetimes. Extinction is one of the major global environmental trends occurring during our lifetimes. We are living in unusual times where one species, us, can influence the entire planet. For the majority of species, we are a disaster. The reasons for this global trend and others are described more fully in my book, “Humanity’s Footprint”.

The fate of most species is to go extinct. As a scientist, I know that 99% of all species that ever existed on earth do not exist now. That fact does not make me feel better about humans destroying over half of all species on earth now.

In Douglas Adams’s science fiction novel “Hitchhiker’s Guide to the Galaxy” the planet Earth is destroyed to make way for an intergalactic bypass. The lead character escapes right before the destruction. He laments the loss of his entire planet but nobody from other planets seems to care much. The lack of interest by most people in extinction is similar; people who care about the plants and animals of the earth and are educated as to what is actually happening to them have a difficult time conveying the urgency of saving species. So many issues are deemed more important by most people, that preserving species ends up very low on the list.

I have dedicated my entire scientific career to studying ecology because I have always been fascinated by the natural world. I am a tree hugger. It is deeply saddening, both intellectually and emotionally, to know these losses are occurring.

It is curious to think about why people grieve. When a close loved one is lost, the feeling is physical. It is such intense emotion that it sweeps all else away. Yet, we know that people are dying all the time around the world, of hunger, disease, violence, and it has almost no emotional effect on most people. I think grief has deep evolutionary roots and leads to people protecting those who are related to them. That is why grief is so physical.

Little evolutionary advantage has existed for our species to protecting other species from extinction, just as there has been little evolutionary advantage to protect people we do not know well. Grief over loss of other species is intellectually driven emotion. Still, it is grief.

Utilitarian arguments for conserving diversity are good ones; species are the glue that holds ecosystems together. The next cure for cancer or some other disease may be found in an exotic organism or in the mold that grows in the dirt under your feet. Still, someday we could cure cancer some other way or find replacement species to keep ecosystems working in ways that provide benefits to humans. The ability to engineer ecological systems to perform functions for humanity does not, in my mind, make the extinctions acceptable.

The nitty gritty of science between trips

Now that Matt had secured funding for a second research trip, we had a lot of preparation to do. One of the most pressing issues was the need to analyze the results from the first experiment. This work required analysis of thousands of samples. Many hours of work to be done included the tedious processing, grinding and weighing of samples. Samples needed to be submitted for analysis and when the results were received, the data entered. Once the data were entered, we need to use the computer models I had created to calculate the results. Given the fact that I am not the world’s best modeler, the calculations were time consuming and required a good bit of data manipulation. The results of this complex modeling would tell us the flux rates of nitrogen through the ecosystem before the tadpoles were extinct.

We needed to finish this modeling and analysis in order to be able to conduct the second large experiment correctly. A romantic picture of field biologists who spend all their time tramping about exotic locales is not accurate for many of us. The reality is that we spend more hours behind computer screens than we do outdoors. The further along the career of an academic, the more time spent writing and administering. A horrible fate, being a department head or, God forbid, a dean, will suck the life out of a research career and eliminate research trips to the field for serious science.

Understanding how nitrogen moves through ecosystems provides one avenue to understanding the way the stream works to support the life that is found there, and how it influences the rivers and oceans downstream. Many scientists had originally considered streams as gutters that simply transport everything that enters them downstream. The research that I have been involved with disputes that view. The science demonstrates that it does matter what happens in the stream with respect to what moves downstream. This understanding has assumed great importance in the US because nitrogen transported out of the Mississippi River into the Gulf of Mexico is causing major environmental problems.

This nitrogen pollution that originates in runoff from cropland moves through the streams and fertilizes the waters of the Gulf. The fertilizer stimulates growth of the microscopic plants that live in the surface waters where there is light. These microscopic algae photosynthesize, grow, and eventually die and sink to deeper, darker waters. When they reach this area, the bacteria that live there decompose the sunken microscopic corpses, and in the process use up the oxygen that is dissolved in the water. Most animals absolutely require abundant dissolved oxygen to survive. Fishes can swim away from the low-oxygen water, but the invertebrates that serve as food to the fishes do not swim so well will die in the low oxygen waters. The pollution is thought to cause substantial economic damage.

Stream ecologists such as myself, Bob Hall and a group of others have determined that what happens in the small streams determines how much of the nitrogen makes it down into the Gulf of Mexico. We, therefore, need to account for how much nitrogen is held back in each stream. This is part of the reason that the methods we were using in Panama were developed.

The second reason is that the way the nitrogen is used in the system alters the ability of different animals to exist in the food webs found in the streams. Thus, nitrogen allows us to characterize properties of the stream relevant to conservation of stream organisms. This conservation has the goal of maintaining the biotic integrity of the stream. Again, the methods developed in general would be useful in the specific case of the Panama streams.

I wrote a computer model to analyze the data. Matt and Bob checked it, and Piet started running it on the data we had. He had lots of questions about the model, and some of them were related to errors he found. After hours of re-programming and discussions with Piet and Matt about how to use the model, Piet was finally able to get some results. A true picture of the importance of the tadpoles in the stream began emerging. Piet’s work with the modeling confirmed that the tadpoles were central to how the ecosystem of Rio Maria functioned. The open question was what would happen once the frogs were gone.

Now Matt had funding and the group’s preparations needed to begin for our next trip to El Valle and Rio Maria. Matt made the arrangements to fly, ordered materials, and Edgardo started working on local arrangements. Matt needed to find some new students to replace the ones who had graduated. The ball was rolling toward the next trip.

Hustling for funds to get back to Panama

The frog extinctions were starting to generate professional and public interest. Matt published results from his Panama studies done on the trips before ours in a very high profile, non-technical, ecological journal (the publicity magazine for the Ecological Society of America) and other more specialized papers from the group were coming out in the peer reviewed literature. Meanwhile Karen and Matt were receiving numerous invitations to speak at universities across the country where they would tell the story of the disappearing frogs of Panama and how the effects of these extinctions were reverberating through the ecosystems.

The research group also continued to make presentations at scientific meetings. Such meetings are great places to share scientific ideas and results with hundreds of others who are working on related issues. They provide the one time where scientific specialists are not the oddballs; nerd talk is the norm.

Matt and I attend a meeting of stream scientists every year and room together. Rooming with me may not be the most pleasant experience, but it is one way we could both use our grant money more efficiently. The day starts at 8:00 with scientific presentations till 5:00. Dinner is followed by a boisterous mixer in the meeting hall with hundreds of people discussing and arguing science. As with any large group of talking people, the volume increases to a roar. This makes for a long day, and after this Matt and I would lie in our beds and talk about science, our colleagues, and the state of the world.

Often our conversations would turn to the frogs in Panama. We kept trying to think of ways to strengthen the research. As in all science, every experiment leads to more experiments. In addition, the impending extinction of the frogs was something to worry about, even if we could do nothing to stop it. One thing we learned early on from rooming together at meetings, earplugs are essential.

One of the gaps in our research after our trip to Panama, and an issue Matt and the rest of us worried about for the next proposal, was measuring how much nitrogen is excreted by tadpoles. The tadpoles could be what we refer to as “ecosystem engineers”. Ecosystem engineers are organisms that have a disproportionately large effect on the environment and this effect cascades to the other species. Beavers that fill valleys with their dams, hippopotami grazing in fields and bringing nutrients they excrete back to the water, alligators digging water holes in the Everglades that last through the dry season, and bison eating dead grass and recycling the nutrients locked up in the grass available for the new growth of grass, are all examples of ecosystem engineers.

The tadpoles at El Valle were abundant and active enough that they could be major nutrient contributors to their streams. We were concerned with what happens when these potential ecosystem engineers in streams are lost. Some species of the tadpoles break down the organic material that falls into the stream in the form of leaves, and others clean the algae off the rocks. An interesting feedback is that the leaves become better to eat and the algae grow better when supplied with nitrogen. The tadpoles excrete nitrogen, and it actually stimulates production of their food. This excretion may also stimulate the microbes that serve as the food source for many of the tadpoles, insect larvae, shrimps, and fish in the stream. There were so many tadpoles in the streams that their effect had to be large, but how large was what we wanted to know.

Nitrogen excretion measurements were made while we were in the field with live tadpoles collected directly from the stream. The animals were placed in test tubes and then removed and released back into the stream. The amount of ammonia (the form of nitrogen excreted by the tadpoles) left after the tadpoles were removed was used to estimate the rate of their excretion. We did quite a few of these experiments streamside on the first trip with the samples returned to our rooms in Hotel Campestre for late night analyses. Our initial experiments indicated the rates of excretion were very high over the first few minutes and then decreased over time.

Bob argued that the tadpoles quit eating when they were placed in the experimental tubes and their excretion rates were slowing after a few minutes because of that. Alex and I thought that maybe stress was causing them to excrete more at the beginning of the experiment. Matt, being the diplomatic group leader, and a fine scientist to boot, suggested experiments were needed to settle the argument. This is the scientific processes. Our speculations formed hypotheses and now we needed the experiments to test them.

These discussions led Matt and Alex to run a series of experiments on tadpoles from the Midwestern US that are taxonomically-related to the tadpoles dominant at Rio Maria. These experiments proved that the higher excretion rates at the beginning were from the stress of being handled and put into a tube. Excretion rates from later in the experiment were more applicable to what the tadpoles were doing in the stream. Matt and Alex proved that handling tadpoles and putting them in large test tubes literally scared the piss out of them. These results were written up and submitted for publication in the scientific literature. They also strengthened the next proposal and would guide our experiments if we got funded to go back to Panama.

Another five months went by and the proposal was rejected again. This was extremely disheartening because once again, the reviews were fabulous. Matt called the program officers at the National Science Foundation to try to figure out how to get the proposal funded. The funding situation was getting dire because Piet’s and several graduate students’ salary depended upon continued funding.

We had agreed to fund the follow-up experiments in Panama out of our own pockets if need be, but we could not expect post-doctoral researchers or graduate students already living on poverty-level salaries to do the same. Luckily the program directors at the National Science Foundation agreed to some stop-gap funding to keep the project going and allow Matt time to apply for funding in the next round. One of the investigators on the grant actually paid Piet’s salary out of her personal funds for awhile. Scientists generally don’t enter the field of ecology to get rich, and many are quite generous with their time and resources, but this was exceptional. There is a long tradition of using personal funds for research; Charles Darwin had to pay his own way as naturalist on the Beagle.

Scientists through the years have had to scrape for external funding and we were no exception. Matt and the rest of us had to strategize on how to make the proposal sexy, compelling, and stress how imperative it was to fund the research immediately. We needed to write the proposal so well that the agency simply could not justify declining to fund it. Matt worked with the group on the best way to sell the research, and the proposal was submitted yet again.

The third time was a charm. I received an email from Matt telling me to plan to travel to Panama the following February. This was very good news and just in the nick of time. Matt had scouted out one site not far from the other side of Panama City where there were still frogs and additional experiments could be conducted as part of this new grant. If the disease spread much further into Panama the work would be finished for good. The remote Darien rainforest between Panama City and Columbia presumably contains the last areas the disease has not reached, but the eastern part of it is inhabited by drug runners and rebels and is not a safe place to work without an entire protective army. Going to the Darien was out of the question; we had a hard enough time getting funding, but getting support for a private protective army was out of the realm of possibility.

The disease, and getting more resources to study it

While all the causes described above are factors in global declines of amphibians, the chytrid fungal disease is primary cause of the current cascade of extinctions in higher altitude regions throughout Central America. Every place that still has a diverse amphibian diversity associated with intact jungle is losing species of frogs.

Dr. Karen Lips has been the main scientist who has described this loss in Central America. By 2007, she had worked west of El Valle, at El Cope, Fortuna, and in Costa Rica for over a decade. She studied frogs intensively at these sites, and collected and identified as many species she could.
Karen was working on her dissertation in Costa Rica when the frogs suddenly disappeared. She was at Fortuna in Panama and the frogs vanished there. There was no obvious cause of mortality. The Fortuna site is old growth jungle, minimally impacted by humans.

Perhaps the most intense experience Dr. Lips had was in the forest at El Cope in 2004 when the disease front swept through the site. In a period of a couple of weeks most of the adult frogs died. Dead frogs were literally falling from the trees. She found species that she had never described before dying on the jungle floor. This was the first time she had seen these species because they spent all or much of their lives up in the trees where they were extremely difficult to collect.

The dying frogs all had the telltale sign of chytrid infections, sloughing skin. It is difficult to imagine how Karen felt in this situation. This was an area she had been studying for years, and she was watching the animals she had dedicated her career to die in front of her. Many people would have simply given up at this point. Karen kept going. She took samples and sent them out to experts to confirm that the chytrid was indeed present and causing the infection.

As time went on, Dr. Lips mapped the spread of the infection. It killed frogs in the high altitude rain forests in a wave of infection spreading generally from north to south in Central America (but from west to east in Panama because of the orientation of the country). The disease apparently can infect, but not kill lowland species. It is not lethal but can spread through these populations in warmer areas. When the disease is passed to the next mountain range where the temperatures are lower, the disease becomes fatal and extinctions begin again as it sweeps through populations of susceptible frogs.

There is no known cure for the fungal disease in the wild, but infected individuals can be treated with chemicals in the lab if they are not too far gone. Presently, the only way to save susceptible species from extinction is to collect them and grow them in aquaria where they are not exposed to the disease. Tadpoles have been re-released into the wild a few years after the disease has killed all the adult frogs. They die from the disease when they metamorphose and emerge as adults. Apparently, once an area is infected by the chytrid, the deadly fungus remains even if the frogs that it infects are gone.

Karen was a colleague of Matt’s at Southern Illinois University and she got Matt interested in the ecosystem consequences of the loss of these species. She knew the Central American frogs as well as anybody, but did not have the expertise in stream ecology to assess the effects on the other plants, animals and microbes in the streams.

Matt had the expertise in stream ecology, and his lifetime interest in herpetology (he has kept poisonous snakes since college) drew him into the project. Matt takes vacations to the deserts of Arizona and New Mexico to see snakes and lizards; his idea of a good time is turning over rocks to see what is under them. Even after he got bit (tagged) by one of his “pet” rattlesnakes he still kept them as pets. It was not until he had children that he thinned back his considerable collection of venomous snakes.

In one of their discussions, Karen told Matt how the rocks at Fortuna had gotten slippery and greener after the disease hit. At that point a light bulb went on and Matt realized that the loss of the extremely high density of tadpoles that occurred naturally in the streams could have important ecosystem consequences. Karen got Matt to go down to Panama and see her sites, and Matt cooked up the idea of assessing the ecosystem consequences of frog extinctions.

All researchers involved with this phenomenon realize the necessity of rapid work on the frog populations. Researching the Panamanian frog extinctions is essential because there will not be a second chance. Once the tadpoles are gone from a stream, they will not be back. This was a problem Matt could not ignore. Practically, this meant obtaining funding to work on figuring out the consequences of the disease that was killing the frogs. Now, the first round of that funding was almost gone, and more was needed to keep the research going.

Matt’s proposal to continue the work previously funded by the National Science Foundation received excellent scores, but it was rejected. This was not completely unexpected, but was still very disappointing. Less than five percent of the proposals in the competition were funded. Only one out of every twenty proposals written by the top academic researchers in the world was selected for funding by this program. The National Science Foundation funds the vast majority of the basic ecological research done in the United States.

The rejection put Matt in a difficult position. He needed to re-submit the proposal immediately to meet the next deadline (proposals were only evaluated every 6 months) and it was difficult to decide how to revise the proposal because the reviews were so positive. Nonetheless, he strengthened and re-wrote the proposal in only a few weeks. After thorough review by all the official project investigators (Karen Lips, Cathy Pringle, Susan Kilham) and associated participants (Bob, Alex, and me), it was sent off. The clock was ticking, and longer delays would make research impossible.

Science is not only about writing good proposals, but also about self promotion. When funding is so competitive, only the researchers that are able to publish their work in the top science journals in the world are able to continue getting funded.

Peer reviewed publication is the ultimate yardstick of scientific success. The system is set up to increase the probability that only the most robust and exciting science gets published in the journals. A scientist or group of scientists writes a paper, and then submits it to a journal. The editor at that journal reads it and decides if it is worthy for review. If it is, the editor obtains 2-4 reviewers to look at the paper. Each reviewer spends hours looking at the paper and searching for the tiniest flaw. They are also asked to rank the importance of the work (more subjective than answering the question was the work done soundly).

The editor reads the reviews of the papers and decides if it should be rejected, accepted, or to ask the authors for a revision that will be reviewed again. If one of the later two decisions is made, the paper and the anonymous reviews are passed back to the author who is invited to re-write the paper. This is a painstaking process but it does lead to a high degree of certainty that work is done well before it is published.

Species extinctions

Of all the factors harming frogs and other species, the most ubiquitous and devastating is habitat destruction. Humans are radically altering more habitats than ever. Forests are cut down for lumber and turned into pastures or agricultural lands. Grasslands are plowed for agriculture leading to erosion and subsequent siltation of streams and lakes. Reservoirs flood streams and overuse of surface water and groundwater dries vital habitats. Wetlands and ponds are drained or filled for other uses. Urbanization, suburbanization, and exurbanization (domestic development outside of the suburbs) are destroying habitat for many species. Most land suitable for cultivation has been converted to cropland. Aquatic and terrestrial habitats are under assault every place on earth with even moderate human population densities.

These trends of global impact are global, with loss of most of the area of tropical rain forests (one of the top areas with biodiversity) predicted in the next few decades. The habitat destruction is causing extinctions at far greater rates than evolution can replace the species. I argue in my book, Humanity’s Footprint, that the pressures on natural habitats will intensify as population grows and our insatiable appetite for ever greater resource uses increases. Without drastic changes in the way we treat the natural habitats, extinction is inevitable for many species.

One of the strongest results of ecological theory and field research is that the number of species found decreases as the area of the habitat is decreased. Small islands have few species relative to continental regions. We know if we decrease the total habitat by 90%, we will loose around half of the species. Habitat destruction, even if it does not destroy the entire habitat, creates small islands of habitats. Ecological principles tell us that these small islands cannot support as many species as one very large area of natural habitat.

Frogs are but one of the species threatened by habitat loss; habitat destruction is a primary cause of a very rapid ongoing major extinction of plants and animals on Earth. This extinction is one of the 6 mass extinctions in Earth’s 3.5 billion year history. About 65 million years ago an asteroid slammed into the earth causing loss of about half the species in the oceans and many terrestrial groups of organisms, including the dinosaurs. Around 200 million years ago massive volcanic activity caused another mass extinction, and 250 million years ago 95% of Earth’s species were lost (the exact cause has not been determined). About 360 million and 440 million years ago there were two more mass extinctions.

Back to the species area calculation and how this influences extinction. Considering it is likely that we will decrease habitat by 90% in the speciose tropics, and that carbon dioxide increases in our atmosphere will continue to acidify the oceans and ultimately make it difficult for corals to survive in a warmer ocean, humans are causing an extinction that will rival other major catastrophes on earth.

The loss of amphibians has been compared to the loss of the dinosaurs. That was the last time a major taxonomic group was almost completely removed from the entire Earth’s fauna. The amount of terrestrial and aquatic habitats humanity conserves will ultimately determine the number of species that survive into the anthropocene (the current geological era of the Earth’s history where humans dominate the biosphere).

Amphibians arose around 400 million years and made it through four all four major extinction events that occurred since they arose. Modern frogs arose during the period dominated by the dinosaurs and survived the extinction that eliminated the dinosaurs. Now, amphibians, including frogs, are some of the hardest hit species of the current (human-caused) mass extinctions.

The Global Amphibian Assessment, the effort of a large international group of herpetologists, estimates that one third of the 5,918 known species of amphibians are endangered or extinct. In Panama, 55, or over 1/4th of the species, are threatened or extinct. Habitat loss and degradation affect almost 4000 species globally. Pollution is the second most common threat, and unknown causes, fires, and invasive species follow. Most of these causes are controllable or reversible. Disease is not.

No one factor can account for the disappearance or decline of frog species around the world. In some areas that seem pristine, there have still been substantial losses of frogs. In other areas the effect of chytrid fungal disease, UV exposure, pesticides and herbicide pollution, or habitat destruction are obvious. In most cases multiple impacts are occurring. Whatever the cause, frogs are becoming rare or extinct.

Amphibians are excellent indicators of ecological health. They are commonly surveyed by field biologists to indicate if an environment is degraded. Frogs and salamanders are among the first organisms to disappear when environmental damage occurs because most of them need both terrestrial and aquatic habitats, and their eggs develop in such an exposed fashion. Lakes, streams and wetlands where eggs and tadpoles develop integrate all the processes occurring in the stream.

Humanity should be deeply troubled that an entire group of organisms is disappearing from our planet, if nothing else this could indicate that the fundamental ability of earth to support us is being damaged. A broader moral interpretation, that other species have the right to exist, or for some, that humanity was placed on earth in part to take care of creation, provides reasons, other than the purely utilitarian reasons, to be concerned about amphibian declines

Introduced species and disease harming frogs

Not only do humans introduce harmful chemicals into aquatic habitats, but they also add harmful species. We have purposefully or accidentally introduced many predators that harm frogs around the world. These predators include sport fishes and other frogs. Invasive species have been deposited into aquatic habitats everywhere people live or go to recreate.

Some people think fish from one area should be transported to other areas so the fisheries can be “improved” with more desirable species. Many people prefer fish they had in the area where they grew up to the native species where they live. Thus, we have common carp in the US. This was a regular food and sport fish in Europe, and people thought it would be good idea to introduce it here. Now, it is rarely caught as a sport or food fish in the US, but has spread across the country. Carp stir up aquatic habitats, destroys habitat for other fish, and eat most anything they can fit in their mouths. Likewise, people have introduced bass into many habitats, and trout wherever they can.

We have introduced relatively large predators into virtually all major drainages of the world. Many of these introduced predators will eat frogs or tadpoles. Predator introduction is one more factor contributing to amphibian declines.
A very important example of an introduced species, with respect to amphibian declines, is the cane toad was a native to Central and South America. It has been introduced in many places in the world for pest control. It was introduced into Australia in an effort to control beetles that are pests on sugarcane. Unfortunately, the toad is ineffective against the pests it was introduced to control; the toad lives on the ground, and the beetles are higher up in the sugarcane.
Cane toads are very toxic, native snakes die when they eat the adults, and fish die when they eat the cane toad tadpoles. Having no evolutionary experience with the introduced toad, Australian predators continue to try to eat both the adults and the tadpoles. In addition, the large toad will consume any smaller frogs or other amphibians it comes into contact with as well as any other prey that can be gulped and squeezed past its jaws. The cane toad is one amphibian that, unfortunately, is not in decline.

Bullfrogs have spread from Central and Eastern US all the way to California. Because its eggs and tadpoles are not palatable, this is one of the few species with tadpoles that can avoid being preyed upon by fishes. Being the largest North American frog, bullfrogs can ingest mice, other frogs, toads, worms, salamanders, and many types of insects. These frogs may be hastening the disappearance of some rarer species of frogs, particularly those found in California. The bullfrog is resistant to the chytrid fungal disease to which many other frog species are susceptible. It may actually serve as a reservoir to move the fungus around (known as a vector to epidemiologists). Introduced species not only include animals, but also include diseases.

The chytrid fungus, Batrachochytrium dendrobatidis, causes a lethal infection to many species of frogs. The disease could have initially been spread by African clawed frogs, although multiple introductions have probably occurred. These frogs were transported around the world to be used for pregnancy tests and as research species (such as in the work of Dr. Hayes mentioned previously). The theory is that some frogs escaped and then passed the disease on to local amphibians. The African frog and many frogs from warmer habitats are resistant to the disease, but many other species of frogs are not. The resistant frogs can carry the disease from one habitat to the next.

The fungus infects the frog’s skin and causes a catastrophic loss of ability to control water balance across their skin; frogs need healthy skin to survive and are particularly sensitive to factors that alter the exchange of moisture and oxygen across their skin. The fungus causes the frog’s skin to thicken to the point where they suffocate. Diseased frogs look terrible with their skin sloughing and their beautiful colors hidden behind a thick layer of infected skin. The fungal disease seems to be hitting particularly hard in Central America and Australia, though these are the areas where the main study on the effects of the disease has occurred, and it is possible that other areas have also been hit that are not as well documented.

Global warming might interact with the chytrid fungal disease. Even a slight warming of climate represents a significant change in temperature in the tropics, where temperature extremes are not so wide. Warming paradoxically leads to cooler days at higher altitudes in Central America by pumping more moisture from the oceans and increasing cloud cover. Cloud cover also causes warmer evenings. Dr. J. Alan Pounds, of the Monteverde Preserve in Costa Rica (the same preserve that used to be home to the Golden Toad), found that these climate changes are creating the perfect conditions for spread of the chytrid disease. Over 100 species of frogs have probably gone extinct in Central America from the combination of local effects of global climate change and the disease. Frogs have experienced periods of warming and cooling over their evolutionary history, but never in concert with the chytrid fungus.

Human pollution and frog declines

The impending loss of the frogs in Panama led me to delve more deeply into the literature on amphibian extinctions. The decline of amphibians is global pattern that was noticed by individual researchers comparing observations from around the world. The researchers at international meetings realized that one talk after another was telling the same story, from sites around the world. Some of these sites were pristine, others heavily influenced by humans. The picture that has emerged over the last few decades as a result of the herpetologists realizing the global pattern is sobering, but is also a testament to science as an international endeavor and the broad geographic approach that leads to generalizations that could not be reached if research was constrained to one small area.

In the 1990’s, Andrew Blaustein, at Oregon State University, began to see declines in the species of frogs he was studying in the mountains of the Pacific Northwest. He understood that ultraviolet radiation (UVR) was increasing world-wide because of global ozone depletion in the upper atmosphere. Chlorofluorocarbons used in aerosol cans, now being phased out from use in air conditioners, refrigerators and freezers, enter the air at ground level and work their way into the upper atmosphere. Here, ozone that forms naturally absorbs the ultraviolet rays from the sun. The chlorofluorocarbons destroy the ozone that protects life on the Earth’s surface.

Blaustein hypothesized that increased UVR might be harming amphibians. This hypothesis was reasonable because UVR is known to cause damage to organisms and most amphibians lay their eggs in shallow water where they are exposed to high levels of sunlight and UVR. At higher elevations, UVR is more intense, plus it is possible that amphibians were already close to their upper tolerance levels before UVR started to increase. While these animals did evolve under such exposure, it was not certain if increases in the levels of UVR were responsible for harming the frogs. A series of experiments confirmed that the UVR increases similar to those caused by global ozone depletion lowered survival rates of eggs. One piece of the puzzle was starting to come together.

So this begs the question, will UVR increase or decrease in future years? The use of CFC’s has decreased since the Montreal Protocol was signed in 1991. The decline in stratospheric ozone has led to a halt in the loss of ozone, but still, almost 20 years later, the upper atmosphere has not healed itself. Now we know part of the reason why, nitrous oxide produced as a byproduct of agricultural nitrogen fertilization is also damaging stratospheric ozone. As humanity struggles to feed more and more people, we have been and continue to use ever more fertilizers. Some of this fertilizer is converted by bacteria into nitrous oxide, and this gas works its way into the upper atmosphere, destroying ozone and allowing more UVR to pass to the surface of the earth. Thus, UVR will continue to be a problem for some species of amphibians.

Subsequent research by Carlos Davidson and colleagues from the University of California at Davis established the role of pesticides in amphibian declines. This research examined the declining red-legged frog in California. Careful analyses of data on red-legged frog populations from 237 sites revealed that one of the most important factors in population declines was distance downwind from agricultural fields. Other research over last decades has demonstrated that pesticides and other volatile chemical contaminants can be transported substantial distances and in some cases concentrated by atmospheric processes. High mountain areas as well as arctic habitats are areas where volatile pesticide pollutants are concentrating. These are habitats that seem pristine.

Amphibians are particularly sensitive to these contaminants because their eggs require direct exposure to water, and water carries the contaminants from where they are deposited on land and water upstream, to the eggs. The potential for concentration of these contaminants in the food chain is well recognized; almost a half century ago Rachel Carson wrote “Silent Spring” and illuminated the propensity of these toxins to bioconcentrate and cause environmental harm. Before Silent Spring, most people did not realize that very low levels of these chemicals added to the environment could have adverse biological effects because they were concentrated by natural processes occurring in all ecosystems. Now, the effect could be harming species of frogs and contributing to their declines. Furthermore, a new and unanticipated threat of the pesticides has been documented.

Dr. Tyrone Hayes of University of California Berkeley, was conducting experiments on a common weed killer, atrazine. Seventy-seven million pounds of this herbicide are applied each year to fields in the US. The experiments were designed to detect minimum levels of atrazine which would cause negative effects on aquatic animals. In these experiments, frog eggs are exposed to a range of concentrations of the atrizine to extremely low concentrations that nobody would think had any effect on any organism.

He was surprised to find that vanishingly small concentrations of atrazine feminized leopard frogs while they were developing in the laboratory. Then, Dr. Hayes and his graduate students found similar results in field experiments. Further investigation showed that African clawed frogs exposed to water with as little as one part per billion of atrazine developed improperly, with inhibited larynx growth. A larynx is important to the males of many species of frogs because singing is how they attract mates. The question was how could these compounds be active at such low concentrations? This was a particularly vexing question because negative effects were expected at higher concentrations, and the effects diminished as concentrations decreased. Then, suddenly at very low concentrations, negative effects on the animals popped up again.

The answer is that the chemicals such as atrazine mimic hormones that all animals use in cell-to-cell communication. These compounds signal cells in developing animals to take one or another developmental pathway. The compounds are only biologically active at very low concentrations; animals only produce very low concentrations of hormones to signal developing cells. Many compounds made by humans and released into the environment mimic estrogen, a hormone with strong influence on sex characteristics of both males and females as embryos develop.
Ecoestrogens have been implicated in a number of cases of feminization of wildlife. It is not currently known how these compounds influence development of human embryos, and potential effects of ecoestrogens on humans is an area at the forefront of environmental concern. In this case, amphibians serve as the canaries in the mine; they are quite sensitive to pollutants in the water because they develop fully exposed to the water.

The increased used of fertilizers in agriculture was already mentioned, but more intensive agriculture also requires more use of pesticides. The use of pesticides has skyrocketed in the decades since their widespread introduction in the mid 1900’s, and we have fed the world in part because we have limited some pests (insects and weeds) by using such compounds. The chances that use of these compounds and their release into the environment will decrease in future years are slim.

Other aquatic pollutants could be harming frogs as well. Mercury concentrations are so high that many fish from waters in the US and Europe should not be consumed. Even fishes from the mighty and mostly remote Amazon can have high enough burdens of mercury that regular consumption is not advised (gold mining upstream causes mercury contamination). Mercury can harm all animals, and less attention is paid to frogs than fish with respect to contamination. This is because fewer people consume frogs than fish.

Back to the fertilizers, further work by Dr. Blaustein demonstrated that nitrite, a common byproduct of runoff from fertilized agricultural lands, also harms development of frog eggs. Nitrate contamination downstream of fertilized areas is common with very high concentrations in the rivers and streams of many developed lands, particularly Western Europe and the Midwestern United States. To make things worse, combustion of fossil fuels leads to substantial amounts of nitrogen deposition and causes nitrogen contamination of many aquatic habitats. The effect is particularly strong near industrial or urban areas. More pieces of the puzzle of global amphibian declines were falling into place.

Saying goodbye to the frogs

As we continued working at Rio Maria, it became more important to me to take in the experience of watching the tadpoles swarming in the stream and the constant movement of small frogs scattering as I walked down the jungle trails. This place was the “zen” of frogs and it was easy to sit and meditate on them. Our discussions more frequently turned to the impending disappearance of the frogs and the prospects for saving other parts of the jungle.

While the road to the research site from El Valle was tremendously difficult, it connected with a road that came up the other side of the volcano from the coast highway. This area up high on the slopes of the volcano had seen years of agricultural use, mainly cleared jungle for pasture. This development was patchy, but now it was being converted into high priced houses and ranchettes for wealthy Panamanians. The site also attracted retirees from the US and Europe who realized their money could buy more in Panama than it could at home. The site also attracted retired “snow birds” who migrated down to avoid the cold winter, and then closed up their homes in Panama and returned to the States in the summer. The mountain sites were attractive because of the fabulous scenery and the pleasant year-round temperatures. Not as hot as the lowlands, yet never actually very cold. The land of eternal green and spring was very attractive indeed.

The bulldozers were rolling. It was obvious that development was as much of a threat to Rio Maria as the fungus that was creeping toward the frogs, but the developer claimed that the Rio Maria valley would not be developed and the valley and its wildlife would be preserved. This was good news because habitat destruction would take the majority of the plants and animals with it, leaving only the few weedy species that could coexist with humans. Diversity would be far less than in the current jungle.

Cathy Pringle needed to get back to teaching so she took a shuttle bus to the airport. After she was gone we found a pair of her dirty shoes and socks in the back of one of the pickups. It made sense, who would want to carry wet socks on a day long travel home? We now had proof of the rumors about her always leaving behind socks and we all got a good laugh out of it. Someone in El Valle would certainly put them to good use after a good washing.

We spent a lot of time training Piet, Heidi, and Edgardo who would remain behind to finish up the work and continue monitoring the stream. They needed to learn how to collect all the samples and what to do if things did not work out quite right. It was as important to teach them the concepts behind what we were doing as it was for them to learn specific technique. What if sampling is put off for a day, is that ok? What if the pump breaks and samples cannot be filtered right away? Understanding the research allows such questions to be answered. Fortunately, we could maintain contact with them via e-mail and cell phones from El Valle.

Before we left, we also tried to process as many samples as possible to take back to the US. The routine of field work associated with this type of experiment is the same regardless of the setting. Samples need to be dried and weighed, some of them ground up. Water needs to be filtered and analyzed. Voucher specimens need to be preserved for formal identification in the laboratory. Who was bringing what sample back to the states was important and it was all recorded.

The last day at Rio Maria, we turned off the tracer drip. Then we had to wait for the lines to get cleared out, so Alex and I took a walk to the stream above. It was nearing dusk and the frogs were becoming more active. On a rock in the middle of the stream we saw a smaller male golden frog perched on the back of a larger female. This behavior is called anaplexus, and is how the frogs mate. The males are reputed to ride around on the backs of the females for up to two months before an appropriate breeding site is found. I suspect that this is just legend, but you have to admire the tenacity of the male. All the while, the male strokes the female’s chest with nuptial pads on the fingers of their forelegs. This has to be the longest foreplay in the animal kingdom. Eventually the male fertilizes the eggs and the female lays them. This extraordinary courtship continued in spite of the impending demise of these frogs.

We felt like this was the last we, or anybody else, would witness this behavior of this species in the wild. The last chance to see can be profound, and Alex and I were both lost in our thoughts about what the image meant to us.

The trip back to the US from El Valle was uneventful, with a good shopping trip to an artesian market and a night at a very good seafood restaurant in Panama City. We got up very early the next morning to give us plenty of time to make our 8:00 am flight.

The flight back was ordinary; it was amusing to watch Bob talk his way through US customs with more than his allotment of liquor to avoid paying import tax. The customs guy told him not to ever do it again, but let him through. If he knew how many more bottles Bob had in his checked luggage, he might not have been so nice about it. The best strategy in customs is, never lie and never give more information than asked for. Considering we were bringing samples back into the country, even though it was completely legal to bring the types of biological samples we had back, an overzealous customs or agricultural products inspector could delay us long enough to cause us to miss the next flight out.

Before I knew it, we were back in the US and into the world of strip malls and fast food. Culture shock, even though we were only gone for a couple of weeks, still make a mark. The main objectives of the project now fell to Matt and Piet. Matt needed to obtain more funding to repeat the trip after the disease swept through Rio Maria and the El Valle region, and Piet needed to work through most of the samples we brought back. I had my expensive bottles of rum, a batch of digital photos, and memories of Panama, El Valle, and the frogs of Rio Maria.

Our first task on the project after returning was to obtain funding to get back to Panama and complete our experiment. We agreed that we would find a way to bootleg the work out of other projects if we needed to, but could not do as good of a job without substantial research funding. This job fell to Matt because he was the leader and wrote the first grant. He was a bit spoiled because the first grant had been funded the first time it was submitted, and it was also the first grant he had submitted to the National Science Foundation as lead investigator. Such success is rare, but we were optimistic about requesting the next round of funding. The additional funding seemed highly deserved because of the urgent nature of the research, the unique and powerful angle of using the nitrogen tracer experiments to test how the effects of tadpole extinctions in the streams cascade through the rest of the ecosystem, Matt’s skill at grant writing, and the assistance of the rest of the group.

The next deadline for grant applications was 5 months after our return and Matt wrote the proposal and circulated it around to the rest of the group for their input via email. Writing a grant proposal such as this is not a trivial amount of work. The body of the proposal was 15 single-spaced pages, and including all the necessary information to satisfy the dozen or so reviewers in this length of document is quite a trick. Completion of many pages of forms is also required and every detail of the proposal must have references from the scientific literature to verify statements and show that adequate procedures will be used. Multiple investigators from multiple institutions requires numerous budgets each with their own requirements and bureaucracies that need to be navigated for many signatures. After a long process, the proposal was polished up and submitted. Then we had to wait for the 5-6 months it takes for grant proposals to be processed.

The jungle stream at night

The next few days were filled with technical details of working in the field and doing lab work in the evening. We got time to call our families at home and eat some nice meals. A highlight was when Heidi and Scott Connelly took Piet and me on a night herping (looking for amphibians and lizards) expedition. I had been taken on a night-time herping expedition in Costa Rica many years before.

The expedition leader on the Costa Rica trip was a professor with lizard-like eyes; they bulged out and he rarely blinked. He carried his cigarettes in one plastic bag tucked under his belt. He had another large bag stuck in the other side of his belt to hold the snakes and frogs he caught on the trip. His plaid polyester pants tucked into the top of his rubber boots and shirt button down polyester shirt, as well as his umbrella, seemed odd at first but his enthusiasm for the animals was contagious. We had a fantastic night tromping through the jungle swamp. He would shine his flashlight and catch the flash of reflective eyes and crash into the swamp after it. He would come back beaming with a poison snake in his hand, or a frog or lizard. First thing the next morning we looked at all our prizes. I jumped at the opportunity to go night herping again.

We secured our headlamps, grabbed our cameras and drove to a local stream as the sun went down. As we walked to the stream Scott and Heidi talked about the incredible diversity of frogs in the region.

In addition to the golden frog are several species of glass frogs. These frogs are clear because they have little pigmentation. You can see their hearts beat by placing a light behind them. They lay their eggs on leaves overhanging the stream where the eggs are less susceptible to egg predators. When the eggs hatch, the tadpoles drop into the stream.

We talked about the tadpoles that live deep in the leaves at the bottom of the streams. Accumulations of leaves on stream bottoms are very low oxygen habitats and the tadpoles have tremendous amounts of hemoglobin (the protein that caries oxygen in our blood and that of other invertebrates). They are bright red when exposed to oxygen. This is a somewhat common adaptation among animals. In temperate lakes, midge larvae known as blood worms inhabit the low-oxygen sediments. They are mostly colorless in their native habitat, but when they are exposed to air at the surface or highly oxygenated water, they turn bright red as their abundant hemoglobin binds all the oxygen it can.

Panama has 195 documented species of amphibians. This is over half the number found in the US in a country slightly smaller than the state of South Carolina. Thirty four of these species are found nowhere else (are endemic) and most are restricted to Central America. Panama is an amphibian-lovers paradise and El Valle has historically been a Mecca for people wanting to see Panamanian frogs and other amphibians. Frog societies plan meetings and collecting trips commonly with El Valle as their base of operations.

During the day, brightly colored toxic frogs such as poison dart frogs are common. These frogs practically glow in the low light of the tropical forest. Their bright colors are a signal to predators that says “I am poison, eat me and you die”. Other species, also brightly colored, look like poisonous species, sending the same signal to predators, but are not toxic. This mimicry allows the frogs to avoid predation without having to synthesize costly toxic chemicals. The two types of frogs are balanced in population numbers, because if there are too many of the non-toxic species, predators will start eating and frog with that coloration. So, the non toxic frogs take advantage of the toxic species that they mimic. Evolution has lead to some amazing things, and “cheaters” are a fact of life!

At night the more cryptically colored frogs come out to forage. Their calls filled the stream bottom as we worked our way up the rocky stream channel in the dark. Our flashlights were reflected by the eyes of freshwater shrimps as long as your hand. These shrimp are very skittish, and they scuttled out of sight under rocks by the time we were within 50 feet. Freshwater shrimp are common in tropical streams. Some species have been taken into captivity for aquaculture, particularly in south-east asia. Some of these shrimp play the part that crayfish (crawdads) fill in more temperate streams (omnivores), but others specialize on fine or coarse particles, or algae, or other food types. The shrimp are most common in smaller streams where large predatory fish will not eat them.

Moths bigger than my hand were hanging over the stream. We saw an occasional snake foraging through the underbrush near the edge of the stream; preying on the abundant frogs. The jungle shows a whole different face at night, animals scurry off through the darkness, bats dart around over the stream, and there are spiders the size of a salad plate with eyes that glow in the darkness when your flashlight happens to strike them. Scott and Heidi discussed how the frogs probably would not be around the next time I came back. We left the stream to get back to our hotel muddy, sweaty from our walk, and thoughtful.

El Valle Open Air Market

At first glance we could tell that enough rain had not fallen to cause a flood bad enough to scour the channel, wash away our expensive equipment, and scour the channel badly enough to ruin our experiment. Several large yellow and black frogs jumped on the stream banks; the golden frog of Panama was doing well here for now. They were not concerned about our presence. We walked another quarter mile up the slippery muddy trail to where the pump was dripping in the tracer solution at a constant rate. We changed the battery and added fresh tracer solution. It was good to get the weight of the tracer solution out of our packs. Tadpoles were swarming in the stream as they had been the day before, the slightly increased flow and cloudy water from the rain was not bothering them apparently.

Everything looked in order so we ate lunch and headed back. By the time we started back the rain had cleared and the tropical sun had started to beat down. It heated up quickly and the road was steep from Rio Maria up to the volcano rim, to where it would drop back down into the crater and wind down to El Valle. We started regretting that we had not thought to bring more drinking water. We slid our way down over the slippery clay on the steep hill that had stopped the trucks in the morning. Our ride had not arrived at the bottom of the hill, so we started down the road toward the hotel. We hoped we would not have to walk the entire 5 additional miles back without a lift. After a bit we reached the area where there were farms and passed a place where a citrus tree had dropped its fruit into the road. These green fruits were not quite grapefruits and not quite oranges. Nonetheless they were a welcome and delicious source of liquid as we made our way toward El Valle. Another half mile down the road one of our trucks pulled up and we rode back.

That afternoon it was still sunny and we made our way down to the open market in El Valle. It is a mixed tourist and local market with booths selling everything you would need to live in the area, as well as many trinkets, locally produced and imported art objects aimed at tourists. While some may consider a department store a modern invention, the city market has a comparable array of goods crammed into the same amount of space; many more merchants participate in selling goods. We bought more food and some gifts for our families. I noticed fruits not common in the US (custard apples, nance) as well as those that are (pineapple, oranges, and grapefruits). The produce was fresh and much better than commonly found in large supermarket chains.

Items mainly for tourists included the well known traditional molas, an appliqué tapestry made by Kuna Indians and transported from the Caribbean coast to the north. Tagua nuts are about the size of a lemon with an ivory colored interior that hardens after being carved and exposed to air. The tree in native from the Southeast of Panama into Northern South America. Before plastic buttons, the nut was commonly used to make buttons that looked like ivory. Using these nuts to produce statuettes is an environmentally responsible solution for those who like ivory carvings. Commonly, intricate animals are carved in the tagua nuts and the carving is painted.

Natural animals are a common motif in these artisan-produced objects and most are fairly realistic. Many of the Tagua nut animals are extremely accurate representations, both in terms of color and proportion (although there are some inferior products to be found as with any craft that is sold for tourist consumption). These crafts suggest that the Panamanian artists, at least, value their wildlife. If they were only carved for tourists, attention to details of form and coloration of local spiders, frogs, and snakes would be unnecessary, as most tourists have no idea what the real animals look like. There are also cocobolo carvings of animals, and palm-fiber baskets and purses.

I was particularly interested in how many golden frog statuettes were available, some were tagua carvings, but most of the frogs were cheap plastic versions. The golden frog in Panama is the equivalent of the bald eagle in the US. The population crash of the bald eagle ultimately led to banning use of DDT in the US because people were upset the national bird could be lost. The toxin DDT concentrated in their eggs and made them so thin they would crack. The US people found this unacceptable and refused to allow use of DDT.

The Panamanians are experiencing the demise of a cultural touchstone to their country, and they can do little to stop it, as will be discussed in the next chapter. I also wondered if the statuettes would still be available in a few decades and how much they would look like the actual frogs. Many of those available in the market that day were true to the morphology and coloring of the golden frog. Others were depicted smoking and drinking martinis, kitschy tourist bait. Cultural evolution and no real comparison alive in the wild could ultimately lead to only a stylized version being sold, if any.

We watched as tourists disembarked from large air conditioned busses and flooded into the market only to leave an hour later. Overweight tourists haggled with the market vendors; many had cameras with lenses over a foot long or expensive digital video cameras. It was a typical scene in a tourist town. The atmosphere was definitely more relaxed after the last bus left. It was humorous that I too was a tourist, yet somehow felt superior to these bus tour participants.

That evening, after dinner I noticed that a television in the bar across the street was playing the super bowl. Passing up this bit of “culture” from home proved too difficult and we decided to go in. Entering the bar I noticed the gangs of tough looking youths hanging around outside. There were very few women in the loud and crowded bar; obviously the few females there were attending in a professional capacity. These professionals were not the women young men would bring home to meet their mothers. In general, this was one of the rougher bars I had been in. Feeling a bit insecure, I stayed near the bar with my group and watched the game.

Suddenly it struck me… nobody was smoking. I asked about this and was told that smoking had been outlawed inside public buildings in Panama a year before. Here I was in a rougher bar than any in my small town in the Midwestern US, yet smoking was not allowed here while such a ban in my home town occurred 2 years later. Some places in Panama are more socially progressive than parts of the US. This observation led me to realize that relationships between society and health were more complex than I had considered.

Later, I discussed the idea of social responsibility for health and environment with Heidi. She has an interesting perspective having lived in Panama for the last half decade, but growing up in the US. She mentioned that the Panamanians were also very concerned about global warming and most were unhappy with the way the US has been dealing with this issue. They felt that the US was burdening them with environmental problems associated with global warming without spreading the benefits of their extravagant lifestyles to the Panamanians. Essentially they felt the US people were burning the fossil fuels and they were paying the price for our consumption.

I don’t remember who won the football game. I do remember that the next morning I got my luggage! We had another working pump and I had some clean clothes. The clothing I missed most, other than clean underwear, was the quick dry pants. Quick dry clothing in the tropics is far superior to denim jeans. The thin synthetic fabric protects you from insects and the sun, but is not too hot. Given the amount of rain in a rainforest, the quick dry feature is advantageous. Plus, my quick dry pants looked a good bit nicer than the droopy jeans I had been wearing non-stop for the last 5 days.

Bannanas, filtering and lost luggage.

Working in the dark is difficult at best and potentially dangerous in the jungle. The road back would be even more treacherous in the dark than the nighttime jungle, so we finished up in time to get our gear back into the trucks and drive back to the hotel before dark. Edgardo called about my luggage when we returned, but it had not yet been found. Back at home my wife had been working on tracking down my luggage, and she had made no progress either. At this point we also received word that a member of our planned research group, Karen Lips, had also lost her luggage and was staying in Panama City to attempt to retrieve it.

One last member of our research team, Cathy Pringle, had arrived at our hotel that afternoon after coming in on a different flight. She is an internationally respected researcher, a professor at the University of Georgia and has been more involved in advancing the study of tropical streams than almost any other researcher in the world. She has worked across the Caribbean, in Costa Rica, Panama, the South Pacific and Madagascar.

If somebody in the research community mentions “tropical stream ecologist”, Cathy is who comes to mind. She is an innovative person who knows how to get the resources she needs to do the research. Her brash and gregarious nature and deep desire to understand and preserve tropical streams have taken her to parts of the world that few have experienced. These qualities make her an extraordinarily interesting person to work with. She is an original and hard working researcher. I had worked with her for years on issues related to our stream ecology society. Among other things, Cathy loves little tasty tropical bananas and shopping. She has a twinkle in her eye and a mischievous nature, as well as a reputation for leaving pairs of dirty socks behind everywhere she travels. She also is the exception to the rule about not wearing sandals while working in the jungle.

Speaking of dirty clothes, mine were becoming a bit dodgy; I washed out what could be washed and we headed into town for dinner. After dinner we broke out a little rum, mixed it into some pina-guava juice, and got down to doing our chemical assays. Some of the local help thought the party would be fun but when they realized we were actually doing lab work and calculations for our experiment the next day, they drifted off to their own rooms. After a late night of planning, we turned in, thinking about our getting going early the next morning.

I pulled on my sodden clothing the next morning, followed by the usual fruit and cereal breakfast, and of course, my diet coke. The coffee drinkers were enthusiastic about the fantastic Central American coffee, and I almost regretted not having taken up the habit, the smell at least was quite pleasant. After repeated runs through our equipment lists, and a longer delay than we planned to discuss the experiment (more questions, it turns out Cathy, as well as Piet, is really big on questions), the group piled into the trucks and we started back to the field site. Matt had mentioned to me before we left the States how the steep rocky roads started to wear on you after a week, I was starting to understand what he meant, and this was only the second day of driving stiff-suspension 4 wheel drive trucks bouncing up and down the hills.

We got to Rio Maria without major problems and carried our gear to the upstream point of the nitrogen tracer experiment. We needed to pump trace nitrogen into the river continuously for a week, and that required us to carry 5 gallon carboys full of the chemical that we had dissolved in water the night before, a half mile up the stream. Five gallons is over 40 pounds. The jungle trail was always slippery, and the added weight of the carboys did not help. Our footwear was knee-high rubber boots which do not have the best traction. This was hard work, and we were grateful we made it before the heat of the sun peaked.
There were more samples to collect, so we had another full day of work ahead of us. The samples were taken and the tracer experiment started as planned. We had some down time between measurements and this time was used to crack open tins of food and crackers for lunch. I had brought my underwater camera and started to take pictures of the tadpoles in their native habitat.

Underwater cameras have recently become fairly inexpensive and easy to use with the advent of digital technology. They are a fantastic piece of equipment to have, even if underwater pictures are not desired; the jungle is always humid and drippy and the protection is helpful. I had spoken to professional photographers about using cameras in the tropics and they mentioned that fungus and moisture always work their way into lens systems and eventually fog them. At least the underwater cameras are protected from this and the desiccant packs placed in them help even more.

Also in down time, water samples needed to be filtered. We had only manual vacuum pumps and needed to filter large amounts of water to collect particle suspended in the water onto filters so they could be analyzed, and the filtered water also needed to be saved for analysis. The pumps kept breaking down; unfortunately my hand pump was still in my lost luggage. Emergency repairs with duct tape and epoxy were all that allowed us to keep using these pumps. Cathy Pringle is one of the few full professors I know that really enjoys sitting in the sun next to a tropical stream, eating the occasional small sweet tropical banana, and pumping water samples for hours. This is probably a good release from the hectic pace she maintains back in the states at the University running her large laboratory. We willingly allowed her be the official jolly field filterer.

As 6:00 pm approached (sunrise and sunset time are certainly predictable in the tropics) we had packed our gear and put some brush over the trail to obscure our path up Rio Maria. We knew that the thousands of dollars of gear we had up the stream would be worth nothing to the locals, but could not be certain that the gear would still be there the next day if we advertised the location where we were working. Making our way up the road carved into the wall of the extinct volcano, the setting sun illuminated the jungle draped rock pinnacle a few miles away, a breathtaking end to a good day in the field. All that was left was dinner, drinks, and more filtering and analyzing samples that evening. We also started entering data into our computers and making certain that the field notes were all organized with their data duplicated against loss.

The good news when we got back was that my luggage had been found and delivered to the bus station. The bad news was that it was Saturday night and the station was closed on Sunday. Try as we might we could not get the employees of the bus company to come in and open the station. I offered bribes, but they were worried that violating regulations would cause them to lose their jobs. My bribes were not big enough. Of course Edgardo was patiently mediating all this; I purchased minutes for his cell phone to reimburse him for all the calls he graciously made in pursuit of my luggage. The restaurant we ate at was right across the street from the bus station, so we went to look for my bag. Sure enough I could see my suitcase sitting there. My filthy jeans seemed a bit worse for the wear and did not smell pleasant. My trip mates would probably say they stunk. My suitcase sitting a few feet away, yet unattainable, did not help things much in my mind.

The next morning it was raining. Our experiment was taking place during the “dry” season, but we were in a rainforest. The rain made us very nervous because we needed to be certain that Rio Maria was not flooding and ruining our equipment and also we needed to carry fresh tracer solution and check that the pump delivering the solution to the stream had adequate power and was working properly. The clay parts of the road to Rio Maria were very slick from the rain.

Scheduling issues related to the rain caused tensions to rise that morning. Also, some of the crew was uncomfortable with the fact that all of the drivers were not experienced with four-wheel drive and manual transmissions. All our four-wheel drive trucks were manual, and driving them on the treacherous mountain roads was not a task for beginners. We got all the passengers sorted out and started up the road in four wheel drive (we usually did not lock in the hubs for the four wheeling until we got to the really steep bits but we needed it as soon as we left the pavement this day). When we reached the steep part, everyone but the drivers got out. Edgardo then tried to drive up the hill. It was a disaster. He would spin all four wheels up about quarter way and then get stuck, only to slide backward down the hill. Considering the steep drop-off on one side of the road, sliding in the mud backwards was not exactly safe. We were lucky none of the trucks, or for that matter, the people, were damaged.

Alex, Bob and I decided we needed to walk in to check the experiment. We packed up some tracer solution, batteries, sampling equipment, lunch, and put on our rain gear. A time was set for a truck to come back and pick us up. Getting up the steep bit was difficult, even on foot. The only good footing available on the greasy road was protruding rocks or vegetation growing along the edges. We slipped our way up that hill, and the next, and the next, to the top. Then we started on the road as it traversed down the outside of the ancient volcanic crater.

Every once in a while Alex would point out something interesting that I had never seen before. The guy is a fanatic for leaf-cutter ants and insects of all kinds. He has a fantastic eye for biodiversity, and by the end of the trip I realized that he is one of the best natural historians I had ever been in the field with. I have been in the field with quite a few well trained, expert biologists. We could hear birds and frogs calling in the jungle, but the thick mist obscured most of their locations. The frogs were calling even more vigorously than the day before, if that was possible, because the rain stimulated them. A couple miles later we were at Rio Maria.

Danger in the jungle

The rainforest around Rio Maria is not pristine. The area was logged 50 years or more ago. Large birds that once flew above the trees, such as the Scarlet Macaw, are gone, most likely captured by locals. No howler or spider monkeys are left in this jungle, and the collared peccary (javelina) is not found as it once was. These mammals were probably taken for food or the pet trade by people. This region is not protected and is too close to human habitation for most large animals to survive collection or hunting. Still, the small plants and animals are very diverse and the jungle here has much to offer to biophilic (biology loving) visitors.

The ability of the jungle to rebound from logging is a direct consequence of the millennia that these trees and associated plants have interacted with humans. Panama has been inhabited for at least 11,000 years. The indigenous people have a sophisticated culture, that among other things, developed unique and ornate styles of pottery. In this region, called Coclé, the indigenous culture required rotating agriculture which would have been slash and burn. The jungle in the flat parts around Rio Maria has very likely, over thousands of years, been repeatedly been cut (slashed), burned, cropped and after a few years left to return to jungle to recover its fertility.

While the jungle around Rio Maria was missing some components of an extensive, old-growth, tropical rain forest, it still had incredible diversity and beauty. Only in recent history have humans developed the machines and population densities to completely remove jungle from tremendously large areas. There is little hope the diversity will return to the areas of massive deforestation as it does to the small patches that are cleared for a few years by native agriculturists under slash and burn cultivation. We know that very plant and animal diversity could coexist with the traditional native practices, but those days are now gone.

Working in the forest requires caution. Those who work in the jungle say that falling trees and limbs are the greatest danger. If you are unlucky, one will fall and hit you in the head. If you spend much time in the jungle you will hear limbs falling, and the trees in even this re-grown rain forest can be a couple of hundred feet high, so the branches can gain considerable momentum before they strike an unlucky researcher below. Each tree limb plays host to numerous epiphytes. These epiphytes include the orchids and a number of what we commonly see as houseplants in homes in developed countries of temperate climates (for example ferns, spider plants). These plants take advantage of the limbs of the trees to grow higher in the canopy where they can get far more light than they could on the forest floor. The mass of plants on each branch grows to a greater and greater mass. Eventually the weight is too much for some branches to bear and they come crashing down.

The large trees tend to have shallow root systems that are spread across the jungle floor to intercept nutrients that reach the soil there. Tropical jungles generally have very poor soil and organic materials containing nutrients are rapidly degraded and the nutrients they contain scavenged quickly. This is part of the reason for slash and burn agriculture; the vegetation that is cut down and burned provides nutrients for a few years, but the soil is not productive so the fields are abandoned after a few years. Unfortunately, if cropping continues the soil becomes so
unproductive that not even the jungle can return.

The shallow roots are not good at holding up the trees, and this is made up for by the buttresses (broad supportive ribs) that extend away from the base of the trunks. Even with the buttresses, a large tree will fall occasionally. Because it is connected to others by dense vines, not only will it smash the trees directly where it falls, but also the falling trunk will take many smaller trees down with it.

Tarzan movies are not very realistic, but there really are vines that could support a large primate that crisscross the jungle canopy. We tested this as college students in the jungle finding vines on hills that would allow us to swing high into the air.

When a large tree falls and takes others down with it, the light gap that enters the forest will allow new rapidly growing trees to grow up into the canopy. This process is part of what leads to the tremendous tree diversity in the tropics; the light gaps promote species that would not be able to compete in the dense closed canopy of the jungle.

A newly fallen tree also attracts local people scouring the forest for exotic orchids that might have been growing high in the canopy before the tree fell. These plants can bring a hefty price. The orchids are for sale in the local markets and collectors around the world support a legal and illegal orchid trade.

There are other dangers; toxins are common. Some palm trees commonly found near the ground on of the jungle have large poisonous spikes that will cause a nasty allergic response in the impaled hand unlucky enough to grab a trunk to avoid a fall. Large garishly colored caterpillars have poisonous spines. While these caterpillars are not aggressive, inadvertently brushing against one is not advised.

Paraponera ants that crawl on tree trunks are also called bullet ants because a bite from this inch-long ant feels like a bullet and causes pain for 24 hours. Their large mandibles cause what is said to be the most painful insect sting of all; the pain results from a potent neurotoxin. Initiation rights of some indigenous South American people entail repeated bites from these ants. It is difficult to imagine being stung 20 times without screaming, but this is what is reportedly what it takes to be a man in some cultures.

Poisonous snakes are also a concern, but are less common at higher elevations. It is possible that the bushmaster, Lachesis sp., the largest (up to 14 feet long) of the pit vipers, could be encountered up to 4000 feet elevation. The Fer-de-Lance, Bothrops asper, can be found on the ground or juveniles can be found in trees. Tree vipers also known as eyelash vipers, (two species at high elevations), hang from trees. Hog nosed vipers, tropical rattle snakes, and coral snakes all can be found in Panama. All these species are poisonous and bites from some can be fatal. It is always best to watch where you are stepping and move with care when walking in the jungle. This is not sandal country (but the next day we would see the exception) and boots, not flip flops, are advised. The dry season we were in, is also the time when the bushmasters are most likely to bask near Rio Maria, so we were particularly careful to watch for these vipers.

Of course, insect-borne diseases are also a concern, as they are in much of the tropics. Diseases found in Panama include malaria, chagas disease, dengue fever, yellow fever, and leishmaniesis. We killed an Assassin Bug in our hotel room, known to be a vector of chagas disease that can be fatal if left untreated. The usual precautions against insect bites and appropriate vaccinations at least decrease the worry. If you see an Assassin Bug in your room in Central America, kill it. These issues are not enough to keep many scientists and ecotourists away. The fabulous diversity and unique area are so attractive, and appropriate precautions minimize the chances of danger .

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.

The Jungle

I needed to sit and read a meter every 5 minutes or so, and was able to observed the stream more closely. While sitting on the stream bank, the diversity of types of tadpoles was unbelievable. I had been told how many species could be found in the sream, but the words did not convey the reality. Herpetology in general, and immature frogs in specific are not my areas of expertise, so I could not identify individual tadpole species. Actually, very few people can accurately identify most of the species in these streams from the tadpoles. In our group Edgardo and Scott were the specialists and the rest of us were just learning. Still, even to my unpracticed eye there was a clear variety present.

Some tadpoles were larger than my thumb and had very streamlined bodies. These used the suckers on their mouth to attach to rocks in faster waters. A large rock could have 10 or 20 of these. The scrape marks where these tadpoles had fed on the algae attached to the rock were apparent.

Chubby tadpoles with bodies that looked like slightly flattened spheres with a diameter wider than a quarter squiggled along the bottoms of the pools. These were not extremely fast and I caught one and its body felt like a bag of water. I released it and it skittered away. I wondered how such a slow large animal could exist without being preyed upon by snakes, lizards, and birds around the stream? Perhaps the fact that they were like a bag of water indicated that there was very little nutrition to be had in one of them, or maybe they were toxic. Given the impending extinctions, it is possible nobody will ever know the answer to the question.

Small tadpoles with bodies the sizes of orange seeds were wriggling around in shallow waters. I turned over some of the large wads of leaves on the stream bottom. Tadpoles with bright red blood vessels skittered away.

The open areas of the pool were perhaps 10 feet long, 10 feet wide and a half foot deep. Every one of these areas had herds of hundreds of small tadpoles, each the size of a pea, grazing on the microbes (algae, fungus, and bacteria) that lived attached to the sand and gravel. Any sudden movement would cause them to scatter for a while and hide, only to emerge a few minutes later and continue their incessant eating. Their only job in life was to gain enough energy to emerge from the stream, morph into an adult, mate, and produce more offspring.

Ecology is full of technical words, and the film of organism the tadpoles eat that is found on the bottom of the streams is called periphyton, a biofilm, or in more old fashioned terms, aufwuchs (one of my favorite words for some reason). In some strange way these tadpole flocks (there is no technical term for a group of them that I am aware of, maybe they school like fish) reminded me of the herds of bison that roam across the Kansas Prairie grazing the grass. Oh give me a home, where the tadpoles roam! Both the tadpoles and the bison are mainly eating machines and consume for most of their time. This constant eating is a requirement for any animal that eats relatively low quality food like grass or periphyton.

Time between writing down numbers offered me my first chance this trip to contemplate the riot of diversity that is a tropic rain forest. Evolution is occurring at breakneck speed relative to temperate systems. This has led to far more complex and diverse systems than occur in temperate habits. There are so many species of plants and animals that it is difficult to know how they interact, and fascinating to consider the linkages.

Plants struggle for light and nutrients. Water is not a problem here. Trees soar hundreds of feet upward into the canopy to intercept light. The trees have shallow roots that spread to intercept nutrients as soon as they reach the forest floor in the form of a fallen leaf, dissolved in a rain drop, or in animal excreta. The trunks of trees have wide buttresses (flared ribs spreading to the forest floor) to support their tall trunks. The buttresses give the jungle floor the feel of a green cathedral. The trunks and branches of all trees are covered with vines, mosses and other plants. Every square inch of available space is used.

The forest cuts the wind so flowers must be pollinated by birds, insects or bats. Each flower has its own tricks to lure the specific pollinator it needs and to exclude animals trying to steal the reward they offer to the type of pollinators they are trying to attract.

Exotic orchids offer odors as rewards that iridescent bees use to attract their mates. Each species of bee has its own cocktail of scents it harvests from different orchids, pollinating the flowers as they collect their scents. Humans were not the first species to discover the use of perfumes harvested from the surrounding to attract the opposite sex.

Some species of orchids are shaped to mimic bees. These flowers trick the male bees into attempted copulation, and deposit a pollen packet on to the presumably frustrated male. The bee goes on and if it makes the same mistake, it pollinates the next flower that fools it again (do they ever learn?).

This is not stark beauty like desert or tundra. It is diversity in your face with life evolved to use every nook and cranny. You cannot see far in the jungle, but there is lots to see right in front of you. There is something new for the observant biologist at every turn. If you sit still in one place in the jungle, the diversity will come to you. A mixed feeding flock of birds will eventually come foraging through the jungle. There are a half dozen species of birds in these flocks. Some eat bugs from the bottoms of leaves, others move up and down the trunks. Some of the species catch the insects that fly up when they are disturbed by the other birds. The birds receive benefits from feeding as a group; they are more likely to detect predators such as forest hawks, and their feeding habits complement each other.

Mixed feeding flocks are but one example of the co-evolution that is so common in the tropics. Species in this habitat are more likely than any other, with possible exception of coral reefs, to have evolved characteristic in response to the other species in the environment. Many species have complex adaptations to the others found in their environment.

The bull-horn acacia, Acacia cornigera, found on forest edges, is but one example. Ants protect trees and shrubs from grazers. If you hit the trunk of the shrub, the ants create a sharp smell which is the chemical (pheromone) that the ants use to signal each other that there is an invader. The ants swarm to attack any animal that tries to eat the tree. At night, the ants descend to clip back seedlings of other plants that might compete with the acacia. In return, the ants make their nest in large hollow thorns, and eat food bodies with fats and proteins, and nectar with carbohydrates produced by the plant. An acacia that has the ants removed is quickly consumed by the many herbivores found in the forest, including the ever-present leaf cutting ants. The ants and the acacias have evolved a tight cooperative (mutualistic) relationship in response to the benefits each can provide.

Many more examples of co-evolution exist. Toxic butterflies are brightly colored to advertise “don’t eat me”. Other species of butterflies have evolved color patterns that mimic the toxic butterflies so they are protected form predators. Every species of insect seems to have a specialized species of wasp that is parasitic upon it. This list of entangled interrelationships goes on and on and provides endless fascination for those interested in biology.