New Species of Anaconda Discovered in Orinoco Basin

An international team of herpetologists led by New Mexico Highlands University and University of Queensland scientists has described a cryptic new species of anaconda from the remote Amazon.

Anacondas (genus Eunectes) are a group of aquatic snakes endemic to the east of the Andes in South America.

These large-bodied snakes inhabit lowland rivers and wetlands; they have the typical adaptations for an aquatic lifestyle, such as nostrils and eyes located dorsally on the head, and displaying a dorsal coloration and pattern that blend well with the aquatic vegetation.

Before this study, four species were recognized in the genus, with Eunectes murinus representing a sister lineage to a group composed of Eunectes beniensis, Eunectes deschauenseei, and Eunectes notaeus.

The largest of these species, Eunectes murinus, or the green anaconda, occurs in most of the tropical regions of the continent, including the basins of the Amazon, Esequibo, and Orinoco rivers, and several smaller watersheds.

The other three species are smaller than Eunectes murinus and are distributed within or adjacent to the distribution of Eunectes murinus.

The recently-described species Eunectes beniensis, or the Beni anaconda, has a distribution restricted to the Beni region of Bolivia.

Eunectes deschauenseei, or the dark spotted anaconda, is distributed in the northeast of the continent. It is found from the Amazon River delta in Brazil to French Guiana and possibly Suriname.

Eunectes notaeus, or the yellow anaconda, has a distribution to the south of Eunectes murinus including the Pantanal, Chaco, and other hyper-seasonal areas of tropical and subtropical South America including Brazil, Bolivia, Paraguay, Argentina, and Uruguay.

“Our team received a rare invitation from the Waorani people to explore the region and collect samples from a population of anacondas, rumoured to be the largest in existence,” said University of Queensland’s Professor Bryan Fry, co-lead author of the study.

“The indigenous hunters took us into the jungle on a 10-day expedition to search for these snakes, which they consider sacred.”

“We paddled canoes down the river system and were lucky enough to find several anacondas lurking in the shallows, lying in wait for prey.”

“The size of these magnificent creatures was incredible — one female anaconda we encountered measured an astounding 6.3 m (20.7 feet) long.”

“There are anecdotal reports from the Waorani people of other anacondas in the area measuring more than 7.5 m (24.6 feet) long and weighing around 500 kg.”

Named Eunectes akayima, or the northern green anaconda, the new species occurs in the Orinoco Basin.

“Eunectes akayima diverged from Eunectes murinus almost 10 million years ago, and they differ genetically by 5.5%,” Professor Fry said.

“It’s quite significant — to put it in perspective, humans differ from chimpanzees by only about 2%. This discovery is the highlight of my career.”

“The Amazon continues to face alarming ecological threats,” he added.

“Deforestation of the Amazon basin from agricultural expansion has resulted in an estimated 20-31% habitat loss, which may impact up to 40% of its forests by 2050.”

“Another increasing problem is habitat degradation from land fragmentation, led by industrialized agriculture and heavy metal pollution associated with spills from oil extraction activities.”

“Forest fires, drought and climate change are also notable threats.”

“These rare anacondas, and the other species that share this remote ecosystem, face significant challenges.”

“Our next research project would focus on heavy metal pollution in the Amazon,” Professor Fry said.

“It’s not only these gigantic snakes that are facing environmental threats, but almost all living things in the region.”

“The discovery of a new species of anaconda is exciting, but it is critical to highlight the urgent need to further research these threatened species and ecosystems.”

“Of particular urgency is research into how petrochemicals from oil spills are affecting the fertility and reproductive biology of these rare snakes and other keystone species in the Amazon.”

The discovery of Eunectes akayima is described in a paper in the journal Diversity.

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Jesús A. Rivas et al. 2024. Disentangling the Anacondas: Revealing a New Green Species and Rethinking Yellows. Diversity 16 (2): 127; doi: 10.3390/d16020127