March 26/2025

 

It’s Official: There’s Another ‘World’s Largest Snake’

by Olivia Young

atlasobscura.com

2/ 29/ 2024

The cloudy swamps & creeping streams that cover vast expanses of South America harbor some of the most hair-raising wildlife on the planet: poisonous frogs, electric eels, deadly mosquitos, & grinning caymans are just some. The Amazon is no place for someone who is spooked by things slimy, scaly, or hidden under murky water with only menacing eyes & nostrils visible. And yet that’s exactly what Jesús Rivas has looked for when he’s waded through the wetlands of South America over the past 32 years.

Rivas, a biology professor at New Mexico Highlands University, is an anaconda expert. In his decades of research, he has collected hundreds of blood & tissue samples to expand our collective understanding of the world’s largest snake, ultimately to protect it against threats like human impact & climate change. With a team of fellow researchers composed of both academics & Amazonian Indigenous peoples, he has discovered a major divergence in the green anaconda, one of historically 4 anaconda species.

Green anacondas are the heaviest snakes on the planet & the second longest, after reticulated pythons. They occur in the wet tropics of South America, east of the Andes, from northern Venezuela to the south of Brazil. Until recently, the green anaconda was thought to be just one species, Eunectes murinus, but a newly released study headed by Rivas found out there are actually 2. The research describes major genetic differences between green anacondas in the northern half versus the southern half of their range.

“We got the first hints that [the northern] species was different from the southern one in 2007,” Rivas says. “Then we started the hard process of gathering samples from all over South America.” Even though the 2 snakes appear identical, DNA sampling shows a drastic genetic difference of about 5.5%. That’s a bigger difference than the one between humans & chimpanzees. When 2 or more species are classified as one because they are morphologically indistinguishable, they’re called “cryptic species.” This is the case for the green anaconda, whose northern & southern populations are virtually identical in their massive size (reaching lengths of 30 feet & weighing up to 550 pounds) & coloring (olive green with dark splotches along their backs & sides).

Bryan Fry, co-author of the study & professor at the University of Queensland in Australia, says the key difference between the 2 populations is the geographic range. Years of field work & sampling revealed that specimens studied across the northern part of the green anaconda’s distribution were actually of a sister clade of E. murinus, which the researchers have named E. akayima. Whereas E. murinus (the southern green anaconda) can be found in Venezuela, Trinidad, Guyana, Suriname, & presumably Colombia, the second species E. akayima (the northern green anaconda) inhabits Peru, Bolivia, & Brazil. The species stick to their separate zones except for in French Guiana, & the study suggests that country “might be a contact zone for these 2 groups.”

In 2022, Rivas, Fry, a local Indigenous leader, actor Will Smith, & the crew of National Geographic’s “Pole to Pole” series embarked into the Waorani Territory of Ecuador & found evidence that the northern green anaconda is present there as well. That Indigenous leader, Penti Baihua, & his son, Marcelo Tepeña Baihua, are listed as co-authors on the study, & Will Smith is mentioned in the acknowledgements.

“One key factor that allowed us to make the publication now is new developments in our understanding of the history of South America,” Rivas says. He clarifies that the 2 species weren’t always so different. They likely diverged millions of years ago as a result of a ridge that rose & geographically separated the north & south. Now that there’s data to support that the green anaconda is made up of 2 claves, researchers can begin to work out the unique needs of each so these enormous snakes can continue slithering about & dominating the jungle.

“The discovery of a new species is always important,” Rivas says, “as it informs us better of the diversity we have—& may lose.”

* Article & photos from New Anaconda Species Has Been Officially Recognized - Atlas Obscura

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