Why La Fortuna is a Herpetological Hotspot

Tucked into the northern foothills of the Arenal Volcano, La Fortuna de San Carlos sits at the crossroads of three ecosystems: humid Caribbean lowland forest, premontane rainforest, and secondary regrowth carved by decades of agriculture. That mosaic — plus warm nights that rarely drop below 22°C and rainfall that averages over 3,500 mm a year — makes it one of the richest corners of Costa Rica for reptiles.

In a single guided night walk near the base of the volcano, it’s not unusual to record five or six species. Over a full week of dedicated fieldwork, that number climbs into the twenties. Here are the species most worth traveling for — and how to actually find them.

1. Eyelash Pit Viper (Bothriechis schlegelii)

The undisputed icon. A small arboreal pit viper — rarely more than 60 cm — that comes in a full palette of yellows, greens, browns, and even pinkish morphs. Named for the raised scales above each eye that give it a permanent scowl.

Where to look: low-hanging heliconia stems and palm fronds near streams. Almost always at head-height or lower, coiled and still.
Best time: late afternoon and night walks between April and October.
Field note: venomous. Never approach closer than a meter. A good headlamp, patience, and a guide are all you need.

2. Green Basilisk / Jesus Christ Lizard (Basiliscus plumifrons)

The one that runs on water. Males grow up to 90 cm, sporting a triple crest along the back and tail and an emerald color that looks unreal in dappled light. When startled, they sprint across the surface of streams on their hind legs — physics working in their favor for a couple of seconds.

Where to look: riverbanks and low branches overhanging water. The Río Fortuna and Río Arenal both hold populations.
Best time: mid-morning, when they warm up in patches of sun.

3. Fer-de-Lance / Terciopelo (Bothrops asper)

The most medically significant snake in Central America. Heavily built, cryptically patterned, and responsible for the majority of serious snakebite cases in Costa Rica. Adults commonly exceed 1.5 m; occasional individuals cross the 2 m mark.

Where to look: leaf-litter on forest edges, near old plantations, and along disturbed trails. Do not go looking without a guide — this is a species best observed at a respectful distance with a trained eye leading the way.
Best time: nocturnal and crepuscular.

4. Green Iguana (Iguana iguana)

The largest lizard you’ll routinely see. Adult males with breeding orange coloration can reach 1.8 m nose-to-tail. Fully arboreal as adults, they bask in the canopy over rivers and drop into water when disturbed.

Where to look: canopy of trees over any of the region’s rivers, especially in the dry season (December–April) when they nest on sandy banks.

5. Boa Constrictor (Boa imperator)

The region’s largest snake. Non-venomous, semi-arboreal as juveniles, more terrestrial as adults. Individuals over 2.5 m are regular in the area. Prey ranges from bats and birds to small mammals — a keystone predator in secondary forest.

Where to look: tree hollows during the day, forest floor and low branches at night.
Field note: completely harmless if left alone. Never handle without a permit and expertise.

6. Anolis Lizards (multiple species)

La Fortuna hosts at least five anole species, each in its own microhabitat: Anolis limifrons in low vegetation, Anolis biporcatus higher in the canopy, Anolis humilis in leaf litter. Watching males extend their colored dewlaps in territorial displays is one of the small pleasures of a forest walk.

7. Brown Vine Snake (Oxybelis aeneus)

Impossibly slender, up to 1.5 m long and often no thicker than a pencil. When threatened, it opens its mouth wide to reveal a dark blue-black interior — a startling display for a rear-fanged, mildly venomous snake that is functionally harmless to humans.

Where to look: shrubs and low branches at forest edges. Look for the outline that doesn’t match a real vine — that slight taper toward the head.

8. Helmeted Iguana (Corytophanes cristatus)

Small, prehistoric-looking, and cryptic to the point of invisibility. Grows to about 35 cm, spends the day motionless on vertical stems, and lets moss and lichens grow undisturbed on its skin. One of the most sought-after finds for herpers in the region.

How to Herp La Fortuna Responsibly

Three rules keep both you and the ecosystem safe:

• Never handle venomous species. Photograph, observe, move on.
• Go with a licensed local guide. They know the trails, the venom-protocol, and where the animals actually are.
• Leave no trace. Return rocks and logs to their exact position — many of these animals depend on specific microhabitats.

Best Season for Reptile Watching

The green season (May–November) is peak activity: high humidity, warm nights, active snakes. The dry season is easier for spotting basking lizards but slower for snakes. Nocturnal walks are essential — most species are active after dark.

Ready to See Them Yourself?

Our small-group expeditions in the Arenal region are designed for people serious about reptiles, amphibians, and wildlife photography. Limited spots each season. See upcoming Costa Rica tours →