The Eyelash Viper

Meet the Eyelash Viper: Costa Rica's Colorful Ambush Hunter

The Eyelash Viper (Bothriechis schlegelii) is one of the most striking and iconic venomous snakes in Costa Rica. It's a small, arboreal pit viper that's easily identified by the modified scales above its eyes that look exactly like eyelashes. It's famous for its incredible polychromatism, meaning it comes in a wide variety of colors, including bright yellow, green, red, and even brown or grey. This variety allows different individuals to blend into specific niches, from bright tropical flowers to lichen-covered branches. It's a master of the ambush, spending days or even weeks coiled in the exact same spot, waiting for a hummingbird or a small frog to wander within striking distance. It's a relatively small snake, rarely exceeding 30 inches, but it's a formidable predator that commands respect.

Top Locations & Tour Suggestions for Eyelash Viper Spotting in Costa Rica

Eyelash Vipers are found in humid lowland and cloud forests throughout the Caribbean and Pacific slopes. To see them, you could join a specialized wildlife expedition in one of these prime habitats:

• Cahuita National Park: The coastal forest trails here are famous for yellow eyelash viper sightings, often resting in the leaves just inches from the path. To see them, you could join our Cahuita National Park Guided Hike, where our local experts will help you spot these snakes tucked into the low-level vegetation near the shoreline.

  
  

• Tortuguero National Park: The low-hanging branches along the Caribbean canals are a favorite spot for these vipers to hunt for frogs. To see them, you could join a Tortuguero Canoe Wildlife Tour, where expert guides can spot them perfectly camouflaged among the water-side foliage.

  
  

• Arenal and La Fortuna: The secondary forests and dedicated frog gardens around the volcano provide excellent habitat. To see them, you could join an Arenal Night Walk, which is the best way to see them active after dark.

Frequently Asked Questions about Water Opossum in Costa Rica

Why do they have eyelashes?

Scientists believe these scales, called supraciliary scales, help break up the outline of the snake's eye. This makes it harder for prey and predators to recognize the snake's head while it's hiding among leaves and flowers. It may also help protect the eyes as the snake moves through thick, thorny vegetation in the canopy.

Are they deadly to humans?

While they're highly venomous, they're rarely fatal to healthy adults if medical treatment's sought quickly. Their venom is hemotoxic, meaning it breaks down tissue and affects blood clotting. Because they're small, they don't produce as much venom as a larger snake like a Fer-de-Lance, but a bite is a serious medical emergency that requires antivenom.

How do they stay on a branch without falling?

They have a fully prehensile tail that acts like a fifth limb. They wrap the end of their tail tightly around a branch or vine, which allows them to stretch their entire body out into the air to strike at a bird or lizard without losing their grip. It's a vital tool for a life spent entirely off the ground.

Can they change their color like a chameleon?

No, they can't change their color. The color they're born with is the color they'll have for their entire life. However, a single litter of babies can contain multiple colors, such as one yellow, one green, and one brown sibling. This is a genetic strategy to ensure that at least some of the offspring will be well-camouflaged in whatever environment they end up in.

What do they do if you get too close to them?

They're generally very calm and will rely on their camouflage to stay hidden. They don't want to waste their venom on something they can't eat. If you get too close, they'll usually stay perfectly still, but if they feel threatened, they'll coil into an S-shape and strike with incredible speed. It's always important to look before you grab a branch in the rainforest.

Social Status: The Solitary Ambush Specialist

The social life of an Eyelash Viper is strictly solitary. They don't live in groups, and they don't even like to share the same hunting branch with another adult. Each snake chooses a specific hunting site based on the presence of prey, such as a flowering plant that attracts hummingbirds. They're very patient and will stay in the exact same position for days at a time. They don't defend a specific territory in the way a mammal does, but they'll move if another predator or a larger snake enters their immediate space. Outside of mating, they avoid all interaction with their own kind to focus entirely on their own survival.

Finding a Mate: The Dance of the Vipers

When a male is looking for a mate, he'll follow the scent trails left by a female on the branches. When two males meet near a female, they engage in a ritual called the dance of the adders. They'll raise the front half of their bodies and try to push each other down. It's a test of strength, but they don't bite each other. The winner gets the chance to mate with the female. Once the mating's finished, the pair separates, and they go back to their solitary lives in the canopy.

Birth: A Live-Bearing Strategy:

Unlike many other reptiles that lay eggs, the Eyelash Viper is ovoviviparous. This means the mother carries the eggs inside her body until they're ready to hatch. When the time comes, she gives birth to live, fully formed young. A typical litter can have between 6 and 20 babies. Giving birth to live young is a huge advantage in the rainforest because it protects the developing offspring from egg-eating predators like monkeys and birds. The babies are born with a full supply of venom and they're ready to hunt immediately.

Parenting: Independence from Birth

There's absolutely no parenting in the world of the Eyelash Viper. Once the babies are born, the mother's job's completely finished. She doesn't protect them or feed them. The young snakes have all the instincts they need to survive. They'll immediately crawl away to find their own hidden spots in the low vegetation. They often use their brightly colored tails as a lure, wiggling them to attract small frogs or insects. This is called caudal luring, and it's a vital skill that helps them survive their first few months of life.

Habitat: The Vertical World of the Rainforest

Eyelash Vipers are strictly arboreal, meaning they're almost never found on the ground. They prefer humid lowland forests, premontane forests, and cloud forests. They're most common in areas with thick foliage, vines, and epiphytes like bromeliads. They're often found in heliconia plants and palm trees, where the large leaves provide excellent cover. In Costa Rica, they're found on both the Caribbean and Pacific slopes, though they're absent from the very dry forests of the northern Pacific coast. They require high humidity to maintain their health and to keep their skin from drying out.

Daily Life: The Long Wait for a Meal

A day in the life of an Eyelash Viper is a masterclass in patience. They don't actively hunt for food by moving around. Instead, they choose a spot where they know prey will pass by. They'll coil their body into a tight ball and rest their head on the top, staying perfectly still. They have heat-sensing pits located between their eyes and nostrils that allow them to see the heat signatures of warm-blooded animals like birds and mice. This allows them to strike accurately even in total darkness. They spend most of their lives waiting, only moving when they need to find a new hunting spot or a mate.

Behavior: The Precision Strike

Their most famous behavior is their lightning-fast strike. When a bird or frog gets close enough, the viper will launch the front half of its body forward. Because their tail is anchored to a branch, they can strike out into the air and pull themselves back in once they've grabbed their prey. They have long, hollow fangs that fold back against the roof of their mouth when not in use. When they strike, the fangs swing forward and inject a potent dose of venom. They usually hold onto their prey until the venom takes effect, then they swallow it whole, starting with the head.

Ecological Role: The Canopy’s Pest Control

Eyelash Vipers play an important role in the rainforest ecosystem as mid-level predators. By hunting small mammals, birds, and frogs, they help keep those populations in balance. This prevents any one species from becoming too dominant and damaging the forest's vegetation. They're also an important food source for larger predators. Birds of prey like the Laughing Falcon are specialized in hunting snakes, and they'll often pluck Eyelash Vipers right off their branches. They're a vital link in the complex food web of the tropical canopy.

Predators: Danger from Above

Despite being venomous, Eyelash Vipers have many enemies. Their biggest threats are large birds of prey and other snakes. The Laughing Falcon and the Great Black Hawk are both experts at spotting camouflaged vipers. Some larger snakes, like the Mussurana, are immune to their venom and will actively hunt and eat them. Mammals like coatis and monkeys will also kill them if they feel threatened or if they're looking for an easy meal. Their primary defense is their camouflage; if they can stay hidden, they stay safe.

Interesting Facts about the Eyelash Viper

• The yellow version of the Eyelash Viper is often called the oropel and it's one of the most photographed snakes in the world.

• They can survive for several months without eating a single meal because they have a very slow metabolism.

• They're the only species in their genus that shows such a wide range of different colors.

• Their eyelashes are actually just modified scales and are not made of hair like a mammal's eyelashes.

• They're often found in the same hunting spot for weeks at a time and researchers have even named individual snakes based on their favorite branches.

Culture and History: The Beautiful Danger

Historically, the Eyelash Viper has been a figure of both fear and fascination in Costa Rica. In many local stories, they're seen as the guardians of the forest because they're so well-hidden and are often found at eye level. While they aren't as feared as the larger Fer-de-Lance, they're respected for their ability to strike without warning. In the past, they were often killed on sight near plantations, but today they're a major draw for eco-tourism. They've become a symbol of the beauty and hidden danger of the tropical rainforest, and seeing one is a highlight for any wildlife photographer.

The Science of the Heat-Sensing Pits

The Eyelash Viper is a part of the pit viper family, which means it has a specialized organ called a loreal pit. This pit is a heat-sensing organ that's located on each side of the face between the eye and the nostril. It contains thousands of sensitive nerve endings that can detect even the smallest changes in temperature. This allows the snake to create a thermal image of its surroundings. It's so sensitive that the snake can detect a warm-blooded animal from several feet away, even if it can't see it with its eyes. This is a massive advantage for hunting at night or in the dark, shaded areas of the canopy.

Communication: Scent and Vibrations

While snakes don't have ears or vocal cords, they're not completely isolated. They communicate primarily through chemical signals and vibrations. They have a specialized organ called the Jacobson's organ in the roof of their mouth. When they flick their tongue, they're collecting chemical molecules from the air and the branches. This allows them to smell the presence of prey, predators, or potential mates. They're also very sensitive to vibrations in the branches, which tells them if a large animal or a bird is approaching long before they can see it.

Conservation: Protecting the Vertical Forest

In Costa Rica, the Eyelash Viper is currently not considered endangered, but they're very sensitive to habitat loss. Because they live in the canopy, they need large, connected areas of healthy forest to thrive. If the forest is cleared for agriculture or development, the snakes lose their hunting grounds and their protection from predators. Conservation groups are working to protect the large tracts of primary forest that these vipers (and many other creatures) call home. Supporting sustainable tourism and avoiding the use of pesticides helps ensure that the insect and frog populations they depend on stay healthy.

Tips for Travelers and Photographers

• Look in the Heliconias: They love to hide in the colorful bracts of heliconia flowers, especially the yellow ones.

• Don't Touch the Branches: Always look where you're putting your hands. They're masters of camouflage and will often be at eye level.

• Use a Macro Lens: To capture the detail of the eyelashes and the scales, a macro lens is essential. You can get incredible shots from a safe distance of three or four feet.

• Go with a Guide: Professional guides in Costa Rica have a trained eye and can spot vipers that you'd walk right past.

• Watch the Strike Zone: If you find one, stay at least five feet away. They can strike up to half their body length, so it's always better to be safe than sorry.