Conservationists in Argentina are celebrating after the sighting last week of a wild giant otter, an animal that was last seen in the 1980s and believed to be extinct due to habitat loss and hunting. The otter was spotted swimming alone on the Bermejo River in Impenetrable national park, located in north-east Argentina.

Sebastián Di Martino, director of conservation at Fundación Rewilding Argentina, a conservation organization, captured the photo on his phone while kayaking on the river. He told The Guardian it was “a huge surprise” and that he was “incredulous,” wanting to “rush back” to tell the other members of the organization. 

The giant otter (Pteronura brasiliensis) is the largest otter species in the world, measuring up to 1,8 meters and weighing about 33 kilos. It can be found in large rivers and swamps in northern and southern South America. They have been nearly wiped out, first because of their fur, and now because of extractive activities happening in their habitats. 

It’s considered extinct in Argentina, with the last sighting reported in 1980 in the province of Misiones. In the Bermejo River, where it was now spotted, it hasn’t been seen for over 100 years. The closest registered populations live in the Paraguayan Pantanal, 1,000 kilometers away, so the otter could have arrived from there. 

“Giant river otters, as top predators, exert a regulatory influence in the aquatic ecosystem,” Di Martino said. “It’s a regulator of fish populations, which contributes to the health of aquatic ecosystems. It’s a spectacular animal, and it’s enormous. They are trusting and curious. To share the environment with them is marvelous.”

Such is the importance of otters that the conservation organization has long been working on plans to reintroduce them. They first brough in a mating pair from Denmark and Hungary, named Coco and Alondra, soon to be released in Argentina’s massive Ibera wetland. Another otter, Nanay, recently arrived from Switzerland. 

Rewilding Argentina has also been working to bring back top predators and other species to their native habitats. Six jaguars (Panthera onca), the largest predator in South America, were released earlier this year. The organization will continue working with the guanaco (Lama guanicoe) and the yaboti tortoise (Chelonoidis carbonaria). 

The organization helped create the Impenetrable National Park in Argentina in 2014, where the otter was recently spotted, alongside Tompkins Conservation. The Park has 1280,000 hectares of native forests and waterways and is located in the Gran Chaco Forest, an area that has been subject to large levels of deforestation over the years.  

“For us, the importance of this sighting is that we’re reminded that we have to protect more of this gem of biodiversity that is Impenetrable national park,” Di Martino said. “The Bermejo River, where this otter was found, is full of illegal hunting and fishing activity. There needs to be more supervision, but also the river has to open up to activities such as tourism.”