Science Talk

Panamania!: A Visit to the Smithsonian Tropical Research Institute

We take a walking tour of the Smithsonian Tropical Research Institute on Barro Colorado Island in Panama, with the STRI's Beth King and Harilaos Lessios. Plus, we'll test your knowledge of some recent science in the news. Web Sites related to this episode include

We take a walking tour of the Smithsonian Tropical Research Institute on Barro Colorado Island in Panama, with the STRI's Beth King and Harilaos Lessios. Plus, we'll test your knowledge of some recent science in the news. Web sites related to this episode include

Podcast Transcription

Steve: Welcome to Science Talk, the weekly Podcast of Scientific American posted on June 17th, 2009. I'm Steve Mirsky. This week we'll go for a hike in Panama, plus we'll test your knowledge about some recent science in the news. Back in March, I and a few other speakers on our latest Scientific American cruise got to take a walking tour of the Smithsonian Tropical Research Institute, which is on Barro Colorado Island in the middle of the 85-square-mile Gatun Lake, which was created, when they built the Panama Canal. You'll mostly hear me talking to Beth King, the Institute Science Interpreter. You'll also hear the voice of staff scientist Harilaos Lessios and some questions from a few of the other folks on the tour. If we sound out of breath at any point, it's because I edited out the portions where we just finished climbing many hundreds of steps and then later steep trails. So here we go on a tour of the Smithsonian Tropical Research Institute, or S-T-R-I, or STRI, with Beth King.

King: So, I think our plan is to head into the forest, and we're going to go on one of the main research highways that goes through this outdoor laboratory and ends up at the area of this permanent study site.

Steve: When you say highway, what do you actually mean?

King: I say that because there's this trail system all around the island, but there are some trails that are used much more by others because they're going out to work and coming back.

Steve: Right. So we're entering the highway and it's about three feet across, but it is paved for now anyway and it's pretty dense, [a] lot of ground litter.

King: Yeah, so this is the end of the dry season, that's why you see so much ground litter; because the winds are strong, the trade winds are blowing down from the north and that's pushed the inter-tropical convergent zone away from Panama, which means it's not raining very much. And a lot of trees that produce seeds are producing them now so they can be dispersed by the wind. And the weather is beautiful.

Steve: It's pretty hot and steamy, although it's cooler here under the canopy than out in the direct sun.

King: So, we're coming down to a bridge over one of the streams. Oops! There goes a lizard; it's a little Anole lizard. So, we're actually standing on a bridge, and it's actually a little bit unusual to see this much water in the stream at this time of year because there's no source of water on Barro Colorado, so all of the water that you see is from runoff, and I was saying this is the end of the dry season. There are two main seasons in Panama: the rainy season from April to December and the dry season from December through April. And sometimes it doesn't rain at all, but this year it seems to be a rainy-dry season. It rains about 4 meters per year on the Colón side of the isthmus, about 1.5 meters per year [on] the Panama City side, and here in the middle about 2.6 meters per year. So as I said, when we're coming in on the boat, there're sort of two different kinds or groups of people who work on BCI: people who stay for a long time, they do their thesis or something, and people who might come for a course; so we have two different kinds of houses that you'll see. There're 64 beds total, usually about 45 or so full on any given day and these are sort of more dormitory-style rooms for people who are staying for [a] short time. And then as we walk up the hill, we'll see some of the houses for people who want to stay longer. Some of the houses have little kitchens and other amenities.

Steve: These dorm rooms are not air-conditioned.

King: No!

Steve: How's that?

King: So, this was the first laboratory building; it was built in parts. It was initially built in 1923, but at that time, it was just the upstairs and there are pictures of people sleeping and doing their lab work upstairs and this downstairs was closed up a few years later after that. And for a long time it was the dining hall and the dormitory and the laboratory, and this is a rite of passage. There are about 194 steps that come from the lake up to this laboratory, and so if you talk to the old timers from Barro Colorado, they tell you about arriving at the island and marching up the steps of the laboratory building. Stanley Rand who was a herpetologist here for many years used to say that this was the site of the longest ongoing cocktail conversation about tropical biology.

Voice 1: I have a really basic question: So is this technically a rain forest?

King: Technically, this is a seasonally dry, humid tropical forest. So some people will, sticklers will probably say that rain forest is not applied because it doesn't rain enough year around. Here you can see Soberania National Park, which goes along the whole eastern shore of the canal. It's about 18,000 hectares and up at the top of this, right along the ridge, is where the Transisthmian highway goes from Panama City to Colón, and so that's the, sort of the, border of that protected area and a lot of people are making the argument that that trees are essential for the canal operations because if it's deforested, there'll be erosion into the canal and that part of our experiment—to look at these different reforestation of native species and reforestation with teak and natural forest—is to put some numbers on those assumptions.

Steve: In addition to the erosion, don't you need the natural ecosystem to act as a water shed to hold all that freshwater that you need to keep pumping in and out of the canal?

King: Right. So people think that the trees also affect the rate of the flow of water and so the roots act as a sponge during these really heavy rains so that the canal won't be damaged by, you know, huge runoff from the area. But because the canal infrastructure, I guess, could be threatened if there's too much rain that comes off the area too fast, and then in times of drought, which are infrequent but do occur, then one assumption is that the sponge continues to hold the water, and there'll be continued runoff into the canal during periods of drought; whereas grasslands and other open areas tend to lose all their moisture very quickly. But those assumptions actually haven't been carefully tested, so this experiment that we're doing is looking at those, putting numbers on those assumptions.

Voice 2: Are these towers used for tracking the animals?

King: No, this one is a microwave tower, as we have a T1 connection, and so we have high-speed Internet on the island, they are microwave and then that one is a cell phone tower. And I like to tell people that, when I first came here in 1992, there were two phone lines on the island and the one of the residents wrote a poem that said the line to heaven is always occupied because his girlfriend was living in the island, and you could never get a call through. And now people call me on my cell phone in the office and while we're walking on the trail.

Steve: Right.

King: There's also a Web cam up there somewhere; I don't know if that it's working but ... And so this was the original laboratory area, and when I first came in 1992, that area right there was a big wooden lab, and that's where we did all of our work. But then the new labs that you saw down below were built in about 1996, and so a lot's changed here in the last 20 years or so.

Lessios: Well, the major change is the production of air conditioning in the laboratories, the [intention is not to mitigate] the temperature [but] the humidity. I mean, before that, anything you owned here will be overgrown by fungus—your shoes, your boots everything. So now they can do things; before they just couldn't keep certain instruments here and so the physiologists came in.

King: This is the weather station, which also is one of the sites of long-term weather data from the tropics; I guess [it] probably goes back to the 20th, so...

Voice 1: So you're collecting rainfall data there, I guess?

King: Yeah, this collects rainfall, humidity, wind speed, temperature and the shade temperature in the sun.

Voice 1: Those nests are of birds or are those some of the...

King: Yeah, those are the Oropendola nests; they're black with kind of yellow rumps. We heard one calling down there; it has a very melodious kind of lublulublu call. Oropendola. Yeah, so as to avoid the leaf cutter [ant] damage...

Lessios: There're moats.

King: ... there are little moats around all the greenhouses. And that little foamy thing in the corner of the moat is the nest of the túngara frog; so as the female extrudes her egg, she breaths this gel into a foam and her eggs are in the foam and that's supposed to distract predator[s]; but it's fun to look in at those moats because there're sometimes frogs and other things there, and you can hear the cicadas, too, in the background.

Voice 1: This is [not a nature] sound, right?

King: Yes, that's [a nature] sound

Voice 1: It sounds like a ...

King: And then in the dry season, it can get very intense and you can be working out in the field and it feels like ...

Steve: Yeah.

King: Ah!!! I have to hold my ears.


Steve: That is not the whine of some piece of machinery though, those are the cicadas.

King: Yeah, those are the cicadas.

Steve: Far more staircases than I expected in the forest.

King: Well, we're actually close to the lab. We've tried some different experiments to see what works best for visitors in terms of trail, but you'll see soon that the standard on the island are cement blocks that are anchored with iron rebar because they don't get slippery, and they don't erode in the rainy season.

Steve: Right, because these are a little bit slippery even now.

King: Yeah, these are wooden logs.

Steve: And in the rainy season, they'd be pretty treacherous.

King: Exactly. So most people like the cement blocks, except for a couple of really tall people, who feel like the gap between the blocks ...

Steve: The rise.

King: The rise, isn't ...

Steve: High enough.

King: And this is the water treatment facility. So, usually we have really great clean water on the island, but lately the canal is doing this expansion and one of the ways that they've decided to expand is to make the canal channel deeper. So they've been doing a lot of dredging, and I think we're still working on figuring out a pumping system that can deal with a lot of excess sediment for filtering. This is a Kapok tree, [the] famous, Kapok tree, but it's a baby.

Steve: It's a baby—how old is it?

King: Oh! It's probably 20 years old or something.

Steve: Still a good, what, 120 feet high?

King: Probably ...

Steve: Yeah.

King: It's hard to tell the age of tropical trees because they don't have rings and so sometimes there are little trees that are only about 2 cm around which have been sitting in the forest for years and just haven't had a chance to grow. And actually some of those are marked with tags, so you can actually know that this 2 centimeters tree has been 2 centimeters in diameter for the last 25 years, whereas the same species, another sapling that's a couple of yards away in the sun, is a huge tree and we know that they're from the same parent or the same ...

Steve: So, there's your nurture versus nature—[a] little sunshine.

King: Mmmhmm.

Steve: And fungus?

King: This is a big spider.

Voice1: Oh my God!

King: There are actually two spiders there. You can see the female in the center; she is large.

Steve: Male above.

King: And the male above, he's small. So the female is about 3 inches long and the male is about half an inch long or something.

Voice1: It's windy at this time, right? In August it's going be much hotter much more humid?

King: The temperature doesn't change very much, but it's supposed to be dry right now. It's a little more humid than usual [for] this time of the year; and then in by August it would be raining every day.

Voice1: [It just gets] more and more, okay.

King: Yeah, and then by November it rains all day everyday.

Steve: What are we collecting in this basket?

King: This is one of those long-term studies of tree behavior. So every week, there's a guy named Osvaldo who goes around and collects all of the leaf litter that are in these big mesh baskets, puts them in a bag and takes them back to the lab and identifies every little piece. And he identifies the leaves, the flowers, the fruit, and then they can compare that to the temperature and rainfall data and see, for example, if it's a wet-dry season like this year, how that changes what's in the basket, which tells you things about how the trees are responding to long-term or short-term climate changes. And one of the interesting things that they found is that there are many more liana leaves than there used to be, and there's this idea that there seemed to be more vines growing in tropical forests than there were. This was shown in the Amazon, and it was shown again here in Barro Colorado Island and no one is sure what that means. It could be that vines don't have to produce so much trunk, so they're responding more quickly to increased carbon in the atmosphere; or it could be some successional thing like that vines are just doing better at this time in history. This flower that looks like a shaving brush is the flower of a tree that's called the beer belly tree in Panama—the [barrigon, which means the big belly.] And it's a white flower because its pollinated by bats that can find them at night. And that's the tree over there, this big tree and you can see that it has a sort of rounded beer belly shape when it grows out into field that's something gets much more of a beer belly look and it also has stretch marks. We think there are about 1,200 howler monkeys on the island and the way we know that is every once in a while Katie Milton from Berkeley comes, and she sends people out to the tips of the island at dawn and at the dawn the monkeys tend to howl in their groups to kind of attract each other back, you know, as they come from their sleeping roosts. And so all of the volunteers record the number of monkey troops that they hear and then each troop contain usually around 20 individuals. I guess they got about 60 troops times 20 is 1,200.

Voice1: Over here.

King: This is sign of the howler monkeys, it's a dung beetle. The dung beetles come to the howler monkey dung and they form little balls of it, and then they bury it. Females bury the balls under the surface and they lay their eggs in the dung. It was actually a guy from Princeton who did this thesis about dung quality and how it affects beetle horn formation. Because apparently the larvae that have good dung as they grow, tend to be males that have these big horns, whereas larvae that have poor-quality dung tend to be small males that have big eyes and no horns. So we have five species of monkeys on the island: the spider monkeys, howler monkeys, white-faced capuchins, night monkey and mono titis which are the Geoffrey's tamarin. There is one group that looks at leaf chemicals, and we tease them, we call them trail biologists since they mostly work along the trails and they measure the amount of leaf damage in leaves and also the age of leaves. So, they can look at leaf defense.

Steve: And you tease them because they never go off the trail.

King: Yeah, once, they had a birthday party for a leaf that was 12-years old that they had found like every year for the last 12 years. I always tell people that: Don't pick the leaves, because the[y]re might be someone's 12-year-old research leaf.

Steve: Research project.

King: So, one of the reasons why we got these canopy cranes is you don't often get to see what's up in the top of the canopy where most of the action is. And here you can see a big branch of flowers that's fallen down.

Steve: From the top of the canopy...

King: From the top of the canopy, but actually before I was saying that there seems to be a lot of extra growth of vines, and one of the problems is that most of these vines are living and flowering way up in the canopy, and so people haven't even been able to identify them before. So now they are making a concerted effort to study vines, but it's interesting to see when things fall down. Also basically this whole slope that we are walking up now was probably mostly deforested during the canal construction. We found bottles of, we can still find bottles of beers and some things like that, and other evidence that people were here. And we also find trees that usually grow in open habitat, like the one here. And all of this jungle that you're seeing has all grown up in the last 80 years or 90 years. Well I smell some howler monkey; you get that stable-like smell?

Steve: What did you refer to it as?

King: Stable-like smell.

Steve: Oh, stable-like smell. No, everything smells kind of fresh to me. I am from New York, so...

Lessios: Further down this rail is this 50 by 50, I mean 50-hectare plot that's being monitored for the survivorship of every tree. So they don't like visitors to get in there and break things, but we can come to...

King: Visitors can see the edge.

Lessios: Yeah, they can come in there.

King: It's kind of cool just to see that they have actually tagged 250,000 trees, so I think something like 400,000 trees over a time considering the ones that have died and in the meantime and it's just amazing. So here you can see a big tip-up; these are famous because for a long time people thought that tropical trees all have very shallow roots, and most of them do. But we have also found that some tropical trees have tap roots and do get down to water that's more...

Steve: It's a leaf cutter, [it's] a leaf-cutter ant moving a leaf—there's one little branch about a thumb's width across there.

Lessios: Yeah, there, it's around the edge of the leaf.

Steve: Yeah, on the other side of the leaf, now it's going down that way.

King: Usually there's a lot, but I think it must have been raining enough this morning that they are not working; and there is one of those vines.

Steve: Ah... yeah.

King: That's (unclear 21:12).

Voice 2:

King: Also [talk about] monkey-ladders and things like that. Yeah, so sometimes people do like trapping in order to put radio collars on the animals, and then there are some other traps that are more permanent that are used every year to look at how [the] animal population is doing.

Steve: It's an authentic scary jungle sound.

King: So, this tower is actually one of about eight towers that are catching radio signals. So researchers catch the animal, they put on a radio collar or tag and then the towers records the signals; all the signals are all beamed back, basically, and then there is a triangulation so that then you can guess, more or less, where the animal is based on the signal strength. You know, they can probably know where every animal is at all times and what's it's doing; like, they can measure heart rate.

Voice 2: Wow, it gives you heart rate?

King: Yeah, and they can even put a microphone on [the animal] so they hear it munching or interacting. [But] some people were joking that, you know, it's [so] people know if they're graduate students are working or if they are staying in the dorm all day.

Steve: That's what the collars are really for.

King: But they can put transmitters on bees and seeds. I mean the transmitters have got pretty small, they don't always work well, so a lot of people, the researchers can be a little bit defensive, too; and people say, "Oh, you just sit in your lab and watch your animals on the Internet; you don't have to go out in the field." But actually most of what they have been doing here is testing these systems. So they do a lot of running around and hand tracking to see whether the animals are really where the system says they are.

Steve: So that they can make fun of the next generation of researchers who really can just sit in their labs.

King: Right. It was based on a system that was set up called "where is my bus", in which buses had transmitters. And they beam the radio signal back to the station and then you can see, if you could look on the Internet and see if your bus is going to arrive at the stop near your house. Well, apparently it's pretty common technology now in cities; that like courier services have transmitters on their fleet so that they know where their messengers are. This place is a great place to work because there are so many projects going on all the time. It's fascinating; it's a bit overwhelming.

Steve: Approximately how many discrete research projects are going on?

King: Well, we have 35 permanent staff scientists and we have, last year we had about 1,200 visiting scientists.

Steve: Well.

King: So some of those are student groups that may be 10 people at a time or something that. There are also ongoing projects; maybe the researchers don't come every year, so it would be hard to guess, but it's probably in the thousands somehow.


Now its time to play TOTALL....... Y BOGUS. Here are four science stories; only three are true. See if you know which story is TOTALL....... Y BOGUS.

Story number 1: Rhode Island's legislature has issued a formal declaration demanding that floating chunks of Antarctic ice stop being referred to as "the size of Rhode Island."

Story number 2: Nokia is working on a way to wirelessly charge cell phones via ambient radio waves.

Story number 3: The factor that limits the weight of flying birds is how fast they can molt their flight feathers.

And story number 4: Road crews working on construction for the 2012 Olympics uncovered a site with dozens of severed skulls dating back to the Roman occupation of Britain.

Time is up.

Story number 4 is true. Archaeologists are trying to figure out just whose skulls were unearthed in the road-building effort; early theories include them being the remains of native Britons defending against an invasion almost 2,000 years ago.

Story number 3 is true. The feather-molt turnover time is what apparently limits the overall size of a bird. That research appeared in the Journal Public Library of Science Biology. Big birds' feathers grow too slowly for them to molt fast enough to avoid long periods of flightlessness. For more, check out the June 17th episode of the daily SciAm podcast, 60-Second Science.

And story number 2 is true. Tech Review reports that Nokia is working on using ambient radio waves, which were bathed in to charge up your cell phone. They are also looking at embedding solar cells in devices.

All of which means that story number 1, about Rhode Island trying to get people to stop calling large ice shelves "the size of Rhode Island" is TOTALL....... Y BOGUS. But what is true is that the Rhode Island legislature just made it's the first state to expand existing medical marijuana policy to allow for state-licensed distribution centers. The governor had vetoed the bill, but the senate overrode the veto 35 to three, the house 68 to nothing. So it was a big joint effort.


Well that's it for this edition of Scientific American's Science Talk. Check out for the latest science news, and our photo feature called "Don't Lick That Toad'. For Science Talk, I'm Steve Mirsky. Thanks for clicking on us.

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