Once Extinct in Argentina, Giant River Otters Return to the Wild
July 2, 2025
Giant otters © Matias Rebak, Rewilding Argentina
The release of a family of giant river otters marks a rewilding milestone in Argentina, where the last breeding population was sighted 40 years ago. The endeavor to bring back the apex freshwater predator from national extinction has been made possible by the provincial government of Corrientes, Argentina’s National Parks Administration, and Rewilding Argentina, the offspring organization of Tompkins Conservation, in collaboration with international organizations.
Endangered worldwide, the giant river otter, Pteronura brasiliensis, is making a powerful comeback in Argentina, where the last population was sighted 40 years ago. Charismatic and playful, the world’s largest otter measures up to five feet, nine inches (1.8m), weighing up to 72 pounds (33kg). A family of four otters, including two pups born in captivity, have been set free in the 2-million-acre protected wetlands of Iberá, marking the first worldwide comeback of this species in a habitat where it had been rendered extinct.
“The giant river otter is a keystone species and the top aquatic predator of the wetlands,” says Sebastián Di Martino, Conservation Director of Rewilding Argentina, “Its presence regulates populations of other species, and thereby keeps aquatic ecosystems healthy. In times of wildfires and drought, the contribution of keystone species to the ecosystems becomes especially important.” Located in Northeast Argentina near the borders of Paraguay and Brazil, the Iberá wetlands are one of South America’s largest and most important watersheds, crucial to the wellbeing of humans and wildlife alike.
The giant river otter reintroduction program of Rewilding Argentina, the offspring organization of Tompkins Conservation, began in 2017. The program has spawned many rewilding firsts: obtaining suitable mates from zoos around the globe, devising a regulatory precedent for the international transfer of wildlife for release, breeding captive pairs to form the family units that live and hunt together in the wild, and inventing specially-made harnesses with GPS transmitters to track the individuals in the wild.
For Kristine Tompkins, President and co-founder of Tompkins Conservation, the release, which coincides with her 75th birthday, is an important milestone. “The giant river otter’s return marks a huge win for the communities of Northeast Argentina, all the park visitors, and the natural world. As we face the largest mass extinction this planet has ever known, this is our most urgent task: helping nature heal.”
The giant river otter’s disappearance in Argentina was the result of illegal hunting and habitat loss. To aid in the species’ permanent recovery, Rewilding Argentina continues to prepare multiple otter families for release in the Iberá wetlands and the Gran Chaco. According to Di Martino, it’s part of a larger vision of ecological recovery: “By repopulating the giant otter in Argentina, we can begin to restore connectivity between isolated populations, which would help bring back this key species throughout the heart of South America.”
Giant otter © Matias Rebak, Rewilding Argentina
BACKGROUND
Located in Corrientes Province in Northeastern Argentina, the two-million-acre Great Iberá Park is comprised of Iberá Provincial Park, together with Iberá National Park (400,000 acres), created in 2018 by donations from Tompkins Conservation and Rewilding Argentina to the Argentine state. The wetlands are located at the center of a great subtropical plain surrounded by Paraná Atlantic Forest, Chaco Forest, open grasslands, and thorny shrublands.
Rewilding Argentina is reintroducing nine other species to the wetlands, including the jaguar, the top terrestrial predator, and red-and-green macaw, which acts as a seed disperser for native vegetation that is now in short supply. Rewilding is bringing a regenerative economy to Iberá through ecotourism with wildlife observation, now a principal income for communities in Corrientes province. Tompkins Conservation has spent nearly three decades rewilding the Americas with big, wild, and connected landscapes where human communities, animals, and plants can thrive. Collaborating with public and private partners, the organization has driven the creation of 16 parklands, protecting 15.1 million acres.
Nima, Coco, and pups © Sebastián Navajas, Rewilding Argentina
MEET THE FAMILY
The mother of the group, Nima, was donated from the Madrid Zoo in Spain. Her mate, Coco, was the first giant river otter to join Rewilding Argentina’s reintroduction program in 2019 and came from Givskud Zoo in Denmark in 2020. Their two offspring were born on November 6, 2024. The release project is aided by the Ex-situ Programme of the European Association of Zoos and Aquaria (EAZA) and the expertise of Projeto Ariranhas in Brazil. The giant river otter is listed by the IUCN as endangered. The liberation of the giant river otters in Iberá marks the first time Argentina has restored an extinct mammal.
A driving force to curb the worldwide climate emergency and the biodiversity crisis, Tompkins Conservation protects, rewilds, and defends land and marine ecosystems in the Southern Cone through collaborating to create national parks and rewilding key species. Working with public and private partners, the organization has helped to create 13 national parks, protecting 14.5 million acres. The goal is to restore a healthy planet with big, wild, and connected landscapes where animals and plants can thrive. This also means helping to build robust communities that benefit from a healthy natural world.
Kristine McDivitt Tompkins and Douglas Tompkins (1943-2015) founded Tompkins Conservation after leading iconic American clothing brands—Kristine as longtime CEO of Patagonia Inc, and Doug as co-founder of The North Face and Esprit. Changing course in the early 1990s to focus on conservation, they became two of the most successful conservation philanthropists in history. After Doug lost his life in a tragic kayaking accident in 2015, Kristine has continued to build on their foundation. She is now the president of Tompkins Conservation and a UN Environment Patron of Protected Areas.
A 501(c)(3) public charity, Tompkins Conservation carries out conservation projects through the nonprofit network of Rewilding Chile and Rewilding Argentina.