Inside the Tropical Wet Forest

La Selva Biological Station is the epitome of a tropical rainforest (although by Holdridge life zone classification it is actually a tropical wet forest, experiencing a wet and a wetter season as opposed to a full year of downpours) and is OTS’s most popular field station for researchers.  Located at the junction of two rivers in the province of Herendia, La Selva (literally “The Jungle”) is home to the widest diversity of wildlife we’ve experienced in all of our time in Costa Rica.  Walking down any of the various trails that surround the station, crossing the famous hanging bridge, or even just sitting on a bench in one of the open areas on campus, you’re bound to see some amazing creatures.

la selva bridge

DSCN6453 Hanging bridge (above) and, on the other side, Sendero Tres Rios (Three Rivers Trail; below) at La Selva Biological Station.


Our first class at La Selva consisted of no textbooks or powerpoint presentations, but simply a nature tour through the trails in order to begin to learn the landscape.  Peccaries were the first to greet us at the trail’s entrance.  While strange and exciting at first, these “pets” of the station would come to elicit no more than a sideways glance within just a few days.

peccaries 1

peccaries 2 Collared peccaries, eating and lounging around campus

Less than three steps onto the trail we spot one of the iconic creatures of the tropical rain forest habitat: the strawberry poison dart frog.  About the size of a thumbprint, these aposematically colored frogs advertise their toxicity to predators, making them easy to spot amid the collage of greens and brown that composes the forest floor.

strawberry too

Strawberry poison dart frog (also called the blue-jean frog–can you see why?)

During our hike, we encountered some old favorites from our days at Las Cruces, including the crested guan, chestnut-mandibled toucan, and Cherri’s tanager.  New to the list was the collared aracari, considerably smaller than the other toucans we’ve seen and sporting rich flame-colored feathers and bill.  These guys have become a fairly regular sighting in the open areas on campus or in trees towering over the hanging bridge, but every time they’re as surprisingly stunning as the first.

collared aracari

Collared aracari

Rounding out our tour was one of La Selva’s notably precious rarities—the eyelash pit viper.  This venomous snake that could fit in the palm of your hand when neatly coiled gets its name from the two small scales that protrude vertically above each eye.

eyelash pit viper - rachel moon

Eyelash pit viper (Photo credit: Rachel Moon)

The structure of the station is expertly done, creating spaces that are conducive to seeing animals up close without being in their way.  Sitting at breakfast in the open-air dining room, you can watch as kiskadee parents gather dragonflies, berries, and whatever else they can find to feed their chicks in the nest tucked against the side of the building.  Both parents make trips to the nest, never letting more than five minutes or so pass without providing another snack for their offspring.  The constant peeping from the little ones reminds the parents that no matter how much they get fed, they still have room for more.

kiskidee with dragonfly

Great kisdadee with a dragonfly meal

kiskidee nest

Great kiskadee chicks begging for food in the nest

kiskidee feeding time

Parent returns to nest to feed chicks

While crossing the hanging bridge to get to class, this rufous-tailed jacamar zipped just over our heads and landed on the top of a tree, which is nearly at eye-level when standing on the bridge.  After a moment’s rest it flew up again so quickly that it nearly vanished from sight, and in one swift movement returned with a butterfly flattened within its beak.  We watched as it literally tore the insect to shreds through a combination of thrashing its head and making quick snapping motions with its beak.

jacamar feed

A hungry jacamar

On an early-morning hike to beat the heat, we crossed paths with another poison-dart frog, this one of the green and black variety.  As it hops about in and under the leaf litter, I’m reminded of its plastic toy replica I played with as a kid.  A bit further along, this glasswing butterfly flutters out of the forest edge, disappearing and reappearing before our eyes.  When it finally lands on a leaf, we see that its wings are completely transparent.  It seems like tropical creatures have much more creative ways of evading predation than prey in the temperate zone, whether they are flaunting their unpalatability or making their predators dizzy with confusion.


Black and green frog


Glasswing butterfly


Crossing the bridge once more in the late afternoon to get home to our comfy cabins, I see something large and hairy crawling along the bridge cable.  A sloth?  But wait, it’s moving, and not in slow-motion.  Getting closer, its form becomes clear: a howler monkey!  And she’s with her baby, too.  The pair sits less than five feet above my head, tails wrapped around the cable for support and relaxed gestalt suggesting that they barely notice me at all.

howlers bridge

Howler monkeys on the bridge


Walking around La Selva, ecological questions come naturally.  Why do leaf-cutter ants travel so far from their nests and to the top of the canopy to gather leaves?  What drives variation in the amount of blue and red coloration in strawberry poison dart frogs?  What do all of the different oropendola calls mean to the other birds?  How did so many types of drip-tips on plant leaves evolve?  And why is it that the tropics have so much biodiversity?

Regrettably, intriguing questions such as these are difficult to tackle in four days, which is the allotted time we have to conduct an independent research project here at La Selva.  Building on experience from our jacana study back in Palo Verde, I’ve discovered that the key to a successful project is to choose a study organism that is 1) interesting, 2) abundant, and 3) at least somewhat cooperative.  For me, it was a no-brainer: the strawberry poison dart frog.  Since the males of this species spend all day calling, usually from a conspicuous perch, there were plenty of interesting directions from which to examine their acoustic behavior.  The question, how we did it, and what we found coming soon!

2 comments to Inside the Tropical Wet Forest

  1. Judy says:

    Wow, this sounds like quite a place. At every turn, another wonderful, diverse sight of nature! Those action shots are great.

  2. Cary Stuebing says:

    Beautiful photography!
    Love those howler monkeys!

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