La Suerte - Marietta College

La Suerte Field Station

Costa Rica

Marietta College Biology and Environmental Science Department Field Trip 2005/2007

Note: Lots of big, pretty pictures on this page - it may take a while to load, even over a high-speed connection!

Above: Gecko, La Suerte Field Station

As you can see from the Google Earth image above, the La Suerte Field station is located in the northeastern part of Costa Rica about 30 km from the Caribbean. The native lowland tropical rainforest in the area has largely been cleared for agriculture, but some parts remain, and the station protects one parcel of that rainforest. The station sits about 50m above sea level and gets about 3.8 meters of rain per year.

The diagram to the right shows how elevation and location conspire to produce so much rainfall (both La Suerte and La Selva are in the lowland rainforest). The vertical scale is exaggerated at sea level, but basically what happens is this: much of the year the prevailing winds coming from the east bring moisture laden air from off the Caribbean over land. Here it rises and cools; as it cools the water condenses to form clouds and eventually rain. You can see this graphically in the Google Earth image above; look at the line of clouds that has formed just in from the coast - even before the air is forced up by the mountains. In this case the clouds are forming as air rises over the sun-warmed ground of the coastal region.

We went directly to La Suerte from San Jose in 2007 (it was not part of our 2005 trip). One of the station employees, Israel, met our bus in San Jose and traveled part of the way with us. Most of the trip was over paved roads, but near the station the area takes on a much more rural feel. We stopped in one town to purchase toldas for the whole group, then it was on past farms and banana plantations to the hamlet of LA Primavera and on past it to the field station.

Above - one of the rural bridges. Above right, the main building, with sleeping quarters on the 2nd and 3rd floors and the dining hall on the first floor. To the right, the cabins where the students stayed. A view of the bunkrooms is shown below; below right is the dining hall at mealtime.

Above: everyone cleans their own dishes after dinner; right, a dog that wandered into the field station while we were there.

It rained a good bit while we were at La Suerte. You don't mind it - or even notice it - too much when you are in the rainforest, but in the clearings it comes down very hard. All that rain means a lot of mud. Above, the class models the latest in rainforest footwear.

Left: Hiking in the rainforest. The station has a number of good trails; here the class stops in a light gap.

Below: The transect. A transect is a formalized way of gathering information about an area. You lay out a straight line on a compass bearing and take samples at regular or random intervals along it. We ran transects at La Selva and Santa Rosa in 2005 and La Suerte and Santa Rosa in 2007.

Below left: a line is snaked through the forest on a set compass bearing, with measurements taken at random intervals along the way.

Below right: We use a modified point-quadrant technique. At each random point along the main transect we construct an imaginary line perpendicular to the transect line and measure from the center point to the nearest tree in each of the 4 resulting quadrants. This gives us a feel for tree density. We also measure circumference of the trees 4 feet off the ground to give us a feel for tree size, age, distribution, etc.

Another big activity was studying the leafcutter ants (Atta cephalotes) at the field station. We did an extensive study of one nest, counting the number of ants and the number of leaves they were carrying. This, combined with some measurements we made at La Selva in 2005 allowed us to construct a number of exercises for students back at Marietta College. We also got some great video, particularly video of one soldier ant moving an incredible burden.

You can learn a lot more about leafcutter ants - and see the videos here:

Leafcutter Ants

There were other ants, of course. The image to the right shows two ants drinking sap from a broken plant stem; sap and nectar are important sugar sources for adult ants. Since the adults do not grow, their protein needs are minimal and all it takes to keep them going is sugar water. The insects, fungi, and other protein-rich material ants gather are used by the queen to produce eggs and by the growing larvae to reach adult size.

Below: The infamous Bullet Ant, whose sting purportedly feels like being shot by a gun; this comparison begs the question of how many people have experienced both.

Some of the students were about to let a bullet ant sting them on the arm to see how much it hurt; our guide, however, convinced them that having their arm basically useless for two weeks wasn't really a good idea.

There were a lot of birds at the field station. I have yet to identify the bird above; I took a lot of pictures of it though since it was a) close, b) carrying a katydid, and c) injured in some way on its chest.

The decal was on the side of the station truck. Loosely translated it says: "Don't buy young birds - they are stolen from their nests". This references the alarming trade in young birds from the rainforest to meet the demand for pet birds in the US and elsewhere.

To the left: A Pale-billed Woodpecker (which looks a lot like a Pileated Woodpecker). Below left: The Montezuma Oropendola, easily identified by its yellow tail and characteristic nests (see the La Fortuna and Arenal pages for views of the nests). Below a Blue-gray Tanager perched just outside the dining hall.

On our first hike into the rainforest our guide pointed out a pair of Mottled Owls that none of us would have ever seen. It was a bit of a challenge to get a good photo of them in the gloom of the rainforest.

Like owls elsewhere, these birds prey on smaller animals at night. I would love to get some owl pellets from the tropics to see what all they eat! Certainly there are more things creeping about in a rainforest at night than you would find in a temperate forest.

This pineapple was one of the ornamentals planted by the main station building.

We saw stingless bees just about everywhere we went in Costa Rica. These bees build a hive in a cavity in a tree and then build a narrow tube leading into it. The strong wood of the tree keeps out most vertebrate honey thieves such as raccoons and coatis; the narrow tube means that insect predators will have to work their way down that long tube under constant attack from the stingless bees guarding the way (above right). Although they do not sting, they are able to regurgitate a noxious, sticky chemical that they rub on trespassers - and they can bite as well.

Spiders were also well-represented at La Suerte. The type to the left seems to occur all over Costa Rica.

Below: A brilliant black-spotted, yellow leaf beetle, possibly related to the 12-spotted cucumber beetle found in North America. Also, one of the many tropical cicadas. These are often smaller than the Tibicen species we see in Ohio, yet somehow louder....

Above: Some sort of pink-bellied littersnake that one of our guides found and caught for us. Even when a group is led by two biologists with a lot of field experience, a fair deal of it in the tropics, it is amazing what you won't see - and what a local with no formal training but a lot of familiarity with the area will find.

Above right: An anole I found all by myself!

Right: a large brown grasshopper that was crawling on the window screens at the station. Note that the only green part of the body is the cercus (lower right). Why this is I have no idea.

Below: We did see some army ants, but not the large foraging colonies we saw at Santa Rosa in 2005 or Monteverde in 2007.

There were a lot of amphibians at La Suerte. Above, a tree frog clinging to a leaf surface during the day, as tropical tree frogs are wont to do. Right: a ranid frog in a rainforest pool.

Below: The ubiquitous Marine (Giant) Toad. Introduced in many tropical areas to control insect pests, they have spread widely and are found in association with human habitations and other disturbed areas in the tropics. They will even eat dog or cat food set out for pets. At La Suerte, as at Santa Rosa and other places we saw them they came out at night to forage on insects attracted to porch lights.


	We didn't see many gaudy leaf frogs on this trip (as compared to La Selva in 2005). We did take one night hike to a swamp, but it was too early in the rainy season for the frogs to be actively breeding as they had been at La Selva. We did find this one asleep on a twig; of course all the flash photography woke him up and he hopped off.

These are amazing frogs. During the day they blend into the surface of the leaves on which they perch; at night they awake and unfold their long limbs and expose the bright colors their name implies.

While we didn't have much luck with Gaudy Leaf Frogs we were rewarded with the sight of Green and Black Poison Dart Frogs, a species we did not see on our 2005 trip. These frogs are brightly colored to warn predators of the toxins contained in their skins. With this protection they do not fear predators and are active during the day (diurnal). Note how the black stripes always conceal the eyes. This is important; if a predator were to attack it would want to know where the eyes were so that it could strike at a vital area (or at least know in which direction the frog was likely to hop). The pattern of these frogs makes it hard to tell which end is which.

Our old friends the Blue-Jeans Poison dart frogs were common at La Suerte, and we finally got a good (sorry Dave) picture of one with a tadpole on its back. The females lay the eggs in a nest on the ground; the male guards the nest until the eggs hatch into small tadpoles. Then the female backs into the tadpoles, one climbs up on her back (and holds on with a sucker-like mouth) as she crawls high up into the canopy. There she locates a bromeliad with water collected at its base (up to 10 gallons in some big bromeliads!). She backs in and feels for the vibrations of any tadpoles already there. Feeling none, she deposits the tadpole there. She will crawl back to the ground and then return to the bromeliad. When she backs in on her return trips the tadpole will vibrate wildly, signaling its mother that the tadpole is there, and she will respond by laying unfertilized eggs for the tadpole to eat (the tadpoles get algae and detritus in the bromeliads, but these are low in the protein the tadpoles need to grow).

Actually, there is another Dendrobates in Costa Rica that closely resembles the Blue Jeans frog; it is Dendrobates granuliferus, sometimes called the Green-Jeans frog, although apparently its color is somewhat variable. I'm not convinced that the specimen above is not D. granuliferus or a hybrid of D. ganuliferusxpumilio. Of course, D. granuliferus is known from the Pacific slope of Costa Rica, not the Atlantic, but organisms have been moved by humans before - especially around field stations. Any experts out there want to weigh in?

In addition to the frogs there were a number of other organisms out there trying to break up the green monotony of the rainforest. Heliconia plants (above) do their best with shades of orange and even pink.

The bright orange flowers to the left managed to attract a hummingbird, and even caterpillars get into the act. The slug caterpillar below is protected by stinging spines from any predators that might want to take advantage of its conspicuousness.

In 2005, we had gotten a single, fleeting glimpse of one of the many poisonous snakes in Costa Rica. A Fer-de-Lance dove off the trail one night was we were returning to the River Station. La Suerte was more open with its venomous reptiles. The first hike on the trails yielded a small Hog-nosed Pit Viper (below).

The Fer-de-Lance came next. As dr. Brown and I were returning to the main building from the student cabins he suddenly jumped - having almost stepped in front of a Fer-de-Lance on the side of the driveway. Of course, he did not have a camera, and although I has two, one was a small point-and-shoot and the other was my digital SLR. The latter, however, only had a 60mm macro lens on it. Both cameras required me to get uncomfortably close to the snake trying to keep as much of my body behind the camera as possible. The results were decent; I particularly like the view one gets of the heat-sensing pits on the face of the snake (look between the nostril and the eye, then down just a bit).

Here is that first venomous snake, the Hog-nosed Pit Viper (the Hog-nosed snake of North America isn't really poisonous). This little (less than 1 foot long) snake was curled in the leaf litter on the trail, about 1/2 the group including the guide had stepped right over it, before it bit one of the students and killed him. This had the welcome effect of letting the rest of us see the snake, however (at least once we rolled the body away).

Again, I had only the point-and-shoot camera and the 60mm macro lens (where is the 400mm telephoto when you need it?), a pattern that would continue with our next venomous encounter at Cahuita. On the other hand, I was able to get in close and get some nice shots; again the heat-sensing pit is very obvious in the picture below.

The snake wasn't actually a killer, I just put that in to wake you up. We've actually come back with most of the students we set out with.

Typical rainforest at La Suerte - note the buttress roots in these two pictures.

La Suerte has both primary (unlogged) and secondary rainforest; the secondary was cleared at one time but is now reverting to rainforest. Other agricultural land on the property is also being allowed to return to rainforest, but it will take a long time.

We saw more of the Golden Carpenter Ants that we had seen at other places, noticeably Santa Rosa.

As I was editing the photos, I noticed something unusual about this ant. Note the area in the circle. I think this was a reproductive ant (a queen) who had just dispersed from her home nest. She has been on a mating flight and found a good potential nest site. She has just chewed off her wings and is getting ready to start laying eggs and found a new colony.

I'm not sure what caterpillar this is (above and left), but it was large and impressive. It might be a sphingid (sphinx) moth caterpillar.

The Cone-headed Katydid, with the prominent spike on its head (below) was easier to identify.

This tree, near the dining hall, was just LOADED with epiphytes. I think there was more biomass of epiphyte than there was of tree. Bromeliads, ferns, orchids, even cacti were all found in this aerial garden. Even if none of these plants were actually taking water or nutrients from the tree, I think this relationship has gone beyond commensalism as the tree is obviously being hurt.

Fungi were common at La Suerte. An essential part of the ecosystem, fungi are among the few organisms that can break down cellulose, thus without them trees and leaves would remain on the ground for long periods of time without decomposing. The fungi return the nutrients to the soil (and carbon dioxide to the sky). In many cases, the presence of fungal hyphae (filaments) in wood actually increases its nutritional value by raising the protein levels and thus making it possible for insects to feed on the decaying wood and accelerate the decomposition process.

A typical trailside view above one of the streams at La Suerte.

Right: Cows graze in some of the remaining pasture at La Suerte. Most of the former agricultural land at the station is being allowed to revert to forest.

Below left: Living fence, made by cutting sections of trees and planting them close together in the ground. Not only do they not rot, but they actually take root and grow, thus allowing the fence to persist in an area where most wood rots quickly. This fence has been fortified by wire, but often the wire is omitted or the trees are spaced much further apart and used to support wires in a more traditional manner. Different species of trees are used in different regions of Costa Rica to form the living fence.

Below right: Tall trees in the primary rainforest at La Suerte.

Above: The best way for many plants to get their leaves up into the sun is to steal support from an existing tree. This vine is growing up towards the sun; its leaves will stay pressed flat to the trunk until it reaches the canopy. There, the leaves will spread out and shade out the leaves of the host tree.

Loading up the bus to leave La Suerte. In 2007, we went from here to Tortuguero by boat.

Return to Main Costa Rica Page