Marshall Olson's Diary
Rainforest Caterpillars, Costa Rica
May 15-28, 2003


Tuesday, May 27, 2003
Monday, May 26, 2003
Sunday, May 25, 2003
Saturday, May 24, 2003
Friday, May 23, 2003
Wednesday, May 21, and
Thursday, May 22, 2003


Tuesday, May 20, 2003
Monday, May 19, 2003
Sunday, May 18, 2003
Saturday, May 17, 2003
Friday, May 16, 2003
Thursday, May 15, 2003

Related Sites

Tuesday, May 27, 2003

Today was sunny and warm. It was our last day at La Selva. Most of the team members took turns working at the banana zoo one last time. I meandered all around the encampment, taking pictures to try and emblazon the station into my memory. The tree sloth by the walking bridge was posing, and howler monkeys were howling. Three howlers crossed over the walking bridge by climbing along the cable.

While walking around, I tried to get a handle on what I enjoyed the most about this adventure. The opportunity to be part of serious scientific research that potentially could make a difference in our world was certainly appealing. It was also a bit like summer camp when you were a kid. You make friendships with a team that are quite intense for the time you’re together.

I particularly enjoyed talks that had an international flavor. We debated and discussed, all the while learning from each other’s experience and different points of view. But ultimately, it was the beauty and extraordinary richness of the rain forest that made the adventure one of the true great times of my life.

I wish to thank Alcoa for supporting something as important as the Earthwatch Institute in its quest to find solutions for a sustainable future. I personally am proud to be part of the first Earthwatch experience sponsored by Alcoa. Hopefully, many more Alcoans will have the opportunity to become Earthwatch participants in the future.

Monday, May 26, 2003

Spent the morning collecting caterpillars. In the afternoon, Lee gave us a final summary of our work over the last two weeks. We collected 300 caterpillars at La Selva. Over 700 caterpillars were collected from the banana plantations. We found 19 of the 30 families in the class of lepidoptera, including 82 species. To date, 33% of our specimens were parasitized. Two of the caterpillars were new species not collected here before. Lee now has 20,000-plus records to work with.

Lee compared the work at La Selva to work being done in a dry-land forest with deciduous trees in Costa Rica. Comparatively, many more caterpillars were found in the dry land. This is not too surprising. The trees around La Selva do not regularly lose their leaves. Some of the leaves are 10 years old or more. So not only are they tougher, the leaves are more toxic. Seen this way, the lowland rain forest is a more difficult place for caterpillars to survive than a higher dry-land forest.

Sunday, May 25, 2003

I went with Angela, a graduate student working for Lee, to a banana plantation to check on predation of pre-identified caterpillars. In this test, we were trying to check the amount of predation occurring in the plantations, particularly by parasitoids. Most were okay, but some were parasitized and dead.

Bananas are the number one fruit sold in the United States and around the world. Bananas are essentially wimpy plants, clones without so much as a woody stem. They are susceptible to all kinds of problems, not the least of which is caterpillar damage to leaves. Huge amounts of pesticides, fungicides, etc., are used to fend off enemies. There seems to be little regard for integrated pest management techniques. One notable exception occurred in Costa Rica. Parasitoids were killed by a pesticide meant to kill caterpillars. The number of caterpillars skyrocketed because their natural enemies were removed. After that discovery, spraying for caterpillars in most of Cost Rica ceased, and their numbers came down in correlation with an increase in parasitoids. The number of caterpillars we found in the plantations makes us wonder if now something else is killing off the parasitoids.

Saturday, May 24, 2003

Frank and I set out nectary bioassay samples on trees scouted out for bullet ant populations. It takes two people to do this. One person sets out the vials, and the other has to guard against attacking ants. If Frank hadn’t been vigilant, a bullet ant would have gotten me by climbing down the stick we used to brush them off the vials. We had to wait an hour before collecting the sample and replacing it with a new one. Surprisingly, no one got stung while doing the nectary work.

We rode bikes out to the remote lab to find our companions swimming in the river. We were told the piranhas in the river were the fruit-eating rather than the meat-eating kind, but it still was a bit unnerving.

It was incredibly hot and sunny, and we had a soccer tournament with some of the locals who work at La Selva. We won twice! The Europeans on our team saved the day. That evening, we all hiked to town where we had chicken and all the local fixings. While there, one of our teammates, Eduarda, got stung by a bullet ant!

Friday, May 23, 2003

Back to work at La Selva. It rained hard all day. Have I mentioned it was the rainy season? I worked the banana zoo, and it was a good thing because the folks who went out collecting came back drowned rats. We’ve collected over 500 caterpillars so far from the banana plantations, and we have to clean bags and add food daily. We also have to separate pupae and note dead caterpillars. We have begun to find parasitoids sprouting out of caterpillars like scenes from the movie Alien.

We attended a fascinating talk by Dr. Deborah Clark about tree canopy studies she’s been doing in partnership with her husband, Dr. David Clark. The Clark’s research, along with others, extends over the last 20 years. She started out with three lessons learned. Long-term biology research is the only way to go. Teams are advantageous over individuals. Results are often accidental discoveries.

Their work began by trying to understand why there is such diversity at La Selva, with its more than 330 tree species. Their research has evolved into understanding global change through observations in tropical forests. I found it interesting that even in the tropics, it takes trees 80 to 120 years to reach the upper canopy. One reason is the trees get broken. Another reason is there are huge growth differences from year to year. When carbon dioxide (CO2) is closely balanced with oxygen, growth slows. According to the Clarks, climate is the driver, and currently there is more CO2 in the atmosphere than any time in the last half million years. There is also an optimum temperature for growth. If it’s warmer than the optimum, photosynthesis is reduced and productivity lowers. The Clark’s data show strong decline in tree growth with increased temperatures. The data also suggest that the tropics are a key player in atmosphere makeup. Worldwide atmospheric gas samples and the La Selva tree data match. As Dr. Clark put it, “La Selva is a miner’s canary for global warming.”

Wednesday, May 21, and Thursday, May 22, 2003

Our team split into two groups. One group decided to stay and observe the volcano and explore the nearby rivers. Another group, of which I was a part, headed out to see the Caribbean and a national park along the coast.

After traveling through beautiful country and huge banana plantations, we stopped in Limon for lunch. Limon is a large harbor town that I’m sure is not a tourist destination. We weren’t sad to continue south to the park and pristine beaches. We observed lots of wildlife and met interesting people. The beaches had a distinctive Caribbean island feel. Luis from Madrid, Spain, made the language barrier non-existent.

Tuesday, May 20, 2003

Tom, Chris, Luis, and I went caterpillar hunting today. I ran into a mother lode and found 25. We also found a swimming hole and a couple of beautiful snakes (non-poisonous). The sky was blue with lots of sunshine and heat!!! The humidity had to be 100%. I have become a fan of rainy days.

The next two days were free days, and we all decided to visit a live volcano. We wanted to see the lava at night, so we headed out in a bus. As it turned out, it was too cloudy to see but we found a nice hot spring and enjoyed some rest and relaxation.

Monday, May 19, 2003

Parrots woke me today.

Several of us collected caterpillars all day. To qualify for capture, the caterpillars needed to be older than two instars (fairly large) since they’ve been around long enough to be parasitized. The exceptions were geometrids. Geometrids, or “inchworms,” were often tiny and specific to certain plants. I only found one. This was not unexpected, as we were collecting in primal old growth rain forest where the conditions for caterpillar survival are low. However, this was a good area to find rare or even undiscovered caterpillars. Lee purposely did not give us direction on how to look for caterpillars. He was hoping we might search in unique ways and consequently find something new.

We saw several exotic birds during our walk—toucans, a black turkey-like bird, something that looked like a guinea fowl, and many colorful songbirds. Some of our group went to a banana plantation and found gobs of caterpillars. This was unexpected and could signal a major problem developing. Others went to the remote lab to take care of the zoo and process new caterpillars.

In the afternoon, we did nectary work. We learned how to make two kinds of nectar—one made from sugar water and specific caterpillar extract and another, known as the “control” nectar, of just sugar water. In the field, one vial filled with the control nectar and one vial of the sugar water with caterpillar extract were hung in trees known to have bullet ant colonies. Bullet ants are large and very aggressive predators of caterpillars. They not only bite but sting with their abdomen like a bee does. The purpose of the experiment is to test for the presence of defensive chemicals in the caterpillars and their host plants. The results will be used to create a chemical variable for each caterpillar species and examine the effective chemical defenses against different parasitoids.

On a tip from Lee, I went to the “swamp” after dark to find what lurked out there. What I found in my flashlight’s glare as I waded in water up to the tops of my rubber boots was a surreal landscape of plants and water full of amazing frogs. There were frogs the size of softballs and other tiny ones in every color of the rainbow. The noise was deafening. Lee mentioned that after a heavy rain the frogs come out in huge numbers. He was right. I also found out my boots leak.

Sunday, May 18, 2003

Howler monkeys woke me up.

Collecting caterpillars most of the day was on the agenda following breakfast. The rain was incredible. I have quickly come to appreciate my rubber boots and umbrella since it’s too hot to wear rain gear.

I found four caterpillars. Vince, who I was with, landed 11. Some of the other volunteers processed and ran the zoo. After collecting, a group of us got together and had a soccer game. Being an international group, we had some great soccer players. I was not one of them. It started raining so hard the soccer field turned into a lake. It didn’t stop us from playing, though.

Saturday, May 17, 2003

Today we learned how to collect caterpillars. Insect damage was a big clue as to where to look. Other clues were folded shelters or rolled up leaves. I was surprised to observe almost all plants in the jungle had some type of damage.

We learned to “process” caterpillars by poking them gently to test what type of defense mechanisms, if any, that they used. These included thrashing, vomiting, and dropping from their perch to avoid potential predators. We also noted whether they were apsomatic (color defense) or cryptic (blending in) and if they had hair or spines. After testing, we would collect samples of the host plant in a plastic bag along with the caterpillar.

We next learned how to take care of the caterpillars we captured. At the “zoo,” we cleaned the bags of frass (caterpillar feces) and added new leaves for food. We were to observe the caterpillars to see if they threw their frass—another defense mechanism to make it more difficult for parasitoids to find them. Parasitoids key in on frass to locate caterpillars. We also examined the bags for internal enemies. Wasps or flies might have laid eggs that are growing inside the caterpillar. If a caterpillar made it to adulthood, we would record the date and kind of butterfly or moth that emerged.

Lee gave another evening talk on the caterpillar project and the tri-trophic interactions (nutritional requirements of specific plants, caterpillars, and parasitoids) at work. He started out with a question. Do caterpillars that have specialized eating habits (eat only a single species of plant and even parts of plants) have an advantage over generalists (caterpillars that eat a variety of plants)?

Scientists Paul Erlich and Peter Raven discuss this in their paper Butterflies and Plants: A Study in Co-evolution. They argue that the host-plant associations we see today have been shaped by a co-evolutionary process in which plants evolve defenses against natural enemies. The enemies, in turn, evolve new capacities to cope with these defenses. In some cases, caterpillars use sequestration—avoiding predation by using chemicals in plants. If this hypothesis is true, it appears that specialist caterpillars have the advantage over generalists.

In addition to the host plant-caterpillar co-evolution, there is another ongoing interaction. Some parasitoids (parasites that kill their hosts) are natural enemies of caterpillars. Caterpillars also must develop prey defensive characteristics. The defense mechanisms we test for during processing are examples of these characteristics.

Friday, May 16, 2003

We left San Jose for La Selva this morning, and it again was raining. We couldn’t see much on the two-hour ride to the rain forest, but we were definitely dropping in elevation. San Jose was in the mountains, and we were heading to the lowlands. When we arrived at La Selva Biological Station, it was sunny, very hot, and humid. It would take some getting used to, but the beauty was breathtaking. It seemed like every exotic houseplant I knew of grew wild here. We hiked with our gear across a walking bridge, and a half-kilometer (third-mile) later we found our barracks at the river station. Our rooms were simple with shared bathrooms, but they were much nicer than I was expecting.

After getting situated, we went to the cafeteria for lunch. We then went over the layout of the research station and received some safety advice. We were told to always have a flashlight handy. In the jungle, it goes from light to dark with little warning. The vegetation blankets the sunset and turns the night very black. Wear rubber boots. Unless lounging at the barracks or cafeteria, boots are a good idea as stealth vipers are numerous and virtually invisible. These poisonous snakes, we were told, sit in one place for days, even weeks, and then strike when something warm (like a rodent or sandaled foot) walks by. The other item to keep near was an umbrella. Lee Dyer then proceeded with an overview of La Selva and a lecture on caterpillar taxonomy.

Lepidoptera (butterflies and moths) go through a complete cellular overhaul. Metamorphosis occurs as they molt. These molts are called instars, and the average number of instars is five. Sometimes amazing changes occur.

Caterpillars have free-living embryos in their bodies. During the final pupae molt, all of the larval cells die. The free-living embryos grow into adult cells, thus completing the metamorphosis.

Caterpillars have well-defined heads, six eyes, and their salivary glands often make silk. The thorax has six legs, sphericals (breathing apparatus) and three segments. The abdomen contains 10 segments. The segments sometimes have prolegs covered with crochets, which we were told is where the idea for Velcro came from.

Thursday, May 15, 2003

Arrived in San Jose. I explored the city and, as in many of the days to come, it was raining. The Earthwatch team began to show up at our rendezvous location. The 12 team members came from England, France, Spain, Malta, and different parts of the United States. Over dinner at a very good Italian restaurant, Lee Dyer, project investigator, along with his assistant, Angela, gave us an overview of how the next two weeks were going to proceed.


Related Sites


Rainforests

Take a Walk in the Rainforest
A self-guided tour of the Costa Rican rain forest by journalists at the Public Broadcasting Service (PBS).
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Caterpillars

The Biology of Caterpillars
From World Book Encyclopedia.
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FAQs about Caterpillars
Twenty-two frequently asked questions are answered by two Australian educators.
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Photographs of Caterpillars
Twenty-six beautiful color photographs of different species.
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What's This Caterpillar?
An online search engine to help you identify 800 different caterpillars in Europe.
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Factoids about Caterpillars, Moths, and Butterflies
Thirty-two factoids to ponder.
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Earthwatch Institute


Learn more about this international nonprofit, which supports scientific field research worldwide.
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Rainforest Caterpillars Expedition


Learn more about the expedition and its scientists.
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Costa Rican Caterpillars


A Teacher Scholastic discussion about Earthwatch's La Selva caterpillar field site and biological reserve.
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Caterpillars of Costa Rica


Facts and photos about caterpillars in Costa Rica and in other countries.
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Caterpillars & Parasitoids of a Costa Rican Tropical Wet Forest


An ongoing project to inventory and disseminate information on lepidopteron larvae, their host plants, and their parasitoids.
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Butterflies


Explore the butterflies of Central America.
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