The Rainforest  

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 I don’t really think someone can truly call themselves a biologist unless they’ve been to a rainforest, a coral reef, and a desert.  The first two are explosions of life, living expositories of all manners of symbioses and behaviors.  The desert is stark in its simplicity, with each organism a textbook of adaptations to extreme conditions.

I’ve been to coral reefs and deserts, both early and later in my career.  Prior to coming to Costa Rica on this trip, I had been to a tropical rainforest for a very brief visit, and to temperate rainforests for some more extended exploration. La Selva was a chance to immerse myself again and more deeply in what is perhaps the most fantastic of all terrestrial ecosystems.

 We had flirted with the tropical rainforest earlier in the trip.  At Rincon de la Vieja we were certainly in a moist tropical forest, and the cloud forest at Monteverde is only one step removed from being a tropical rainforest.  But, for the most part the rainforest was the last unknown of our trip and I was really looking forward to it.

 We got to La Selva on Tuesday, May 24^th, after a long day of bus rides from La Fortuna. After being greeted, we headed across the suspension bridge over the Rio Puerto Viejo to the River Station where our rooms were.  The long suspension bridge had a noticeable swing to it, and on the other side we paused as several of the group had to change from sandals to shoes – shoes to be worn at all times due to the very real possibility of encountering venomous snakes along the trails.  Passing over another bridge and past a swamp we worked our way up to the River Station on a bluff overlooking Rio Puerto Viejo.

 We had just a short time to move into the rustic station before heading back down the trail to the dining hall for a barbeque-type supper and small celebration of the last night at La Selva for a group from the University of Georgia.  Afterwards, I left the celebration on my own to head back a little early and spend some time in the rainforest at night. It didn’t take long to make my first discovery; the leaves of a mimosa tree growing next to the suspension bridge had closed for the night – making them less vulnerable to herbivores and less likely to dry out (in a rainforest?).  I stopped by the blacklight board set up on the edge of the woods; nothing spectacular was there but the spiders were eating well.  Down the trail closer to the station the leafcutter ants were hard at work, and back at the station to pick up my camera I found a large cicada buzzing around the light.  This cicada was about the size of our dog-day cicadas (Tibicen sp.), but the yellowish green of our familiar species in Ohio was replaced by a bluish tint in the Costa Rican cicada. It called quite insistently and loudly whenever it was held.

 I chose to wander down by the swamp near the river station and look for and listen to the several species of frogs calling there.  On the way I stopped to peruse the bushes and the edge of the trail, always alert for the presence of fer-de-lances which are more nocturnal than diurnal.  I didn’t see any snakes, but I found a variety of nocturnal insects and their kin – strange caterpillars, spiders , grasshoppers, katydids and the like.  Near the swamp at night, the forest is alive with the sounds of frogs; as one moves from the swamp as I did returning to the station the sound of the frogs faded and the calls of the katydids and other orthopterans came to the fore. I was able to photograph a few of the frogs, and near the station a giant toad (Bufo marinus) was hunting under the lights.  I took a shower, warily watching the tarantula prowling the screen up near the ceiling; if nothing else I had learned on this trip to shower with my eyes open.  Although it was hot and humid, an electric fan in the room stirred the air in my room and I had a good sleep.

 I was up at dawn to walk the trails a bit more.  Working my way along the trail paralleling the river I was immediately confronted with the diversity of insects,  other animals and plants.  The katydids’ songs were less frequent now, replaced by a cacophony of bird songs filtering down from unseen singers high in the canopy.  Along with the birds were the piercing songs of the beautiful greenish blue cicadas that also inhabited the high treetops. Closer to the ground, a low raspy chirping came from the tiny blue-jean dart frogs  (Dendrobates pumilio), which seemed to stir a little after dawn and which occurred in patchy abundance through the forest for the rest of the day  (Frog Video!). These small frogs were about the size and color of a strawberry, except for the blue-clad hind legs.  I suppose if you are going to be poisonous (to eat), it makes sense to advertise it, and if you advertise it by color you probably ought to be active during the daytime when the predators can see your warning coloration.  Apparently they get the poison in their diet.  These fascinating frogs have another unique trait.  The females lay around four eggs; over the course of the next week the male will return to moisten the eggs daily.  When the eggs hatch after about a week the female will take the tadpoles on her back and place them individually in the water filled “tanks” of bromeliads up in the trees.  She returns periodically to lay additional unfertilized eggs in with these tadpoles; the eggs are food for the tadpoles.  

Returning from a typically hearty breakfast, I found that a large scorpion had been deposited in a wastebasket set outside my door, apparently having been taken from under one of the student’s beds.  Scorpions being old news by now, I snapped the obligatory photo before heading off to our first real activity, a guided tour of some of the trails.  But even such a mundane task is not accomplished without incident – on our walk to the nature walk we encountered a spectacularly large grasshopper [2]and a peccary [2].  And, on the way back over the bridge with our guide we ran into a particularly bold coati; eventually the coati moved through our group and traipsed across the bridge, causing the following group to move to the side of the bridge so it could pass.  

One of the first things we learned about La Selva is that at one time parts of it had been a cocoa plantation, with many cocoa trees still growing in the shadow of the forest.  The fruits are cauliflorous, which does not mean that they are foul-tasting white vegetables.  Rather, it means that the fruits (or, more accurately the flowers which gave rise to the fruits) grow directly from the stem.  This  provides a strong structure for the heavy pods to hang from. The flowers are pollinated by midges of the family Ceratopogonidae.  We saw a number of other adaptations of plants to the rainforest – drip tips [2], lianas (vines), a variety of fruits, epiphytes, and so on, as well as a number of insects. We saw several different species of ants, including one that built its nests on the underside of Heliconia leaves, as well as the infamous bullet or bola ants.  Supposedly, the sting from one of these ants is the same as being struck by a bullet, which begs the question of how many people have both been shot and stung by these ants!

I also had the opportunity to look at termites by breaking through one of the covered walkways they construct between there arboreal nests and the ground.  Most of the termites which come out after such damage is done are soldiers, and in this case they were nasutes, a special type of soldier that exudes glue from its enlarged head with a single snout.  This glue, combined with various chemical irritants, is able to repel even large invaders such as anteaters.  

Perhaps one of the most amazing sights of the day was the helicopter damselfly click to activate this link -->(Megaloprepus coeruletus)  <-- click to activate this link, which we saw near the arboretum.  These damselflies, the largest Odonata in the world, have a wingspan of 190 mm and the abdomen itself is about 100mm long.  Unfortunately, they were flying high and I was unable to photograph them. The link here takes you to a picture taken by my friend Dennis Paulson, who helped me identify some of the other odonata (and other organisms) I saw in Costa Rica.  Thanks, Dennis!

In the afternoon, I went for a long walk accompanied by Alicia Burtner.  We saw more of the dart frogs, and eventually came out by the successional plots where the forest had been cleared and allowed to regrow for certain periods of time.  We eventually reached the end of the property and turned back.  Alicia headed back to the station and I continued down a side path, which turned out to be a lucky thing, since I encountered a class observing a group of Spider Monkeys (Ateles geoffroyi). This was the 3^rd species of monkey (click here for monkey page) that any of us had seen on the trip, and I was the only one to see them.  The viewing wasn’t very good, however, and I moved on, only to encounter them later near the end of my hike on the upper swamp trail near the River Station.  Here they came quite close, and I was able to get a few good shots even in the low light. The monkeys seemed to be keying on me, and one in particular came out in the open to keep an eye on me, or so it seemed.  I seemed to be disturbing them a good bit, so I moved off.

The dead gaudy leaf frog was still where it had been in the morning.  I turned it over to find several maggots on the underside.  Nearby, I found a live frog of the same species, but dull grayish-green with closed yellow eyes as it slept exposed on the upper surface of a leaf.  I later found that these frogs shed most of their bright colors as they sleep the day away, and that they will play dead when disturbed.

I again returned to the swamp, but with the video camera rather than the digital still camera to record the sound of the frogs at the pond.  Despite the early sunset these days are long – you can actually see more at night than during the day (at least in terms of animals) and it’s hard to go to bed.

 Thursday morning at dawn the Chestnut-mandibled Toucan was back in the tree outside the River Station, but this time it was joined by another toucan species, the Collared Aracari, (Pteroglossa torquatus), and we were off to another day.  The morning walk revealed few new surprises, and I took the opportunity to use a wide angle lens to record the forest instead of the trees.  Breakfast was omelets, buns, fruits, and, of course, beans and rice.  We spent the morning at the banana plantation Finca Zurqui, and returned to a free afternoon.  I once again set off in pursuit of the helicopter damselflies.

 Of course, I had no luck, although I was able to photograph a number of other damselflies, as well as a profusion of insects, and the great masses of tadpoles in the swamp.  They were dense and clustered, almost moving as an individual organism.  Does such a large mass scare away or fool predators looking for a small snack?  Or does it simply defeat the predator who strikes expecting to find a solid catfish rather than a gaggle of tadpoles?  

By mid-afternoon it was too hot to keep working in the forest and I turned my attention to the aquatic realm.  Several of the students were attempting to moor a flotilla of innertubes in the Rio Puerto Viejo at the foot of the river station.  David Brown and I worked our way downstream a kilometer or so, investigating the banks (and me trying to photograph an elusive damselfly). There was a large spider along the bank, as well as a variety of liverworts. We found butterflies that were puddling on the far bank, and soon discovered what drew them to that location – it was apparent that cattle visited the area and the butterflies were drinking up the nitrogen-rich groundwater where the cattle had relieved themselves.  We eased back into the water, now being a bit more careful about swallowing it, and floated back downstream to the station; one of the cattle came by to see us off.

David and I then split up; he went with one of the station staff to see where we would be doing the transect the next day; I took the students to the arboretum where we located several leafcutter ant colonies for our work that night.  Unfortunately, none of the colonies seemed to be feeding on any of the identified trees, making our project a bit more difficult.  On the way there, however, we crossed a small stream where a dead fer-de-lance snake was snagged in the current.  A flotilla of bass-like fish were dashing in to rip off hunks of snakeflesh, retreating only when the large turtles there moved in for their turns.

 After dinner it was back to the swamp as usual, but this time we found some gaudy leaf frogs .  We had other plans for the evening, but their presence encouraged us to return when our tasks were complete. We went on to the classroom to watch a few videotapes.  One was by click to activate link->  John Acorn <-click to activate link, an acquaintance and correspondent on the Odonata listserve.  The second was from National Geographic; both had been filmed in part at La Selva.  During the National Geographic tape an amazing thing happened.  I was sitting by the open window, with the sounds of the forest entering my left ear and the sounds of the video coming from my right.  The sounds were synchronized; the real world sounded exactly like the tape, with the same mix of insects calling.

 Our main task came next, recording the foraging of leafcutter ants.  Rather than hike back to the arboretum, we decided to simply work with a well established colony with trails running through the lawn of the station.  Most of the foraging was taking place on a single tree, but we soon realized that the abundance of epiphytes on the tree would make any simple identification of the leaf fragments impossible.  We contented ourselves with counting the number of fragments gathered over a several minute period, and collecting a hopefully random 100 pieces of leaf fragments that the worker ants were carrying.  Later dried and weighed, these would allow us to make a rough estimate of the average size of a leaf fragment, and this, coupled with our data on how many leaves were carried would allow us to estimate the amount of biomass the ants removed daily.

During this time we also spotted a few denizens of the night, including a particularly photogenic walking stick. Hard to find during the day, when they go to great lengths to resemble, well, a stick, they are active feeders at night.  It was also fun to shine a headlamp into the grass and see the many reflections from spider eyes.

Back at the swamp, we were lucky to find the Gaudy Leaf Frogs again, and this time we caught a pair in amplexus .  The male seemed completely oblivious to our presence, but the female began to oviposit on Josh’s hand.  They were immediately released to lay their eggs in a more suitable place.  On our way back up to the River Station we encountered army ants on a raid .  This was a different species than the one we had encountered at Santa Rosa; these army ants specialize in raiding the nests of other ants.  Still we were able to observe a number of army ant behaviors, including their building of "bridges" out of the bodies of the workers and soldiers.  There was also an ant mimic, a myrmecophile in the column. Myrmecophiles mimic the ants and live with them, some are parasitic while others are commensal. Finally, to cap off the night, a large cerambycid beetle was on the screen at the station. These beetles have larvae that live in wood and are also called long-horned beetles because of their long antennae.

Friday May 27th was transect day.  Having been up late the night before, I skipped the really early morning walk, but wildlife is everywhere at La Selva, whether it be a spider in the sink or an iguana in a tree at the way to breakfast.  After breakfast, I helped David Brown mark the lines we would be using for the transect later in the morning.

With the equipment ready, we set off for the transect site in the primary rainforest. As usual, the journey was as exciting as the destination.  We saw a lot of neat things along the trail including an impressive spider and a bullet ant that had captured a bee.  At the site, we unpacked the equipment and the students began to string the lines from which they would make their measurements of tree size, light, soil moisture and pH.  I paralleled the transect lines and used the opportunity to examine closely some of the life off the path; being an entomologist I naturally focused on the insects and other invertebrates.

What did I find?  A wasp that had turned the tables on a spider; now the hunter was the prey and the wasp was trying to figure out how to fly off with its paralyzed prey.  There was cockroach that was actually colorful, and perhaps the most beautiful butterfly of the trip, with wings like stained glass.    I also chanced upon an ant, probably an army ant soldier, that had apparently been felled by a fungus; the fungus, growing inside the ant had killed it and was beginning to emerge from its legs; a smaller ant was taking this scene in.

Ant lions prowl the forest floor, digging pits into which ants and other insects fall.  The ant lion larvae waits at the bottom of the pit to capture the prey.  We saw the pits at Santa Rosa, but no adults.  At La Selva I saw an adult ant lion, but no larvae.  Even more fascinating was a hagmoth caterpillar.  This caterpillar was well-camouflaged, looking like moss on the surface of a leaf. The hagmoth caterpillar is among the best mimics in the forest.  I also saw a darkling beetle; when I looked at the photos later on the computer I noticed it had a hitchhiker.  This is an example of phoresy; mites and small insects often hitch a ride on a larger insect.  Other organisms present on the forest floor included a small anole.

The transect itself went well.  The students were well-practiced from the earlier transect at Santa Rosa, and we had worked out a few tricks to make things go more efficiently.  The line was strung through the forest and the measurements were taken; the only real difficulty was the dense underbrush in a few places.  We were all glad that the mosquitoes were not as bad as we had feared; the heat and humidity were bad enough.  Gratuitous picture inserted here.

We dismissed the students at the transect site and we all began to walk back for lunch.  David Brown and I kept stopping to look at things, and soon wound up in the back of the group.  Here, as we were walking through the arboretum, David spotted a snake on the ground.  We followed it through the cleared forest floor of the arboretum.  It was dark green above with a bright yellow belly.  Later we would find out that it was a Bird-eating Snake, known more formally as Pseustes poecilonotus. The name is appropriate as several guides mention the fact that they eat birds.  It is a diurnal snake, so we weren't surprised to see it abroad in the daylight.  We were able to watch it for some time before leaving it to its hunting.

After the snake we passed a number of butterflies as we returned to the River Station.   Several of these I haven't been able to identify yet, but, again thanks to Dennis Paulson, I was able to get a handle on several others.  One of the prettiest was the Aglaura Olivewing (Nessaea aglaura).  We also saw several Owl Butterflies; one in particular was the Orgetorix Owl Butterfly (Catoblepia orgetorix).  We also saw the Merops Daggerwing, Marpesia merops.

Some of the most important organisms in the rainforest - or any forest for that matter, are among the least appreciated.  If it weren't for the fungi, however, dead organisms would never release their nutrients to the root mat for recycling into the trees and other plants. On our walk, we spotted a number of different types of fungi.  It will be a while before I get a chance to identify any of the various fruiting bodies and other fungal forms we found.  So, in the meantime, I've put some of the pictures of fungi here for you to look at.

I was hoping to get pictures of Odonata - Dragonflies and damselflies - at La Selva and I did manage to get a few, even if I missed the one I was really shooting for, the Helicopter Damsel, the largest odonate in the world in terms of length and wingspan.  I was able to photograph 3 species of damselflies at La Selva (and bear with me here, some of these things don't have common names.  In the family Coenagrionidae (the narrow-winged damselflies), I was able to photograph Acanthagrion speculum.  My favorite family is the broad-winged damselflies (Calopterygidae), and I was able to get one shot of a rubyspot, Hetaerina miniata, so named for the red spots at the base of the wings (somewhat hidden when the wings are folded).  The last species of damsel I saw was a spreadwing (family Lestidae), Lestes tikalus.  Among the dragonflies, there was one Clubtail (Gomphidae), Epigomphus armatus.  The remaining dragonflies were all in the family Libellulidae, which includes many groups of dragonflies including amberwings, skimmers, pennants and gliders, to name a few.  One of particular interest was the Narrow-winged Skimmer  Cannaphila insularis, I saw several individuals of this species at different ages.  This species is one which develops a waxy coating or pruinosity as it ages and matures; in this case it is a dull blue color, but other species such as our Common Whitetail may have a bright white pruinosity.  In the case of Cannaphila insularis, I saw both immature individuals just starting to turn blue, as well as mature individuals with the entire body blue and darker markings on the wings.  Another libellulid was Anatya normalis, which I also saw in several places.  Anatya normalis looked very similar to one of our Ohio species, the Eastern Pondhawk, with its white appendages.  Other dragons were more brightly colored, including the bright reds on the Carmine Skimmer (Orthemis discolor) and its relative Orthemis cultriformis. Two other Libellulids I saw at La Selva were Micrathyria atra and Uracis fastigiata.

Since this was our last afternoon at La Selva, I decided to take one last long daytime walk (still looking for those helicopter damsels). A lot of work was being done in plots around the station; the variety of work is quite striking. I was particularly impressed by all the work being done on the various species of flagflower. I also wanted to get some pictures of the shallow roots that are such an integral part of nutrient cycling in a tropical rainforest.

I suppose I should mention some of the other organisms I ran into on the trails; starting with the lizards.  Anoles were present everywhere, scurrying in the underbrush or on the tree trunks.  Many were tough to identify, but one I was able to pin down was the Slender Anole (Norops linifrons).  Whiptail lizards (Ameiva festiva) were common; the young have blue tails.  We saw basilisks at Caño Negro, but here at La Selva I was able to see Striped Basilisks (AKA Basiliscus vittatus), especially near streams.

Of course the most obvious wildlife were the insects and other invertebrates.  The large Pleasing Fungus Beetles (family Erotylidae) were easy to spot; as was this bright red beetle.  There were many, many spiders, including a brightly colored orb weaver.  I found some insect eggs glued to a tree; I have no idea what insect they came from, but I admired the precision with which they were laid.  I've already talked about the butterflies, but I also spotted this chrysalis under the railing on a bridge.  And there were mysteries, like this thing which might be a uropygid, but frankly I don't know.

There were a lot of birds at La Selva - the trouble was in trying to see them!  A thick canopy high overhead makes it hard to see birds there (and if you had wings why wouldn't you be high up in the trees?) and the birds on the ground were very cryptic.  It was even harder to get photographs of birds, and I only managed to get usable pictures of 5 species.   I've already mentioned oropendolas the collared aracari and  the chestnut-mandibled toucans; these all perched high in the trees right outside the River Station where the clearing allowed a glimpse of the treetops.  

Ironically, the bird I got closest to was the toughest to photograph.  Right outside the dining hall were several small trees about 10 feet tall.  They were covered with fruits, yellow berries going to blue, and there were a number of small birds flitting about in the trees feeding on the fruits.  Most attractive of these were the male Purple Honeycreepers (Cyanerpes caerulus).  Both males and females were in the trees, but the males, with their bold colors. were much more photogenic, although neither male nor female was easy to photograph in the dense vegetation. I have a lot of pictures of blurs; not many of birds.  They may like honey, but they don't really seem to creep!  Then there was the Rufous Motmot (Barypthengus ruficapillus) which was perched in a tree near the suspension bridge one day.  But aside from these brief glimpses, the avian fauna of the station was left mostly heard but not seen to me.  This shouldn't be so surprising; as an entomologist I tend to move around a bit and keep my eyes down near the ground more than the average birder would.

We had a bit better luck with bats, as a number of them perched right on the walls at the River Station.  The predominant species seemed to be the Long-nosed Bat (Rhynchonycteris naso), but I'm no bat expert.  I could tell, however, that these bats were socially conscious. 

I've talked a bit about life at the station - the food was excellent and the dining hall was spacious and cheerful.  Where else in the world can you see a toucan one minute and eat Froot Loops™ the next?  Outside of the dining hall there was a wide porch with comfortable chairs to relax and talk about the day's discoveries.  I've already shown you pictures of the River Station and the rooms there which were simple but comfortable.  The paths merit special mention; they are concrete in many places allowing you to get to and from dinner without dragging in a lot of mud (or causing a lot of erosion). In addition to the suspension bridge there are smaller bridges where paths cross major streams in the station.  I mentioned the classrooms already, but to my chagrin I realized that I returned without good pictures of the fine classroom buildings, the library and modern research labs that make up the core of the station.  You might want to click here to visit the La Selva website.   Now, I've been at field stations, such as Stone Lab in Ohio, and one of the most important features of any field station is a place for diversions.  At Stone Lab, that was the volleyball court, but in Costa Rica one of the most important  facilities at any institution is the football (that's soccer to us) field, and it was busy every afternoon.  I was amazed to see a lively game every day even in the 94 degree F heat.  One of our number, Jessie Kalus, had just finished 4 years playing soccer at Marietta and got a wistful look in her eye every time we passed a soccer field anywhere in Costa Rica.