Yasuní National Park herping trip report

Articles | Trip reports

By Jasmine Vink. March 2019.

Fringed Leaf-Frog (Cruziohyla craspedopus)

Fringed Leaf-Frog (Cruziohyla craspedopus). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

The Amazon. Two words that instill a sense of yearning and wonder in naturalists the world over. This is a region that appears on the bucket lists of scores of wildlife enthusiasts, myself included. The Ecuadorian Amazon encompasses only a tiny percentage of the 5.5 million km2 considered Amazon rainforest within the basin. Don’t be fooled by its relative small size, the Ecuadorian Amazon, Yasuní specifically, is considered to be the most biodiverse region on earth. A plethora of insects, birds, mammals, and plant life call this region home. What my visit focused on, however, was the herpetological diversity. From the heaviest snake on earth to the most delicate translucent glass frog, Yasuní National Park presents a herp lover’s paradise.

Amazonian Poison-Frog (Ranitomeya ventrimaculata)

Amazonian Poison-Frog (Ranitomeya ventrimaculata). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

I spent six nights traversing the rainforests of Yasuní with my partner, Jannico, and an incredible field biologist from Tropical Herping, Jose Vieira. Unfortunately the conditions were drier than usual but even given how ‘quiet’ the rainforest was we were able to find and identify 66 species of reptiles and amphibians. We stayed at a research station and started our nights at dusk, not arriving back until the early hours of the morning feeling a mixture of exhaustion and awe with the species we had managed to uncover.

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Herping in the Amazon is similar to many areas of the tropics, with your neck craned upwards scanning for the iridescent bellies of sleeping snakes. With a head torch the eye shine of frogs can be seen in the canopy and amongst the dense leaf litter on the forest floor. Tiny sleeping salamanders and colourful poison dart frogs can be spotted with a keen eye on low hanging vegetation. While active terrestrial snakes need a quick reaction as they threaten to disappear into the complex subterranean habitats. Herping the Amazon is no walk in the park but you are rewarded with some of the worlds most unique and spectacular species.

Two-lined Forest-Pitviper (Bothriopsis bilineata)

Two-lined Forest-Pitviper (Bothriopsis bilineata). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

Within hours of our first night I managed to eye shine one of our main Amazon targets. Popularly kept in captivity, the Amazon Horned-Frog (Ceratophrys cornuta) is a master of camouflage. Their intricate patterning coupled with textured skin results in them appearing eerily like a dead leaf. They use this remarkable camouflage to ambush their unfortunate prey. They are indiscriminate with their prey choice, launching their disproportionately large mouths on anything smaller than them. This includes small mammals, other frogs (including members of their own species), snakes, insects, and other unlucky species.

Amazon Horned-Frog (Ceratophrys cornuta)

Amazon Horned-Frog (Ceratophrys cornuta). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

Another frog that exhibits superb camouflage and another species we had high on the wish list is the Fringed Leaf-Frog (Cruziohyla craspedopus). This species is rarely seen given their occupation of the high canopy. They generally only descend closer to the ground during breeding season, when males call for a female from 2–10 meters above the ground. Their colouration is a green background with irregular white patches used to blend in with leaves as they sleep during the day. The fringes on their legs and chin further assist with their camouflage as they help to break up the shape of the frogs for potential predators to identify.

Green Anaconda (Eunectes murinus)

Green Anaconda (Eunectes murinus). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

One of our main snake targets was the Green Anaconda (Eunectes murinus), although Jose unfortunately informed us that he had never found an anaconda at this research station. On our second night, while checking the drainage lines behind the accommodation, Jose spotted our dream species, a small anaconda lying coiled under the water. This is the heaviest snake in the world, weighing up to 100 kg and reaching an incredible length of over 5 meters. Our individual was only a small juvenile but beautifully patterned with a curious nature.

Ornate Coralsnake (Micrurus ornatissimus)

Ornate Coralsnake (Micrurus ornatissimus). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

Coming from the land of elapids (Australia) we were particularly excited to tick off some coral snake species. These highly venomous elapids are brightly coloured in an array of reds and oranges with white and black bands. While walking one of the forest tracks, Jannico spotted an Ornate Coralsnake (Micrurus ornatissimus) cruising amongst the leaf litter. This species, as we were informed, is one of the rarest to see in the Amazon. This species, like most coralsnakes, prefers to feed on other snakes.

Bridled Sun-Gecko (Gonatodes concinnatus)

Bridled Sun-Gecko (Gonatodes concinnatus). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

The Bridled Sun-Gecko (Gonatodes concinnatus) is a fantastic example of sexual dimorphism. The female of this species is a drab brown and grey mottled colouration while the male is a spectacular bright orange with blue and yellow spots. These geckos, unlike most other wildlife, are able to take advantage of human impact in the Amazon.

Upper-Amazon Salamander (Bolitoglossa altamazonica)

Upper-Amazon Salamander (Bolitoglossa altamazonica). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

Other Amazonian species are not so easy to spot, living deeper in the rainforest far from human infrastructure. The Upper-Amazon Salamander (Bolitoglossa altamazonica) is a tiny species of salamander reaching just under 5 cm in snout-to-vent length. These salamanders are highly territorial with males watching over the females in their domain. We witnessed a territorial dispute between males on low hanging vegetation. A standoff ended with the smaller male dramatically leaping off the leaf and onto the ground.

Helmeted Brooding-Frog

Helmeted Brooding-Frog (Hemiphractus scutatus). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

Even given the spectacularly colourful species we were able to see on our trip, my standout favourite was the somewhat bland Helmeted Brooding-Frog (Hemiphractus scutatus). We found a few small individuals of this elusive species before finding a large female with eggs. This species is unusual, only sharing similar reproduction with few species the world over. Unlike most frogs their eggs don’t hatch into tadpoles that develop in water, instead the fertilized eggs are carried on the back of the female for up to eight weeks. These eggs directly develop into perfectly formed tiny froglets on the mother’s back. This behavior is something that is rarely seen and something we all found incredibly interesting to witness. The egg casings are clear giving you an unobstructed window into the developing froglets.

Crowned Dwarf-Caiman (Paleosuchus trigonatus)

Crowned Dwarf-Caiman (Paleosuchus trigonatus). Yasuní National Park, Ecuador. Photo by Jasmine Vink.

After a couple of unsuccessful attempts to access the lagoon due to flooding we accepted that we would not have the opportunity to see a caiman this trip. At 3:00 am, as we were quickly walking back to the research station on our last night, Jannico and myself spotted a large eye shine ahead. It was a Crowned Dwarf-Caiman (Paleosuchus trigonatus), unusually occupying one of the small and shallow streams that run through the hiking trails. Dwarf caimans are an extremely well armored crocodilian. They have bony scutes lining their neck and back, giving them their common name of ‘crowned’. These scutes protect them from predators, namely the killing blow to the back of the neck that jaguars inflict on their prey. After finishing our last night off with one of our major targets I resigned to an hours sleep before our early leave in the morning.

Our time in the Amazon with Jose from Tropical Herping was exhausting but incredibly worthwhile. We were able to find species we had only ever read about and some we had never heard of at all. We witnessed behaviours and ecology that remind me why I am so fascinated by herps. The Amazon was an area on my bucket list and it certainly lived up to the hype. I will be returning sooner rather than later.

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