La Selva...Monkeys! and Snakes! and Frogs! Oh My!

The name of this biological field station is literally "the jungle." And this is certainly the most jungle-y place that we have been in Costa Rica. It is a wet lowland forest, so even during the dry season, it rains every week or so. This makes the whole place very green and lush. There are bromeliads decorating all the trees, just like at Las Cruces, and understory palms with enormous leaves bigger than I am. Because of its large size and location, the reserve is home to huge diversity of wild-life. I see more than five bright red poison dart frogs on a casual walk in the woods--and they look exactly like those plastic figurines in museum shops only a little bit smaller. On a night walk, our visiting herpetology professor spotted a golden eyelash viper curled up on a palm frond. Its gets its name from the eyelash-like scales that extend over its eyes. Pretty neat looking. And howler monkeys cross with suspension bridge spanning the Sarapaqui River. So people can stand eye to eye with the monkeys. (Although monkeys become upset and aggressive when looked straight in the eye--so I don't recommend it.) Along with all the wildlife, La Selva offers high-quality facilities for researchers and student groups (like us!), so the place is always full with more than 40 to 60 people at one time. For researchers, that seems like a great balance of wildlife and social life.

Right now, we are in the middle in another independent project. This time around, I am working with Ben and Forest, another OTS student from New College in Florida. We are studying an ecological concept called "density dependent predation." In a nutshell, this means that if you pack more organisms of the same species in one place, a higher proportion of them will die from competition, predation, and disease. For example, it is easy for squirrels to find and eat all the acorns piled at the bottom of the oak tree and much harder for squirrels to find all the scattered acorns far away from the oak tree. In seeds, this effect usually interacts with distance, as seeds are generally more dense closer to the tree and more spread out further from the tree.

Most studies focus on density-dependent mortality overall from all types of predation. We are trying to see how density-dependent mortality varies with predator type. To do this, we are using Dipteryx panamensis, a large tree in the legume family. Its fruits have sweet green flesh on the outside of the hard, woody endocarp that contains the seed. The fruits are usually dispersed by primates and frugivorous bats that eat the green flesh and discard the seed intact away from the tree base. On the ground, a variety of predators, including bruchid beetles, peccaries, and agoutis, eat and destory the seed and each damages the endocarp in a unique way. And the endocarp persists on the forest floor for years after the seed is gone. (But don't worry, we are confining our study to seeds dropped this year/seeds that have retained some of the fuzzy flesh). So this allows us to measure how much each type of predator preys on the Dipteryx seeds at different distances from the tree and at different seed densities.

Today, the three of us went out on a search for trees and successfully found four. Then we set-up 2 meter by 2 meter plots along a transect at different distances from the tree trunk. We counted the number of seeds that succumbed to each type of damage in the plot. In La Selva, messing around in the leaf litter has its extra "perks." When searching for seeds, I almost poked a hognosed viper. Its venom is supposed to be particularly nasty and their colors make them blend into the leaves. But it is a very beautiful animal with black chevron patterns along brown. So we didn't quite finish finding all the seeds in the snake corner. And to be extra-safe, we poke around in the litter with extra special, snake-proof safety sticks. We also found plenty of more benign critters, like an incredibly adorable turtle, green-and-black poison dart frog, and cart-loads of the red frogs. Fieldwork is such a good time to enjoy the outdoors.

Monteverde

Home of a Quaker community transplanted in the 1950s. Home of delicious cheese. And former home of the Golden Toad. Monteverde definitely rates as one of my favorite sites this semester: pleasantly cool mountain air and mossy cloud forests. Monteverde itself can be an ambiguous place since that name is pinned to the region around Santa Elena, the actual town of Monteverde, and the 3 or 4 private reserves along the mountain. The San Gerardo Station where we stayed for the week is inside of the Bosque Eterno de Los Ninos (Children's Eternal Forest) (which, by the way, has a neat story about its establishment). Although we had limited electricity and no internet, we did enjoy the luxuries of hammocks with gorgeous views of Volcano Arenal and empanadas and coffee every afternoon. They take tourists! So check it out if you don't mind hiking in and out an hour.

Mark Wainwright, a herpologist and incredibly talented naturalist, gave a series of lectures about amphibian taxonomy, frog calls, and the amphibian decline in the 1980s. Mark is one of the best teachers that I have ever seen. He's lectures were so engaging and dynamic, he handled all the questions beautiful, he clearly understood and passionately loved the material. So great!

We'll skip over the taxonomy; I'm not crazy about Latin names. Learning about frog calls gave me a new respect for acoustics. Some frog species will call in choruses, with each frog singing in turn according to a hierarchy. So none of the calls overlap! How do they do that? And the tone of the songs will change with temperature and their hearing also changes with temperatures. Females at 25 C, for example, will respond to recordings of male calls made at 25 C. How crazy is that! Female hearing changes with temperature to match the changes in the male frog calls. And, this is almost the best part, Mark spends a lot of his time as a naturalist searching for frogs and recording their calls. Because there are dozens upon dozens of species out there whose calls we don't know. Without that information, we cannot reliably census frog populations, study their mating behavior, or a million other basic things.

Now here is the short version of the Amphibian Decline: In 1986, a researcher counted 1500 Golden Toads on a ridgetop in Monteverde. This critter lives belowground and only emerges once a year to breed during the heaviest rains. After that researcher secured funding and returned the next year, there were only seven toad. Similar versions of this story played out all across North, Central, and South America, mostly in mountainous regions and mostly in species that lay their eggs in the water. Here are the simple explanations that do not quite seem to fit the entire story: increased ultraviolet exposure from the thinning ozone layer, pesticide residues, disease alone, climate change.

After 20 years of research, scientists think that the frogs died from a very aggressive aquatic fungus that infects their skin. Some scientists think that this fungus was introduced from Africa, so it is an invading exotic. Other scientists have found this fungus in ponds and rivers where they find plenty of healthy frogs. So they think that global warming compounded a particularly harsh El Nino year in 1986 and left the populations more vulnerable to a naturally occuring fungus. So no one really knows. We do know that some species disappeared and some populations were decimated. Now, we have also seen many populations gradually increasing. So there is an almost happy ending to the story.

More on Cabo Blanco and La Selva tomorrow!

Spring Break with the Iberle Clan

I just returned to San Jose from a wonderful week of vacation with Ben and his parents. The trip started off with Osa, the southern, Pacific peninsula that is home to Corcovado National Park. We stayed just a few minutes walk from the entrance to the park and spend the first day hiking.



I've always been told that walking into Corcovado means seeing wildlife, but we had such good luck: scarlet macaws close in the canopy, a troupe of coati chicas drinking from a stream less than a meter from the trail, spider monkeys eating bananas, white-faced monkeys running along the branches, and (the crown jewel of the trip) a tapir.



Tapirs deserve a little more explanation. They are the largest mammal native to Latin America and look like a cross between a small hippo and a horse with a long, flexible, almost elephant-like snout. (Yeah, they are kind of awkward.)



And they are fairly rare and also very important to forest structure since they eat and disperse tree seedlings. I hope to see more tapirs and maybe peccaries, a native wild pig, when I am working on the seedling project with Chris Graham with summer.

When we weren't hiking, I lounged in the hammocks and read or threw a frisbee in the surf with Ben. Very relaxing. Ben and I had a chance to talk to the lodge's sustainability coordinator and resident naturalist, Ifigenia, about conservation on the Osa.

To me, she is a great role model because she approaches conservation very positively and holistically. She engages a wide-range of actions as conservation, from toy collections for indigenous children to recycling programs, from collaborating with women in the community to produce chickens to promoting natural literacy in the community. She accounts for social and cultural, not just environmental needs.



Actively involved in her community, she was bothered by the fact that most of the conservation groups that she saw were large and organized by rich North Americans or Europeans. So she founded ASCONA, the Asociación Costariceñse para la Naturaleza, as the first Tico conservation organization on the Peninsula. It's still very small, but they have taken on very useful, concrete projects on Carate, the nearby town. It would be a great organization for Grinnellians to work with over the summer!



After Osa, we drove to Arenal, an active volcano in the mountains north of San Jose. The cool, misty weather was a welcome change from the heat and humidity of the coast. The volcano first erupted in the 1960s, killing 80 people and thousands of cattle. Since then, it has quietened and the town has exploded with eco-tourism this and eco-tourism that.



We choose to visit the National Park, Butterfly Conservatory, Hanging Bridges, and the EcoThermales Hot Spring. All great choices. The views of the volcano from the hiking trails around its base were amazing. Steam billows from the top and the base is littered with huge gray-colored rocks that had formed during the eruption. Volcanoes are quite impressie-looking.

The hike around the two miles of trails at the Hanging Bridge turned out to be some of the best wildlife watching opportunities we had. Here's the list (not including some birds whose names I don't remember.): 1) Green hermit hummingbird that sat still and chirped for almost ten minutes. 2) Juvenile whiptail lizards with bright, electric blue tails, 3) howler monkeys dangling from the branches, 4) bright red and blue poison dart frog--wow!



I never thought that I would see a poison dart frog in the wild!. And, of course, the canopy and neat leaves, flowers, and fruits from above. A great and worthwhile tourist attraction.

Tomorrow I am off to Monteverde & Cabo Blanco for 2 weeks without Internet. Hooray! When I get back, I will add wonderful pictures of all the animals that I saw. Hasta luego!