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Notes from the Rio Cuyabeno

Updated: Dec 4, 2023


Today we left for the Cuyabeno Wildlife Reserve, Ecuador's second largest protected area after Yasuni National Park just to the south. We are now in Lago Agrio, a pioneer oil town that is responsible for the production of over 21 billion barrels of oil and the devastation of large tracts of Amazon rainforest. Surprisingly, Lago Agrio is a much nicer looking town than I had imagined it to be, complete with a well-lit main street and outdoor dining. Our hotel was complete with cable, air conditioning, hot water and a pool and we were able to use free internet for some time last night.

Cuyabeno Wildlife Reserve is located in the Amazon of northeastern Ecuador in the province of Sucumbíos. It is the second largest protected area in the country after Yasuní National Park, just to the south (Image from

Leaving Lago Agrio, we passed by giant tanks with the letters PETROECUADOR printed across them. This Nationally-owned company was formed several years ago, taking over Chevron-owned Texaco, the US-based company responsible for contaminating the lakes and rivers that hundreds of indigenous communities depend on. Prosecutors claim that Chevron intentionally dumped 18 billion gallons of toxic oil wastewater into the rivers which has coincided with elevated rates of cancer, pre-aborted babies, and birth defects among local inhabitants. The people of Ecuador sued Chevron for 1 billion dollars, resulting in the largest international environmental lawsuit ever.

It turns out, the case now has no credibility because of a corrupt Ecuadorian judge who accepted a three- million dollar bribe to rule against Chevron appeals. After the case was brought to Lago Agrio in 2007, it seems the politicians and their cronies couldn’t keep their messy hands out of the trial.

Setting out on the trail from Lago Agrio, it seemed as if we were headed into the middle of nowhere. The oil pipelines lined the mostly paved road and the horizon became lined with flat, dense vegetation. We passed a small creek with a dugout canoe, above which welders stood on a bridge soldering steel that read Made in Ukraine. A solitary white-eared jacamar (Galbalcyrhynchus leucotis) sat perched on a snag and further down the road, an armed guard stood watch in a tower above some filthy fortress. The soils were stained a blood red from iron-oxides formed by constant weathering and the road into the jungle was cut back from sprouting weeds. The trees loomed large over our heads and the darkness and humidity of the rainforest engulfed us.

In the heart of Cuyabeno with Peace Corps buddies Mike and Jacob

In a dugout canoe, we wound our way up a sinuous river surrounded by dense vegetation. A loud buzz of cicadas harassed our ears and erratic, magnetically blue Morpho butterflies fluttered past us one by one. We stopped and craned our necks to observe a Linnaeus's two-toed sloth (Choloepus didactylus), frozen in time on a leafless branch. Rounding a bend in the river, the snake-like neck of an anhinga (Anhinga anhinga) caught our attention as it swayed back and forth as the bird eyed a fish in the murky water. Minutes later, the branches above our head shook with force as several Monk saki monkeys (Pithecia monacus) traversed the canopy. I wondered how they could survive the tropical heat with their thick bushy tails and shaggy manes. In a few short hours, the river began to open up and we had reached the Igapó: a seasonally flooded forest. The water beneath us had been transformed from a thick coffee-brown to a seemingly impenetrable black.

A Linnaeus's two-toed sloth (Choloepus didactylus) hangs motionless above us. Two-toed sloths are nocturnal and come down from the canopy only to change trees and poop

The anhinga (Anhinga anhinga) sometimes resembles a snake as it swims with its neck and head above the water. Its feathers are not waterproof, which allows the body to sink beneath the surface so that it can stalk fish

This photograph of a Monk saki (Pithecia monacus) leaves much to be desired, but I felt fortunate to actually capture an image. Saki monkeys are incredibly shy and wary and stay high in the treetops where they often cannot be seen

Entering the labyrinthine Igapó, a seasonally inundated forest dominated by Macrolobium trees

As we rowed into the middle of the laguna grande away from the river, we noticed a considerable difference in our surroundings. It almost felt as if we had entered a coastal mangrove ecosystem. In fact, one of the more common trees resembles the coastal species so much that it has been given the Spanish name manglar falso. It is actually a tree in the Fig family Ficus.

The entry sign at the Cuyabeno Lodge with russet-backed oropendola (Psarocolius angustifrons) nests hanging from the branches of a Mahogany (Swietenia macrophylla) tree

We were looking at the emergent canopy of an inundated forest. Between the months of October and March, rainfall decreases and the water levels substantially fall. So much water retreats back into the Cuyabeno River that is is actually impossible to reach the Cuyabeno Lodge by boat, which is now an island surrounded by water. In the dry season, the bird watching and wildlife viewing is spectacular due to the numbers of small fish stranded in the shallows and mud flats. Indigenous people like the Siona, Secoya, and Cofan come to the dried lagoon to fish along with migratory birds and hungry mammals.

What’s most amazing to me is that the biggest trees in the lake, the Macrolobium, have adapted to spending nine months of each year completely inundated and three months out on the dry mudflats. These trees are great places to look for Anaconda (Eunectes murinus), for they use the draping branches for resting perches after a big meal. Another tree that was pointed out was Guito (Genipa americana), the fruit of which is used by many Indians to paint their bodies black. Previously, I had only seen this tree on tierra firma - dry land - on farms in western Ecuador, but here it was standing in two to three meters of water!


It’s impossible to sleep past 6:30 am here. The belligerent calls of several troops of yellow-handed titi monkeys (Callicebus torquatus) and the bizarre gurgling song of russet-backed oropendolas (Psarocolius angustifrons) can wake even the deepest sleeper. The fact that the beds here are far from comfortable doesn’t help either.

After enjoying a breakfast of fresh papaya, eggs and fried plantains, Mike, Chauncey, Jacob, and I took a stroll around the island. A troupe of black-mantled tamarins (Saguinus nigricollis) peered out from behind the vines and one came out into the clearing, as if it were searching for handouts. As we walked along the trail, we stirred up dozens of colorful butterflies that were warming their wings up in the morning sun.

A black-mantled tamarin (Saguinus nigricollis) approaches us near the lodge

A Jemadia hewitsonii butterfly warms its wings in the Amazonian sunshine. These butterflies lap up mineralized moisture from the ground beneath them

Today we had an action-packed day with early morning birding and a sweaty two-hour hike into tierra firma forest where we learned about rainforest ecology. On our way to the canoe, we were graced by the presence of a green vine snake (Oxybelis fulgidus) climbing higher into the trees. The pointed snout and vibrant yellow-green belly popped as the snake slithered its way up into the trees.

The green vine snake (Oxybelis fulgidus), hunts from the top down. It identifies its prey, usually a small rodent or lizard on the forest floor, and strikes downward from atop a perch. The vine snake has two larger teeth at the back of its mouth, which it uses to inject toxic saliva into its prey. This venom is fast-acting on small animals but is harmless to humans

The dugout canoe awaits us on the laguna grande

We paddled out across laguna grande listening to the cheerful songs of red-capped cardinals (Paroaria gularis) and watching them fly in and out of the copious Macrolobium trees. One red-capped cardinal nest was found built in the roots of a Macrolobium sitting in standing water. I thought about how many species of birds could be living in the forests around me; some say as many as 580!

Later in the afternoon, we stopped near a bank lined with moriche palms (Mauritia flexuosa) palms. Here, we cast lines to fish for red piranha (Pygocentrus nattereri), which we successfully caught with chicken bait. Before sunset, we traveled to the middle of laguna grande where we could swim without risk of being swarmed by schools of hungry piranha. Apparently they prefer the shallows near banks.

The moriche palm (Mauritia flexuosa) was a tree that fascinated the naturalist Alexander von Humboldt when he first recorded it in 1800 while he traveled through the Venezuelan llanos. He "observed with astonishment how many things are connected with the existence of a single plant," essentially describing it as a keystone species. However, the term would not be explicitly defined until 1969 by Robert T. Paine

The red piranha (Pygocentrus nattereri) were quite easy to catch. We caught six in a half hour of fishing

Who wouldn't want to swim with anacondas, candirus, and black caimans?

We returned to the lodge for dinner to work up the energy for a night hike. After a heavy downpour, we set out to the other side of the lagoon in the canoes. The boat ride was magical. The reflections of the inundated Macrolobium trees were so vivid I didn’t know whether I was looking at the surface of the water or the tree trunks extending down into the water. Like an optical illusion, it appeared as if one could see clearly through the water to the submerged trunks. This really wasn’t the case, but it nonetheless gave us the feeling of hovering above some crystal realm in the canopy of the tallest of forests.

A spectacled caiman (Caiman crocodilus) remains motionless, doing its best to avoid detection. We regularly noticed spectacled caiman throughout the lagoon. However, the much larger black caiman (Melanosuchus niger) eluded us.

Arriving at the far bank, we dismounted from the canoes and quietly hiked into the dense tropical rain forest. Headlamps ablaze, we watched for movement in the canopy, while keeping close tabs on the forest floor. The panoply of life that presented itself was mind boggling. Here are a few photos from the hike:

The Brazilian wandering spider (Phoneutria fera) is also known colloquially as the "banana spider," for its habit of hiding in banana leaves. Spiders in this genus are one of the few species of spiders that present a threat to humans. Its bite is toxic and can cause respiratory failure. Females tend to be more toxic than males.

I have no idea what made this. It looks like a cocoon of some kind

A banded tree anole (Anolis transversalis) pretends to be a part of the tree, unsuccessfully.

This Manaus Spiny-backed frog (Osteocephalus taurinus) was hanging out on the showerhead in the bathroom after we got back from our hike


Even during the day, the reflections on the water’s surface are remarkably vivid. This is due to the high concentration of tannins in the water from dissolved organic material – the water is so black that light appears to be refracted in all directions. Although this site would be incredibly poor for scuba diving or snorkeling on account of the low visibility, it makes for a surprisingly pleasant eco-tourism destination. This is because these very same tannins acidify the waters to such a degree that they prevent mosquitos from breeding here. I can’t believe how few bugs there have been here and I’m not complaining. It is very relaxing!

A Macrolobium tree and its reflection in the ink-black water of the laguna grande

Jacob and Mike search the vegetation for wildlife along the banks of the Cuyabeno River

Our guide Sulema, is a petite, long-haired indigenous woman with a red scar on her right cheek. She is engaging and charming although shy and somewhat withdrawn. She has taught us a number of interesting facts about the jungle, including showing us a palm in the family Astryocaryum that is known as the Walking Palm or Grater Palm. In response to gaps in the canopy, the trunk sends out new roots which are propped above the ground where there is adequate sunlight and shed its roots that are bathed in shade. Thus, over time, the palm actually walks across the forest floor! It is also known as the Grater Palm because the roots are loaded with sharp spines used as a defense to ward off invading insects or hungry mammals and the Indians use them as combs or grates.

Other highlights on the walk included a bizarre, multi-dimensional cocoon, a giant tree in the Malvaceae family with hollow buttress roots that can be whacked with a stick to generate a resonating thump that can be heard for miles. Useful to someone who may be lost in the rainforest. And many insects, from ants and termites to butterflies and beetles.

My favorite feature thus far has been the abundance of an odd bird known as the Hoatzin, or stinky Turkey to the local Indian tribes. This turkey-sized bird belongs to its own family and resembles no other living creature. It is uncannily prehistoric looking, with bright blue markings on the cheeks, red-orange eyes, and tall yellow crest on the head. These birds are perhaps our closest extant relatives to the dinosaurs – a living archaeopteryx. Recently-hatched chicks have claws resembling that of a dinosaur which help them climb back up to the nest from lower branches. They are unique in their diet as well, eating only leaf material from the palustrine trees they inhabit. Consequently, their stomachs are well-equipped with an abundance of microbs that help them digest cellulose-rich substances. These very same microbes give the hoatzin a very disagreeable odor and taste, which can explain why they are so abundant here. They are thus given the name “Stinky Turkey” and are not hunted.


I’ve read about how difficult it is to spot wildlife in the rainforest and today we verified that statement. A full day of birdwatching yielded only 5 new species, but we did have success with other animals. This morning we exchanged our canoes for paddleboats that eased through narrow passageways. We even had to lay down on our backs to limbo under overhanging branches and dodge spiny bushes. It was eerily quiet for most of the morning, with a brief visit from a collared Trogon. Later in the afternoon, we were graced by the presence of 4 pink river dolphins, each one playing gleefully in the glistening waters. This sighting was substantially better than the first, for the cetaceans jumped and lifted their beaked heads friskily, giving us ample viewing opportunities.

The clouds billowed heavily in the open skies around us and we tried to hurry back to beat the rains. Our excursion was delayed by several misguided attempts to head in the right direction. Our lead at the time, Mike Wilcox, was so bad at paddling I gave him the name “Sureshot” Wilcox. In one of his sub-par navigation manoevers, he even managed to snag his baseball cap on a nearby branch and it fell into the river. In an attempt to rescue the hat, Chauncey and I were attacked by biting ants and we were forced to abort the mission, retiring the hat to the bowels of the black lagoon.

Bird List

1. Roadside Hawk

2. Russet-backed Oropendola

3. Anhinga

4. Cocoi Heron

5. Rufescent Tiger Heron

6. Ringed Kingfisher

7. Amazon Kingfisher

8. Greater Ani

9. Red-capped Cardinal

10. Purple-throated Fruitcrow

11. Cattle Egret

12. Hoatzin

13. Maroon-tailed Parakeet

14. Yellow-rumped Cacique

15. Blue-gray Tanager

16. Neotropical Cormorant

17. Orange-winged Parrot

18. Plumbeous Pigeon

19. Lesser Kiskadee

20. Lineated Woodpecker

21. Black Vulture

22. Tropical Kingbird

23. Dusky-billed Flycatcher

24. Large-billed Tern

25. Neotropical Palm Swift

26. Gray-breasted Martin

27. Masked Tityra

28. White-throated Toucan

29. Pale-vented Pigeon

30. Amazon White-tailed Trogon

31. Orange-backed Troupier

32. White-collared Swallow

33. Black-fronted Nunbird

34. White-eared Jacamar

35. Violaceous Jay

36. Ivoy-billed Aracari

37. Palm Tanager

38. Gilded Barbet

39. Striated Heron

40. Collared Trogon

41. Green Kingfisher

42. Squirrel Cuckoo

43. Groove-billed Ani

44. Crimson-crested Woodpecker

Mammal List

1. Black-mantled Tamarin

2. Monk's Saki

3. Squirrel Monkey

4. Yellow-handed Titi Monkey

5. Capuchin Monkey

6. Howler Monkey

7. 2-toed Sloth

8. Pink River Dolphin

9. Long-nosed Bat

Reptiles and Amphibians

1. Spectacled Caiman

2. Green Vine Snake

3. Amazonian Tree Boa

4. Osteocephalus taurinus (frog)

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