Never-before-seen footage captures moment scientists find new, giant anaconda species in Amazon

In 2024, scientists announced the discovery of a newfound anaconda species in the Ecuadorian Amazon. Now, in a new nature series, filmmakers have released nail-biting, never-before-seen footage of the moment they encountered the snake in the wild.

The footage transports viewers to the Baihuaeri Waorani Territory in the Amazon rainforest, where researchers were sampling anacondas in 2022 for a snake genetics study. In the video, venom expert Bryan Fry and actor Will Smith travel by boat with Indigenous Waorani guides along the banks of a murky river. In a small clearing, the group spots a gigantic anaconda, which the guides manage to immobilize so that Fry and Smith can take a piece of its scales.

The anaconda in the footage — which features in an episode of National Geographic's upcoming "Pole to Pole with Will Smith" docuseries — is a female measuring 16 to 17 feet (4.9 to 5.2 meters) long, Fry estimates in the show. There is a danger she might bite, says one of the Waorani guides who helps pin down the snake, even if green anacondas aren't venomous. Anacondas are constrictors, meaning they kill prey by wrapping their bodies tightly around it, suffocating the animal before swallowing it whole.

The scale sample and others taken in 2022 revealed that green anacondas, which were previously thought to all belong to one species, actually form two separate species: Eunectes murinus, the already-identified southern green anaconda, and Eunectes akayima, the newfound northern green anaconda.

"Finding a new species is so often not a case of actively searching but rather having rigorous scientific process in place so that serendipity can strike," Fry, who is a professor of toxicology at The University of Queensland in Australia, told Live Science in an email. "The research into the genetics of the iconic green anaconda is textbook in this regard."

Genetic analyses indicate that E. murinus and E. akayima diverged 10 million years ago. Since then, northern and southern green anacondas have accumulated thousands of genetic differences adding up to a whopping 5.5% of their total DNA. By comparison, the level of mismatch between human and ape DNA is about 2%.

As its name suggests, the northern green anaconda inhabits the Amazon's northern basin, which includes parts of Ecuador, Colombia, Venezuela, Trinidad, Guyana, Suriname and French Guiana. The southern green anaconda, on the other hand, is found in the Amazon's southern basin, which stretches across Brazil from Peru and Bolivia to French Guiana. Both species live in wetlands and rivers, spending most of their time submerged in water. Their olive-green coloring blends into their surroundings, which helps green anacondas ambush large prey such as capybaras (Hydrochoerus hydrochaeris), caimans and deer.

Green anacondas are the world's heaviest snakes, with some specimens weighing more than 550 pounds (250 kilograms) and exceeding 12 inches (30 centimeters) in girth. Female northern green anacondas grow the largest and heaviest, while their male counterparts have more slender bodies. This means female and male northern green anacondas hunt different prey and occupy different positions in the food chain, Fry said.

"Females and males live in the same environment, but they feed differently," he said.

The northern green anaconda is the fifth described anaconda species in the world — and there may be more hiding out there, Fry told Live Science. "Despite anacondas having a state of fame exceeding that of any other reptile, they are really poorly known," he said.

Knowledge of the northern green anaconda's existence is important in and of itself, but the difference in male and female diets could also give clues about the health of the ecosystem — and the people who live in it, Fry said. Female northern green anacondas feed lower in the food chain than males do, preying on animals such as deer. The males eat more predatory fish and caimans, meaning they accumulate more toxins leftover in the environment from events like oil spills than females do, he said.

Male northern green anacondas' diet resembles that of humans living in the Amazon. Therefore, the concentration of toxins in these anacondas provides an estimate of the pollution that people are exposed to — and that pollution is high, Fry said.

"The concentrations of the heavy metals cadmium and lead, potent endocrine disruptors that are the signature of oil spills, were over 1000 percent higher in males than females," he said. "That is not a subtle difference. That is a warning flare."

In light of these findings, Fry is developing a wild food guide for the Waorani. "Recommendations will include pregnant women and young children avoiding top-level predators likely to carry higher contaminant loads, such as arapaima and arowana [two types of predatory freshwater fish]," he said.

"Pole to Pole with Will Smith" premieres Jan. 13 on National Geographic, and Jan. 14 on Disney+ and Hulu.