Everyone Gets Defensive Sometimes

Animals displaying bright coloration and patterning to warn away predators are known as “aposematic,” and include things like coral snakes, skunks, and poison dart frogs (Dendrobatidae). This “blue jeans frog” is bright red and blue as a warning to potential predators that it is very nasty-tasting and/or dangerous to their health… but doesn’t lend them any stealth abilities for avoiding curious and camera-laden humans.

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Other fun facts about these frogs: they lay eggs in the leaf litter, fertilize them, allow them to hatch, and then carry the tadpoles on their backs high into the canopy, to deposit them in tiny pools of water caught in bromeliads. The mother will return to feed them every day until they are big enough to grow legs and leave the pools, somehow remembering each tadpole’s location, and providing them with the chemicals in their foods that they will need to retain their parents’ defensive poison.

Another type of animal defense involves not advertisement of unpalatability but simple hiding-in-plain-sight. Tent-making bats like the two species below chew along the midribs of big leaves, collapsing them down into little shelters. They hold on to the midribs with their tiny little feets, and nap through the day bathed in the green light coming through their tent walls. They also build decoy tents, with no bats inside, possibly to foil squirrel monkeys and other bat predators’ efforts to find their real hiding places.

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These ones look like cotton balls. Way too cute.

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Other interesting defense mechanisms we’ve seen in La Selva include: the armadillos, hard to photograph because they like to crawl around in the underbrush in the dark; fer de lance snakes with a very nasty bite to impart on anything foolish enough to tangle with them; and bullet ants, inch-long little boogers that are named for their ability to make you feel, for 24 full hours, as if you have been shot.

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Then there are things like this tamandua (ant-eater) that see potential predators like us, squeak, and waddle over to a too-small tree in order to climb it slowly and cast timid and unhappy looks down at the scientists below. Not maybe as impressive a defense strategy… but still pretty adorable.

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The Big Hike In

From the ranger’s station at the edge of Corcovado National Park to the Sirena Station, it’s about a 15 minute flight. Or, if you’re Dartmouth Bio FSP, it’s about a 23 km hike along a jungle trail.

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23 km is a long way, especially if you’re carrying three liters of water, binoculars, camera, safety supplies, and doing all of this in 90-degree weather. But the scenery was fascinating and the company was fun. Corcovado is located on the Osa Peninsula, one of the largest stretches of primary-growth lowland rainforest in Central America, untouched by man besides the rough trail and the research/tourist stations farther in, and known to National Geographic as “the most biologically intense place on earth.” The biodiversity is huge and the plants and animals strange and colorful, with giant waxy leaves and bright feathers in the most unexpected places, vines draped across trees like arms around shoulders, and fungi peeking out from the moist clay and crumbling logs.

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The three big nutrient cyclers of the forest are actually quite commonly seen… but easily overlooked. Termites, army ants, and leaf-cutter ants abound and make up a large part of the animal biomass of the forest, astounding for their size. These leaf-cutters were the first we saw this trip, but they soon became ubiquitous along the trail. 

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Among the other exotic creatures was a simultaneously cryptic and vivid poison dart frog- I’m used to seeing these in pictures and behind glass, but to see one in real life was almost unbelievable. It looked like a little plastic toy in the leaves… until it hopped into the jungle.

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The walk took us about seven hours, down red-clay trails and over tree roots, across streams and under the ever-present drone of the cicadas. 

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But we all made it in good health and good spirits to Sirena Station, the intersection between river, beach, and jungle at the edge of the wildest jungle we’ve visited and the biggest ocean on the planet. We could feel the adventure waiting in the air around us… but it could wait until after dinner.

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