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.